With this amount of explaining it just goes to show how passionate you are with your company and workmanship, keep going an ignore the haters, beautiful sheds🤯👍👍
for those people interested in the hybrid roof discussion there are 3 key potential issues: 1. Difficulty of creating a 100% full vapour control layer on the warm side. 2. Thermal bridging 3. Hybrid designs are untested by the insulation manufacturers, so architects / surveyors / building inspectors don't like them and don't specify them. However, in the context of a garden office, the construction on this video is, in my opinion a perfectly valid compromise. Yes there will be a bit of thermal bridging, but is that likely to cause condensation issues? Timber is a reasonable insulator so the chance of the inside face of the joists being below the dew point is pretty rare. The somewhat bigger potential issue interstitial condensation due to vapour getting to the underside of the OSB - Ideally foil tape should be stuck on around each joist and covering a bit of the celetex - that creates a vapour barrier. To be honest, on house extensions there is far more risk where a cold roof has been specified and the roof is not adequately ventilated (or downlighters penetrate through the insulation to the cold space. In these situations a hybrid roof with say 100mm in between and 50mm cover would be a far better option. I think this Oakwood garden rooms channel is fantastic, some great ideas and I bet the customers are very very happy. I used to manufacture and install top end hardwood orangeries, so much of this construction is familiar.
When I seen this notification pop up I initially rolled my eyes , here we go again I thought 🙄 But having read this unbiased comment I’ve gotta say, this is constructive and well written. Thank you for your input and I will definitely be using the foil tape going forward. I appreciate it’s not perfect but I’m these situations it works. Thank you for your input 👌
@@thegardenroomguru many thanks for your reply, having read through all the comments about this video you posted, I thought I'd add my 2pence worth which hopefully provides some balance. I can see from your videos you have clearly honed your construction methods and details to produce a great product for efficient commercial production and it's very generous of you to share.
There was documents from LABC maybe 10 years ago that had some variants of a hybrid roof that had insulation between, pushed to the top, then ABOVE the joists. Thinner than a warm deck, doesn't need venting, but I agree not one other architect I met wanted to work with it - insurance purposes.
I’ve heard you make a point about people trolling and leaving abrasive comments about your clips. All I got is admiration and thanks for you taking the time to do these videos and to educated people like me a bit. So thank you and carry on. Cheers. W
I’m not a builder, joiner or anything to do with the construction industry but I love your bluntness, well you are Yorkshire, your efficiency of working and the finished product. Keep on keeping on !
Hi Liam I’m a general builder and have used your system and I can assure others that it does work, no issues ever in the many buildings I’ve done in the south west. Keep up the good work.
Mirroring other comments, ignore the haters, leave them to dwell in thier pits of misery. Your vids are informative, concise and occasionally funny. They break the monotony of other posters formats and I for one look forward to them. So a big 👍 for cracking builds and videos.
Completely get it. Haters will hate. Ignore the trolls. You've said it enough now if they still talk shit then they obviously can't be bothered to look at your videos explaining why you do it that way. They just want to get a reaction. Plenty of us really appreciate you taking the time to upload your work
I'm in the early stages of a garden room build right now (almost cleared the ground, but have a bunch of materials ready to go). "tradies" have been telling me to vent my cold roof and the additional costs are ridiculous, not to mention the fact I'd need to lose internal head hight. Thank you for this video, and for all your videos. They've been a great source of inspiration and information for me as I've been planning and designing my room.
@dlvulpes1048 I'm all done now bud, this comment was over 6 months ago. My garden room is complete all except for the external cladding. Moved in last week 😊
Thank you for sharing this. I built my garden room with 90mm rafters to keep under the height limit and watching how you guys do the insulation has given me confidence to do the same in my build. I have first fix electrics coming this week so will be able to get insulation and membrane installed next week in time for the weather getting crap.
is your ceiling sagging if you used 90mm rafters? Using the span tables 90mm on 400 centres gets you a span of less than 2 meters? What are the dimensions of your room?
@@dugbert9 My ceiling rafters are C24 90x50 and are spanning a little over 2m wall to wall. They are certainly on closer than 400 centres and absolutely solid so far but that's to be expected as the roof was engineered and I just followed the diagrams I had been given.
Used this system on a flat roof garden room with 8 x 3 joist put and angle fillet on top of the joist to give the roof some fall for the water, full filled with 200mm insulation ,vapor barrier and foil backed plasterboard. Was so worried about moisture after 8 years took a piece out to have a look and was as dry as a bone.
The one problem that hasn’t been highlighted is interstitial condensation. Using the hybrid solution shown in the video will move the dew point below the decking and even with a vapour barrier correctly installed sweating below the decking will occur. It is also worth noting that vapour barriers, even if installed correctly, are only effective below 60%RH. The guy is pretty knowledgable and his builds and videos are very helpful. However, this roof make up wouldn’t work and 50mm ventilation space would have to be incorporated to prevent future issues.
I’m not sure I agree. I’ve not found any tests performed that show sweating would occur. Cold roofs require a flow of ventilation and that is so often compromised, I would argue a hybrid roof will perform better. Either way, it comes down to attention to detail more than the choice of warm or cold
I think you are both right! There will be condensation, but, it is pressure treated lumber and it will eventually drip or evaporate away. If you look at what they do in America, it is very similar to this and they build everything out of wood. On another note, you could leave that 20mm ventilation over the cellotex or put 70 or 80mm insulation. The amount if insulation required now is just ridiculous! The difference between a U-value of 0.22 (100mm PIR) and 0.32 (70mm PIR) is 37W for a 20m2 roof with 20 degrees temperature difference. A human existing / resting produces 100w of heat.
🏆 Happy to hear it explained so plainly and couldn't agree more on other people's designs which seem to magically come under 2.5m despite 8x2s rafters! I've been going mad trying to work out my heights but this certainly helps knowing I can do away with the cold roof ventilation gap and so get my services in easily. Do you ever have roof lights/sky lights in your buildings and anything to be aware of? I would love to have one on my little 3x3.5m studio but feel like there will just be issues with moisture, perhaps as there will be little space between cold rooftop and warm air near the glazing where the trimmers will be
Glad to hear you tell folks about the 2.5m permitted dev taken from the highest point on top of slope. Makes sense when building on a slope. Finally got out of the ground tonight so base joists & hangers tomorrow! Great update bud
Cut into the slope and get more height to play with. I've got a 400mm fall where I'm planning to build so as understand it I can drop my base level and still measure the 2.5 from the heighest original ground level, so getting more like 2.9m.
@@jmccoy555 - If you do dig down, put some measures in place to cope with the 1 freak day of heavy rain in a 1000 days - the last thing you want is to get them floor joists soaked or even worse end up sitting in mud after a few years... Also - I recon a pinickety inspector would take the level at which you have dug down to build upon to be the ground level from which they will measure.. I would only cut in if you are doing so to reduce the extent of which the lowest ground level threaded bars are protruding from the ground level... The head height in Liam's builds is fine, why push it to gain a few cm and run the risk of being forced to pull it down after a few weeks, months or years...
@@TheStumpy3496 it slopes 3 ways, 400mm across the diagonal and 200/300 on the corners and continues to fall in all directions so no chance of a mud bath. Got to drop something or the front door will be in the air!! The regs quite clearly say its all measured from original ground level. It's actually quite a well documented loophole. www.google.co.uk/url?sa=t&source=web&rct=j&url=publicaccess.wokingham.gov.uk/AniteIM.WebSearch/(S(lkgvbv45pljxp545tp4dim45))/Download.aspx%3FID%3D92803&ved=2ahUKEwiioeTngeLrAhUDiFwKHbUhDUUQFjAPegQICBAB&usg=AOvVaw23YIP0ATx5nNXr52iGuNpK
Great explanation, I bet 90% of people that moan about your roofs have never even layed one,I done a flatroof on the main scientology building in East grinstead and that was a hybridu because it was south facing they speced the roof with 8 inch of insulation above deck but with that amount we would be upto the gutter on the adjoining roof, So I put to them 4 inches above and 4 inches in between and that's what we went for, It also cut the fixing bill by about 70%,you do a great job your a bit swift for me but I love watching your vids
Blimey Liam, the dreaded AJ. I like the hi-bred roof myself or it has to go through planning to raise the roof. I am a general carpenter/joiner. As I have only done four of these garden rooms, I hang on to every word that you have said and It’s served me well many thanks.
Well done! You have described that perfectly. Anyone who is in the trade will understand you. People spend too much time looking at specs and varying ‘recommendations’ from Internet forums etc. Listen to the tradesman that do this day in day out and have years of experience not keyboard warriors. Great work chap. P.s don’t pander.
Aye, ignore the haters. I really appreciate that you've gone the extra mile at least three times now, explaining how you do the roof, and why. Keep the vids coming, you're doing great stuff.
It might work for this level of building but it will defo condensate for two reasons, first you have cut the insulation in the zone for the lights therefore a difference in temperature especially over night. Also the joists are in direct contact with the cold and not isolated/insulated. Timber is no longer calculated at zero as they do conduct, even if only slightly. Therefore the ambient air zone is compromised and condensation will pool on the back of vapour barrier. It is important to provide people with rounded knowledge, but get this is only a garden room. I have built many passivehaus timber frame homes so have maybe more understanding than most in this area. Hope this input helps someone
I would agree - the vapour barrier is cut which will allow moisture to penetrate. I would have thought the ideal would be 70mm of insulation as he has tight to the OSB - ideally glue foamed to the OSB. Then a 50mm air gap, then 38mm of insulation backed plasterboard on the ceiling joists. Not sure the vapour barrier adds much in this case as you would be cutting through it anyway for multiple spots. The 50mm air gap could be vented both ends which is ideal. Thoughts? Yes you lose 26mm head height but worth it. On the floor, you don’t need an air gap if you have a membrane. So membrane, then 50mm insulation is sufficient, then ply, then your floor covering of choice. I just wanted to check before I do mine… so any reactions would be great.
@@glassdomedesign if you ventilate in-between the 70mm PIR and 38mm back plasterboard then the 70mm loses its insulation value. The 70mm would need to be to the lower side of the rafter against the 38mm and then to ventilate in the 50mm gap above.
Thanks for that mate VERY helpful. I know nothing about building anything but got a lot of common sense and the way you explain stuff makes perfect sense to me. Good on yer.
excellent videos thank you i may or may not have made a mistake in my floor design, time will tell i guess i used a steel base from uroof ltd bonded with ct1 and screwed galvanised steel seets to the bottom and sealed all holes and sat the whole thing on ground screws, bolted and screwed each section together filled with recycled plastic insulation, then run 25mm steel box box sections along the floor panels at 400ish centres in the opposite direction to steel floor joins, 25mm pir between, covered in joint tape, then a dpm over the lot and wrapped down over the outside of the steel , then 18mm ply for the floor
As usual, makes sense to me. For all the haters, they could always add foil wrap into the squares you cut out the lights then seal to the surrounding insulation. If you foil tape where the lights come through the vapour barrier that would solve their moisture egress issue too?! Keep up the good work, loving the tutorials 👍👍👍
Excellent explanation. Ive literally just finished my roof timbers and chose this system just to get the extra head room inside, as a warm roof just robs you of height. Well done great vid.
Everyones an expert in the building industry!! And on that note, a better way of doing the hybrid roof system would be to wrap the moisture barrier round each joist void so it’s sandwiched between the insulation and the ply. Also that way you won’t need to cut a hole in it when you put your led lights in. 😂😂😂
So, why not put the insulation lower down in the joists leaving a (small) gap between the insulation and the underside of the roof that can then be ventilated. Is that an approach that would provide some protection against condensation ..?
Hands down...if I could afford one this is the only guy I would trust to build a garden building for me!! And as I can’t afford you I’m taking every tip I can from the channel and building my own!lol😊👍🏼 really appreciate you taking the time to show us how it’s done properly mate
Totally agree mate as long as its low occupancy there will be no problems with condesation....its not like people are showering bathing or cooking in these rooms at most they sit in them and get drunk and watch tv ...well explained 👍🏼
Don't worry William as there are haters everywhere but professionals like you are not so easy to find.People should take a leaf out of your book and get on the tools to see how easy it is (or is not) . I spent 14 years in the wines and spirits industry and was forced out of my job due to Covid. DIY was my passion so i have picked the tools and put them to work.There are jobs are out there if people can be bothered to work instead of trolling those who do...keep up the good work!!!!
Nick, I see you often in the comments, thank you for your support and always your advice and kind words, it’s friends, and I say friends, because of see you all as friends, tgat I keep posting 🙌
Nick Demetriades just read back my English 🤦🏻♂️seriously, I’ve built a community and following from nothing in a small period of time. I’ve a passion for what I do, I thought I was alone. Then you guys appeared! I’m blown away, I’ll hit 20k subs next month, channel 4 and 5, have emailed me. It’s amazing and quite frankly I’m still in awe!! If you ever need anything answering just ask and if I don’t reply, call me 💪thank you, and any of you reading this that folllow me xxx
@@thegardenroomguru Don't worry about the English mate..cant believe that you have so many followers and yet you can tell from the quality of info its a no brainerAbsolutely no surprise about C4&5 wish you all the best with that and i know you will smash it
If the insulation is 1mm out then there is a condensation hence black spots that's why the bigger the air gap above the insulation the less chance of air settling 🔨
Hi Liam, I fully agree the hybrid roof in this use case is the best option. I think councils should be updating the planning restrictions of 2.5m. If they increased this even to 2.65, it would allow for a warm roof. This would be environmentally friendly as it would reduce long term roof replacements, although in the sort term I can see it having a negative environmental effect due to the increased materials required, but does seem that 2.5m is an arbitrary value with little consideration as to it's impact on the design of a building.
Always interesting and learning alot, great of you to share your knowledge and methods. I plan to build one myself in the future and without your vids I wouldn't even entertain the idea. Big up Geez 😊
If you use foil back plasterboard and seal the back edge of the joints with Cilicone they act as a vapour barrier, that’s how I do mine. I also do my roof to your method since seeing your videos and it works great. I’ve never looked back. 👍
What your doing is really smart to stay within the hight limits personally I wouldn't bother with the vapor barrier on the inside if your gona cut holes in it for sockets downlights etc . Iv built a few houses and used blower prof on the outside osb and tape the joint s Fewer penatations . Your garden room s look great
What’s the moisture barrier for if you’re cutting huge holes in it for a spotlights!? You can’t use spotlights in a cold roof because you break the moisture barrier
I came across this video as I'm researching how to deal with unvented cold roof. I'm building a summerhouse and am up against the height limit as you describe. I'm of the same view as you; low occupancy and in my case, as one wall will be a bifold door and probably open when occupied, there will be very little warm moist air in the room anyway. Most of the advice on domestic construction is aimed at occupied dwellings and designers have to work on worst case of family taking lots of showers, cooking, drying clothing so high moisture levels. I've also come across research from Germany that backs up the cold roof but with no cold air void (as your build) although this requires attention to detail and ensuring no air can flow form inside through the roof deck. The German research also criticises the assumption that air flow in a vented gap will actually remove the trapped water; if there's insufficient air flow then all you've left is an uninsulated air void for cold moist air to condense on the timber. In my case I'll be fully packing the void, VCL and also using a spray applied sealant on the underside of roof deck at any possible air gaps. German research also recommends using a smart VCL (which can change permeability and allow any moisture trapped in the roof to vent down into the space in correct conditions) but it cost more than a standard VCL so I'm not using it but I am installing a MVHR with humidistat to deal with the odd occasion when the room may be used with doors closed and a few persons in it. I'm a professional in the construction industry (Site Engineer with Construction Degree and over 25 years of experience) and yes, a warm roof would always be a best option but sometimes it not possible. My thought are if the roof structure has no air leaks then how can moisture vapour (which can only be airborne) get into the cold roof space in the first place?
Hi Andrew Not sure if you have seen a later video where I talk about the report a viewer did on the hybrid roof we do. It states that there is no risk of mould build up snd any moisture that does occur will dissipate in the summer months. It concludes the hybrid roof we do will not fail under the conditions we install 👌
As far as I know, you are not meant to cut the vapour barrier around the lights as you're defeating the purpose of it? In fact, Roger from Skill Builder mentioned this in one of his videos? Can you please explain?
Hi I agree with your idea. All this warm roof cold roof stuff. It all so OTT to me. So you have to air vent between the joist. So in December when it’s freezing cold isn’t that air gap going to get cold and thus making the ceiling cold? Hasn’t nobody thought about that?
A would like to see a revisit few years down the line to visually see what roof is like behind insulation the rubber roof itself gets warm in hot days, it doesnt matter about low amount of people in it the venting to the underside of ply is to cool the rubber or felt on hot days by blocking off eves your goin to make it condensate behind insulation just my opinion of course i also am a builder and roofing contractor for 25 years
@@thegardenroomguru anywhere you have no foil tape on is somwhere hot and cold ambient temp can mix and escape ,wasnt judging meerly sharing knowledge from jobs we have been called to remedy and sort
Im still not sure how to do my shed ceiling. Lots of conflicting information. It seems that people in the UK at least, are convinced it will rot and fall apart if i dont cover the eaves in 50mm vents, because enough warm air will leak past insulation, tape, sheets, and foam. But the air flow through a small gap between timbers somehow wont disperse the torrent of wet air coming up from my mostly unheated shed. Maybe people are just overcomplicating things
Thanks for the videos...they're really useful. Very clear. Now, I get that the air below the insulation is ambient temp so no condensation, which makes me wonder.. do you really need a moisture barrier? (Especially in a low occupancy room eg home office) I'm not saying you don't. I'm just wondering why.
Hi there I’ve just built a single skin brick shed/bar. The building up rubber roof on and doors/ windows in. When it’s cold there was loads of condensation on the obs roof in the morning and I’m wanting to know what’s the best solution to stop this. The hybrid roof tour on about or adding air bricks to my brickwork. I wasn’t planning on plastering boarding it or anything like that just paint the inside
Just discovered your channel & couldn't subcribe fast enough! What a well built room! Wish we built this way in Australia. Interested in a working holiday?
Enjoyed the video, and your clarity of thinking & whiteboard illustrations are easy to follow. One question though: I follow your thinking re the ambient temperature air gap above the ceiling but below the insulation, but why not completly fill with Foam insulation leaving no air gap - no air, no moisture vapour to condense out? What am I missing?
Why have any air gap at all? Serious question. Does it help insulation? I used a foil based membrane, so I guess it would be defeated by contact, as far a radiative resistance is concerned.
Great vid, Is this is why you can successfully frame and spray foam a shipping container with air gap on inside at ambient temp, then moisture barrier and ply or Osb with no sweating issues?
Thanks for demonstrating this and your excellent videos - they have helped with my build! I am going to use this approach but use the 20mm space above the insulation instead. There would then be a further added benefit if this slim area could be ventilated... right?
For a roof to qualify as a hybrid cold/warm roof it needs to share characteristics with both - otherwise it's not hybrid. The defining characteristics of a warm roof is that the air/vapour barrier and the insulation is placed above the joists and the air/vapour barrier isn't broken by lights or other penetrations. Your roof place all the insulation below the sheeting (between the joists) and the air/vapour barrier below the joists. This is the defining characteristics of a cold roof. A cold roof does not have to have an air gab to be a cold roof but if you don't want to get into trouble you need to vent the bottom of the sheeting and this is where the air gab comes into play. If your construction was safe then every cold roof would be done that way - and they aren't. More over the air gab below the insulation doesn't serve a purpose. Filling it with insulation would make for a better insulated roof and would be a better option. But your construction is missing the venting of the sheeting and is therefore an unsafe construction. For it to be a hybrid cold/warm roof you would need to place a big part of the insulation above the joists. In my climate zone I would think that having 2/3 of the insulation above the joists and air/vapour barrier would be OK and you could place the rest below. I don't know what ratio would work in you climate zone. Hope this helps...
Agree completely. You can't assume that no moisture will penetrate the moisture barrier and so must vent above with this design. What we seem to have here is simply an unvented cold roof similar to those often found on other youtube videos where rot has formed. Seems like quite a risk just to avoid a pretty simple planning application.
@@thegardenroomguru That's interesting. I'm not doubting that this design can work, and I do take your point that this is the ultimate aim so who cares. But I am something of a pedant with this stuff having tried to alleviate condensation issues in my victorian terraced house, and at least on paper, something doesn't quite feel right with your design. On the other hand, I agree with a point you made in another vid on SIPs, although I suspect the key difference there is air-tightness within the SIP. I fully appreciate the effort you're going to and think the vids are great, but I remain sceptical that this design would withstand a high-occupancy rate / cold winter combo. Would be very interested to see some temperature measurements from within the fabric... told you I was a pedant ;)
Totally get you, I do state that these are low occupancy rooms and if we do an annexe for example where living accommodation and bathroom are included then we would use a warm roof as of course planning would of been applied for so overall height would be not an issue as it is with these rooms
@@thegardenroomguru That you build unvented cold roofs doesn't mean that all of them will have mould or other moisture related issues after a few years and that one of your unvented cold roofs doesn't show mould or other moisture related issues after a few years doesn't mean that none of them will after say 10 years...
Your likely to get cold bridging through the joists. And issues where you reduce the insulation thickness for you lights etc. Although in principle I have no issue with your proposal. 25mm continuous insulation over the rafters, then plywood would be better. Reality is dormers were made like this for years with very few issues. The vapour barrier is the critical item.
Hi, great channel and great content. I have a question that no one can seem to answer. The bottom of my garden has steps leading down to a lower section (I believe the retaining wall is around 3ft high). I would like to build a garden building in this space. So do the height restrictions apply from the ground of this section or from the ground of my main garden?
The biggest issue I have is the fitting of down lights introduces holes in the construction with very little insulation above them. I'm not qualified and not in the trade. Built my own warm roof and sacrificed a couple of inches headroom.
Bloody great video. Even numpties like me can follow it. Just doing this in my roof of my garden room at the moment. Can I assume it is the same principle for the walls? I've got cladding, then breather. So the insulation board would sit up against these two layers. Cheers from Sunny Devon!
👌this is how I built mine. Only prob I seem to be having is a slight bit of condensation on my laminate floor in the corner at the skirting board I think it's due to ventilation i have a oil filled radiator and 2 x 4" vents I'm not sure if this is enough its 3x3 garden room
It’s an issue at this time of year due to levels of insulation and moisture held in warm air, soon as it meets a cold area it condensates. A dehumidifier will work wonders mate
@@thegardenroomguru I have just bought a 300ml dehumidifier and its collecting moisture. Do you think I need more vents or will 2 be enough. Love your work by the way 👍
It’s two more than we put in mate, we gave trickle vents on the glazing units, it will always collect water mate, it would if you put it in your living room, it’s just in the air, becomes apparent at this time of year
hi Liam - regarding span..you are using a 120mm joist in this example. Looking at the span tables that would give a max span of just under 3 meters. So I assume the bigger the garden room, the taller the joist and therefore the threat of running foul of the max height of 2.5. Are the span tables over egging the pudding for a garden room? I ask because I am worried about my ceiling sagging as I am under spec against the tables. I have fitted a warm roof as the building is inside a big agri building itself and it's farily lightweight as I have topped it with a tarp, not felt or rubber. Am I worrying too much??
I'm building a basic garden shed and I'd like to connect the roof vapor barrier with the wall vapor barrier. I'm leaning towards the hybrid solution because then it's very easy to connect both. Most people recommend a warm roof but then it's a lot of work to add vapor barrier strips between the joists. Do you know a simple way to do this? If I would opt for the hybrid solution. The space between the IPS insulation and is there a max/min height I should take into account?
Great video, could i use Rockwool type batts instead of the rigid boards you have used. I understand they will be lower insulation values but Im thinking from the condensation point of view cheers
I have a fiberglass flat roof with 2 roof lanterns and would like to know if I can use breathable vapour membrane between the insulation and plasterboard to prevent condensation....its a brick building. Thank you
Hi William, Great video once again. Please could you advise what you would do for the roof if you were putting a hot tub in there with half height walls on the front and sides? I am not planning to plaster or anything and wondering what to use for the ceiling? Regards, Simon
A big problem with all insulation calculations is how the insulations manufacturers have the energy loss calculated. If you put reflective insulation directly on a hot plate then that insulation will absorb heat more than if it was given an air gap in front of it. This in itself will change how ambient temperatures in front of the insulation or behind plasterboard are. When you ask Celotex about service voids compared to for insulated plasterboard that overall has the same thickness of insulation, they will tell you that it is the same. Which is not true.
A neighbour did this option 3 years ago, they've just had it ripped off because of the damage the moisture has caused. That being said I'm slightly tempted to try your method but wondering how long you've been doing it this way? If it's fairly recent then I'm slightly concerned
Hi William ... All cold deck info tends to be based around habitable areas. Thanks for clarifying the use of cold deck for garden rooms and confirming what my father in law constantly says about limited condensation risk. Can I ask about heating and with an under insulated raft slab, would you suggest underfloor electric heating or convectors or both? ... Used for office working 5 days a week, size is 12m2 with bifold doors
Well explained mate,always informative and you clearly know what you’re doing. I’m looking at building a woodworking workshop in my garden to replace my old garage,and looking at 30 square meters floor space and using every available and legal height dimensions I can,but I’m lead to believe I’ve got to have the new build at least 2 meters from from a boundary,it’s doable but leaves a load of empty space around it. Do you provide a design service? I’m based in north Manchester . Keep up the great videos,onwards and upwards.👍
This roof is fine because the due point is going to be located in the middle of the 100mm insulation where there is no room around it for air to condense, there theoretically could be a tiny amount of condensation around the due point location in the insulation if it isn't cut tight, but hardly worth worrying about. A better solution might be to fill the cavity completely with spray foam insulation which would completely remove the possibility of humid air buildup.
Exactly mate if you had any issues with your methods like moisture or condensation issues, they would show up within a few months. The fact they haven't and you're not being called back to jobs and your channel is growing means what you're doing is working. Why no one else does you're roof method I don't know!!!
No it can take a long time for structural problems to develop. We see it with Cavity wall insulation blocking off sub floor vents and people's suspended floors collapsing 5-10 years later. Poorly ventilated COLD timber will attract dry rot. In the case of a garden room it's far less likely to be a problem but it COULD reduce the life of the roof if done incorrectly so if you are building for decades rather than years then there is a reason for the guidance.
Makes me laugh when people state its OK to go over no one will notice . Really try and sell the property and wait to you get a survey done. Love your builds and my kitchen extension is a hybrid roof . Was fully passed by inspection and its also a flat roof this gave us more head room as advised when designed due to pitch would loose head height . Some people claim to know it all but haven't got a scooby doo .. great vids keep em coming.
Exactly, hybrid roofs work, you’ve gotta stick to the rules, on one of our current jobs the council are coming out to measure, her words to me” if your sure your under 2.5, your safe!” 🤣
I love your vids mate. Gonna build my summer house next year and will be using your vids to help. Definitely gonna finish in cedar, they look the nuts. Have you ever done one on a base of bricks? I only ask as I have a solid concrete slab at the bottom of my garden that I’m building off and I thought of doing it that way to stop water settling on the slab.
If your happy with the strength of the slab , build off it mate, two choices, overhang your structure so no water gets on the pad Or sit your build off it, sit it on dpc and galvanized uni strut
william griffin thanks for the reply mate. Didn’t think of Uni, I can get a ton of it from work. I’ll look in to that. Keep the vids coming, quality stuff. 👌
Thanks for this. I'm about to build a garden room studio with resilient bars for soundproofing and have changed the roof design to hybrid as your video suggests. As it's a soundproof room I want to use 100mm rwa45 in the ceiling and floor plus 25mm PIR behind it like you do in the walls in your other video. As long as I put foam in the gaps around the PIR and then hold the rwa45 tight up to the PIR, will this still be ok? Especially in the roof. I'm using 8x2 joists in the roof so I'll have 70mm height above the plasterboard too. Thanks in advanced! Really learnt loads from your videos!
I'm a fan of you and this channel and please don't take this the wrong way, however i'm afraid you may well be heading for trouble with this roof design. I'm only mentioning this because I wouldn't want you to make yourself a big problem for the future. My mate built exactly the same design roof for his woodworking workshop (low moisture) and after 4 years has serious issues with rot at the highest points of the flat roof. Like you, he had pushed the insulation up to the wooden boarding and not allowed any ventilation. The 9in rafters have been eaten away by 50% in 4 years by the rot! I know your rooms are low occupancy with no water so should generate less moisture, but the one you're doing at the moment is for a gym, so serious amounts of sweat and moisture, especially if no extractor fans. My mate is now having to make major changes to rescue his new roof, with replacement rafters, cutting air vents (cross & up/down) and free flowing vents top & bottom. Take care mate
With this amount of explaining it just goes to show how passionate you are with your company and workmanship, keep going an ignore the haters, beautiful sheds🤯👍👍
for those people interested in the hybrid roof discussion there are 3 key potential issues:
1. Difficulty of creating a 100% full vapour control layer on the warm side.
2. Thermal bridging
3. Hybrid designs are untested by the insulation manufacturers, so architects / surveyors / building inspectors don't like them and don't specify them.
However, in the context of a garden office, the construction on this video is, in my opinion a perfectly valid compromise. Yes there will be a bit of thermal bridging, but is that likely to cause condensation issues? Timber is a reasonable insulator so the chance of the inside face of the joists being below the dew point is pretty rare.
The somewhat bigger potential issue interstitial condensation due to vapour getting to the underside of the OSB - Ideally foil tape should be stuck on around each joist and covering a bit of the celetex - that creates a vapour barrier.
To be honest, on house extensions there is far more risk where a cold roof has been specified and the roof is not adequately ventilated (or downlighters penetrate through the insulation to the cold space. In these situations a hybrid roof with say 100mm in between and 50mm cover would be a far better option.
I think this Oakwood garden rooms channel is fantastic, some great ideas and I bet the customers are very very happy.
I used to manufacture and install top end hardwood orangeries, so much of this construction is familiar.
When I seen this notification pop up I initially rolled my eyes , here we go again I thought 🙄
But having read this unbiased comment I’ve gotta say, this is constructive and well written. Thank you for your input and I will definitely be using the foil tape going forward.
I appreciate it’s not perfect but I’m these situations it works.
Thank you for your input 👌
@@thegardenroomguru many thanks for your reply, having read through all the comments about this video you posted, I thought I'd add my 2pence worth which hopefully provides some balance.
I can see from your videos you have clearly honed your construction methods and details to produce a great product for efficient commercial production and it's very generous of you to share.
There was documents from LABC maybe 10 years ago that had some variants of a hybrid roof that had insulation between, pushed to the top, then ABOVE the joists. Thinner than a warm deck, doesn't need venting, but I agree not one other architect I met wanted to work with it - insurance purposes.
@@cd0u50c9 yeah the problem wit hybrid roofs is that it is impossible to provide robust detailing for VCL
I’ve heard you make a point about people trolling and leaving abrasive comments about your clips. All I got is admiration and thanks for you taking the time to do these videos and to educated people like me a bit. So thank you and carry on. Cheers. W
I’m not a builder, joiner or anything to do with the construction industry but I love your bluntness, well you are Yorkshire, your efficiency of working and the finished product. Keep on keeping on !
Hi Liam
I’m a general builder and have used your system and I can assure others that it does work, no issues ever in the many buildings I’ve done in the south west. Keep up the good work.
Mirroring other comments, ignore the haters, leave them to dwell in thier pits of misery. Your vids are informative, concise and occasionally funny. They break the monotony of other posters formats and I for one look forward to them. So a big 👍 for cracking builds and videos.
Love this
Completely get it. Haters will hate. Ignore the trolls. You've said it enough now if they still talk shit then they obviously can't be bothered to look at your videos explaining why you do it that way. They just want to get a reaction. Plenty of us really appreciate you taking the time to upload your work
I'm in the early stages of a garden room build right now (almost cleared the ground, but have a bunch of materials ready to go).
"tradies" have been telling me to vent my cold roof and the additional costs are ridiculous, not to mention the fact I'd need to lose internal head hight.
Thank you for this video, and for all your videos. They've been a great source of inspiration and information for me as I've been planning and designing my room.
Have you considered using battens for your cold roof material to fix to that way, it's low cost and low hassle creating your ventilation.
@dlvulpes1048 I'm all done now bud, this comment was over 6 months ago. My garden room is complete all except for the external cladding. Moved in last week 😊
Thank you for sharing this. I built my garden room with 90mm rafters to keep under the height limit and watching how you guys do the insulation has given me confidence to do the same in my build. I have first fix electrics coming this week so will be able to get insulation and membrane installed next week in time for the weather getting crap.
is your ceiling sagging if you used 90mm rafters? Using the span tables 90mm on 400 centres gets you a span of less than 2 meters? What are the dimensions of your room?
@@dugbert9 My ceiling rafters are C24 90x50 and are spanning a little over 2m wall to wall. They are certainly on closer than 400 centres and absolutely solid so far but that's to be expected as the roof was engineered and I just followed the diagrams I had been given.
Used this system on a flat roof garden room with 8 x 3 joist put and angle fillet on top of the joist to give the roof some fall for the water, full filled with 200mm insulation ,vapor barrier and foil backed plasterboard. Was so worried about moisture after 8 years took a piece out to have a look and was as dry as a bone.
Did you leave a gap between the pir board and plasterboard?
@@mylesgoward5954 because of the angle of the fillet there was a gap at one end between the plasterboard and the celotex , about 25mm
This is the info we need. Real time usage. Thank you 🙏
The one problem that hasn’t been highlighted is interstitial condensation. Using the hybrid solution shown in the video will move the dew point below the decking and even with a vapour barrier correctly installed sweating below the decking will occur. It is also worth noting that vapour barriers, even if installed correctly, are only effective below 60%RH. The guy is pretty knowledgable and his builds and videos are very helpful. However, this roof make up wouldn’t work and 50mm ventilation space would have to be incorporated to prevent future issues.
I’m not sure I agree. I’ve not found any tests performed that show sweating would occur.
Cold roofs require a flow of ventilation and that is so often compromised, I would argue a hybrid roof will perform better.
Either way, it comes down to attention to detail more than the choice of warm or cold
@@notch7139 we’ve already been back to several years after built, and no issues at all
I think you are both right!
There will be condensation, but, it is pressure treated lumber and it will eventually drip or evaporate away. If you look at what they do in America, it is very similar to this and they build everything out of wood.
On another note, you could leave that 20mm ventilation over the cellotex or put 70 or 80mm insulation.
The amount if insulation required now is just ridiculous! The difference between a U-value of 0.22 (100mm PIR) and 0.32 (70mm PIR) is 37W for a 20m2 roof with 20 degrees temperature difference. A human existing / resting produces 100w of heat.
🏆 Happy to hear it explained so plainly and couldn't agree more on other people's designs which seem to magically come under 2.5m despite 8x2s rafters! I've been going mad trying to work out my heights but this certainly helps knowing I can do away with the cold roof ventilation gap and so get my services in easily.
Do you ever have roof lights/sky lights in your buildings and anything to be aware of? I would love to have one on my little 3x3.5m studio but feel like there will just be issues with moisture, perhaps as there will be little space between cold rooftop and warm air near the glazing where the trimmers will be
Glad to hear you tell folks about the 2.5m permitted dev taken from the highest point on top of slope. Makes sense when building on a slope. Finally got out of the ground tonight so base joists & hangers tomorrow! Great update bud
Cut into the slope and get more height to play with. I've got a 400mm fall where I'm planning to build so as understand it I can drop my base level and still measure the 2.5 from the heighest original ground level, so getting more like 2.9m.
@@jmccoy555 that’s what I did mate - dug down similar amount and now will be able to frame in 2.2m doors and 6x2 roof timbers.
@@jmccoy555 - If you do dig down, put some measures in place to cope with the 1 freak day of heavy rain in a 1000 days - the last thing you want is to get them floor joists soaked or even worse end up sitting in mud after a few years...
Also - I recon a pinickety inspector would take the level at which you have dug down to build upon to be the ground level from which they will measure..
I would only cut in if you are doing so to reduce the extent of which the lowest ground level threaded bars are protruding from the ground level...
The head height in Liam's builds is fine, why push it to gain a few cm and run the risk of being forced to pull it down after a few weeks, months or years...
@@TheStumpy3496 it slopes 3 ways, 400mm across the diagonal and 200/300 on the corners and continues to fall in all directions so no chance of a mud bath. Got to drop something or the front door will be in the air!!
The regs quite clearly say its all measured from original ground level. It's actually quite a well documented loophole.
www.google.co.uk/url?sa=t&source=web&rct=j&url=publicaccess.wokingham.gov.uk/AniteIM.WebSearch/(S(lkgvbv45pljxp545tp4dim45))/Download.aspx%3FID%3D92803&ved=2ahUKEwiioeTngeLrAhUDiFwKHbUhDUUQFjAPegQICBAB&usg=AOvVaw23YIP0ATx5nNXr52iGuNpK
@@jmccoy555 Dig for victory.....
Great explanation, I bet 90% of people that moan about your roofs have never even layed one,I done a flatroof on the main scientology building in East grinstead and that was a hybridu because it was south facing they speced the roof with 8 inch of insulation above deck but with that amount we would be upto the gutter on the adjoining roof,
So I put to them 4 inches above and 4 inches in between and that's what we went for,
It also cut the fixing bill by about 70%,you do a great job your a bit swift for me but I love watching your vids
was that signed off by LA?
Blimey Liam, the dreaded AJ. I like the hi-bred roof myself or it has to go through planning to raise the roof. I am a general carpenter/joiner. As I have only done four of these garden rooms, I hang on to every word that you have said and It’s served me well many thanks.
Well done! You have described that perfectly. Anyone who is in the trade will understand you. People spend too much time looking at specs and varying ‘recommendations’ from Internet forums etc. Listen to the tradesman that do this day in day out and have years of experience not keyboard warriors. Great work chap. P.s don’t pander.
Aye, ignore the haters. I really appreciate that you've gone the extra mile at least three times now, explaining how you do the roof, and why. Keep the vids coming, you're doing great stuff.
It might work for this level of building but it will defo condensate for two reasons, first you have cut the insulation in the zone for the lights therefore a difference in temperature especially over night. Also the joists are in direct contact with the cold and not isolated/insulated. Timber is no longer calculated at zero as they do conduct, even if only slightly. Therefore the ambient air zone is compromised and condensation will pool on the back of vapour barrier. It is important to provide people with rounded knowledge, but get this is only a garden room. I have built many passivehaus timber frame homes so have maybe more understanding than most in this area. Hope this input helps someone
I would agree - the vapour barrier is cut which will allow moisture to penetrate. I would have thought the ideal would be 70mm of insulation as he has tight to the OSB - ideally glue foamed to the OSB. Then a 50mm air gap, then 38mm of insulation backed plasterboard on the ceiling joists. Not sure the vapour barrier adds much in this case as you would be cutting through it anyway for multiple spots. The 50mm air gap could be vented both ends which is ideal. Thoughts? Yes you lose 26mm head height but worth it.
On the floor, you don’t need an air gap if you have a membrane. So membrane, then 50mm insulation is sufficient, then ply, then your floor covering of choice.
I just wanted to check before I do mine… so any reactions would be great.
@@glassdomedesign if you ventilate in-between the 70mm PIR and 38mm back plasterboard then the 70mm loses its insulation value. The 70mm would need to be to the lower side of the rafter against the 38mm and then to ventilate in the 50mm gap above.
Spot on. As a fellow Yorkshire man I appreciate your bluntness.
Thanks for that mate VERY helpful. I know nothing about building anything but got a lot of common sense and the way you explain stuff makes perfect sense to me. Good on yer.
Well said Liam, “there’s more than one way to skin a cat” great job and great quality workmanship. Dave
David Robin been saying this for ages, definitely two ways to skin a cat, some people are just black and white 🙈
excellent videos thank you
i may or may not have made a mistake in my floor design, time will tell i guess
i used a steel base from uroof ltd
bonded with ct1 and screwed galvanised steel seets to the bottom and sealed all holes and sat the whole thing on ground screws, bolted and screwed each section together
filled with recycled plastic insulation, then run 25mm steel box box sections along the floor panels at 400ish centres in the opposite direction to steel floor joins, 25mm pir between, covered in joint tape, then a dpm over the lot and wrapped down over the outside of the steel , then 18mm ply for the floor
Ignore the idiots. I enjoy learning from yourself and the team. Thanks!
As usual, makes sense to me. For all the haters, they could always add foil wrap into the squares you cut out the lights then seal to the surrounding insulation. If you foil tape where the lights come through the vapour barrier that would solve their moisture egress issue too?!
Keep up the good work, loving the tutorials 👍👍👍
Great videos and your customers must love your workmanship. Great buildings chaps. 👍👍
Excellent explanation. Ive literally just finished my roof timbers and chose this system just to get the extra head room inside, as a warm roof just robs you of height. Well done great vid.
This guy is brilliant, knows his stuff and is a very good tradesman. Really enjoying the videos 💪💪
Everyones an expert in the building industry!! And on that note, a better way of doing the hybrid roof system would be to wrap the moisture barrier round each joist void so it’s sandwiched between the insulation and the ply. Also that way you won’t need to cut a hole in it when you put your led lights in. 😂😂😂
The moisture comes from inside the building so having the barrier above the insulation is a bit pointless, yes/no?
I completely agree, well said. Keep up the fantastic work. I can’t wait for the next tutorial.
So, why not put the insulation lower down in the joists leaving a (small) gap between the insulation and the underside of the roof that can then be ventilated. Is that an approach that would provide some protection against condensation ..?
Hands down...if I could afford one this is the only guy I would trust to build a garden building for me!! And as I can’t afford you I’m taking every tip I can from the channel and building my own!lol😊👍🏼 really appreciate you taking the time to show us how it’s done properly mate
Another Very informative video.
Can't understand the haters your jobs are top quality 👌
Great work Liam very good stuff keep the videos coming 👍🇬🇧
Totally agree mate as long as its low occupancy there will be no problems with condesation....its not like people are showering bathing or cooking in these rooms at most they sit in them and get drunk and watch tv ...well explained 👍🏼
Don't worry William as there are haters everywhere but professionals like you are not so easy to find.People should take a leaf out of your book and get on the tools to see how easy it is (or is not) . I spent 14 years in the wines and spirits industry and was forced out of my job due to Covid.
DIY was my passion so i have picked the tools and put them to work.There are jobs are out there if people can be bothered to work instead of trolling those who do...keep up the good work!!!!
Nick, I see you often in the comments, thank you for your support and always your advice and kind words, it’s friends, and I say friends, because of see you all as friends, tgat I keep posting 🙌
@@thegardenroomguru genuinely that means a lot William.Keep up the great work and the amazing Vids
Nick Demetriades just read back my English 🤦🏻♂️seriously, I’ve built a community and following from nothing in a small period of time. I’ve a passion for what I do, I thought I was alone. Then you guys appeared! I’m blown away, I’ll hit 20k subs next month, channel 4 and 5, have emailed me. It’s amazing and quite frankly I’m still in awe!! If you ever need anything answering just ask and if I don’t reply, call me 💪thank you, and any of you reading this that folllow me xxx
@@thegardenroomguru Don't worry about the English mate..cant believe that you have so many followers and yet you can tell from the quality of info its a no brainerAbsolutely no surprise about C4&5 wish you all the best with that and i know you will smash it
@@thegardenroomguru If you are ever in London would be happy to buy you a drink to say thank you !!!!!!!
If the insulation is 1mm out then there is a condensation hence black spots that's why the bigger the air gap above the insulation the less chance of air settling 🔨
Well explained simple no fuss can’t be more clearer than that well done mate👍
Great video as always! Thank you. I’m building one right now based on your videos. Keep it up and ignore the trolls.
Hi Liam, I fully agree the hybrid roof in this use case is the best option. I think councils should be updating the planning restrictions of 2.5m. If they increased this even to 2.65, it would allow for a warm roof. This would be environmentally friendly as it would reduce long term roof replacements, although in the sort term I can see it having a negative environmental effect due to the increased materials required, but does seem that 2.5m is an arbitrary value with little consideration as to it's impact on the design of a building.
Always interesting and learning alot, great of you to share your knowledge and methods. I plan to build one myself in the future and without your vids I wouldn't even entertain the idea. Big up Geez 😊
If you use foil back plasterboard and seal the back edge of the joints with Cilicone they act as a vapour barrier, that’s how I do mine. I also do my roof to your method since seeing your videos and it works great. I’ve never looked back. 👍
Never look back mate, it’s full of old school haters 🙌, thanks for your support and input, googling cilocone now!!💪
Good for my model railway shed which I have to reroof owing to water ingress 😮 thanks for the info 😊
Love this video, fantastically explained .. I’ll certainly be doing it your way as I’m 6ft 7 😂👍🏻
What your doing is really smart to stay within the hight limits personally I wouldn't bother with the vapor barrier on the inside if your gona cut holes in it for sockets downlights etc . Iv built a few houses and used blower prof on the outside osb and tape the joint s
Fewer penatations . Your garden room s look great
Thanks for explaining this as I wanted know how to insulate my shed and was worried about venting the roof
Got so many hybrid roof haters , but it works done right
Using your hybrid technique on my garden room right now and saw the report I think in a later video. Great info and keep 'em coming ;-)
What’s the moisture barrier for if you’re cutting huge holes in it for a spotlights!? You can’t use spotlights in a cold roof because you break the moisture barrier
Can't thank you enough for sharing all your hard work and info with us DIY guys. It's such a valuable resource and you make it look so easy. Cheers 👍👍
I came across this video as I'm researching how to deal with unvented cold roof. I'm building a summerhouse and am up against the height limit as you describe. I'm of the same view as you; low occupancy and in my case, as one wall will be a bifold door and probably open when occupied, there will be very little warm moist air in the room anyway. Most of the advice on domestic construction is aimed at occupied dwellings and designers have to work on worst case of family taking lots of showers, cooking, drying clothing so high moisture levels. I've also come across research from Germany that backs up the cold roof but with no cold air void (as your build) although this requires attention to detail and ensuring no air can flow form inside through the roof deck. The German research also criticises the assumption that air flow in a vented gap will actually remove the trapped water; if there's insufficient air flow then all you've left is an uninsulated air void for cold moist air to condense on the timber. In my case I'll be fully packing the void, VCL and also using a spray applied sealant on the underside of roof deck at any possible air gaps. German research also recommends using a smart VCL (which can change permeability and allow any moisture trapped in the roof to vent down into the space in correct conditions) but it cost more than a standard VCL so I'm not using it but I am installing a MVHR with humidistat to deal with the odd occasion when the room may be used with doors closed and a few persons in it. I'm a professional in the construction industry (Site Engineer with Construction Degree and over 25 years of experience) and yes, a warm roof would always be a best option but sometimes it not possible. My thought are if the roof structure has no air leaks then how can moisture vapour (which can only be airborne) get into the cold roof space in the first place?
Hi Andrew
Not sure if you have seen a later video where I talk about the report a viewer did on the hybrid roof we do. It states that there is no risk of mould build up snd any moisture that does occur will dissipate in the summer months. It concludes the hybrid roof we do will not fail under the conditions we install 👌
Really good, and to the point explanation of warm roof/ cold roof/ hybrids
I don't understand weird people. I've learnt a lot from your videos. Thanks
Just doing insulation in my workshop / gym and was wondering about this, thanks for the explanation.
Good man, you have to put up a bit of a fight to get your point across sometimes.
Ive had people privately message me to troll me about this one 😂
As far as I know, you are not meant to cut the vapour barrier around the lights as you're defeating the purpose of it? In fact, Roger from Skill Builder mentioned this in one of his videos? Can you please explain?
Hi I agree with your idea. All this warm roof cold roof stuff. It all so OTT to me. So you have to air vent between the joist. So in December when it’s freezing cold isn’t that air gap going to get cold and thus making the ceiling cold? Hasn’t nobody thought about that?
Can’t wait for the full tutorial Will on the next one 👍🏻. Really enjoying the videos.
A would like to see a revisit few years down the line to visually see what roof is like behind insulation the rubber roof itself gets warm in hot days, it doesnt matter about low amount of people in it the venting to the underside of ply is to cool the rubber or felt on hot days by blocking off eves your goin to make it condensate behind insulation just my opinion of course i also am a builder and roofing contractor for 25 years
I hear what your saying , sips panels ?
They have no vent,
@@thegardenroomguru anywhere you have no foil tape on is somwhere hot and cold ambient temp can mix and escape ,wasnt judging meerly sharing knowledge from jobs we have been called to remedy and sort
Im still not sure how to do my shed ceiling. Lots of conflicting information. It seems that people in the UK at least, are convinced it will rot and fall apart if i dont cover the eaves in 50mm vents, because enough warm air will leak past insulation, tape, sheets, and foam. But the air flow through a small gap between timbers somehow wont disperse the torrent of wet air coming up from my mostly unheated shed. Maybe people are just overcomplicating things
Brilliant. Clear and perfectly explained.
Good vid. Clearly you know what you're doing. Well done.
Thanks for showing people how to do these jobs.
Thanks for the videos...they're really useful. Very clear.
Now, I get that the air below the insulation is ambient temp so no condensation, which makes me wonder..
do you really need a moisture barrier? (Especially in a low occupancy room eg home office) I'm not saying you don't. I'm just wondering why.
Love watching his videos make amazing rooms
Hi there I’ve just built a single skin brick shed/bar. The building up rubber roof on and doors/ windows in. When it’s cold there was loads of condensation on the obs roof in the morning and I’m wanting to know what’s the best solution to stop this. The hybrid roof tour on about or adding air bricks to my brickwork. I wasn’t planning on plastering boarding it or anything like that just paint the inside
Thanks again for sharing your valuable knowledge top job as always
Just discovered your channel & couldn't subcribe fast enough! What a well built room! Wish we built this way in Australia. Interested in a working holiday?
Enjoyed the video, and your clarity of thinking & whiteboard illustrations are easy to follow. One question though: I follow your thinking re the ambient temperature air gap above the ceiling but below the insulation, but why not completly fill with Foam insulation leaving no air gap - no air, no moisture vapour to condense out? What am I missing?
Nothing mate, 100mm enough to insulate the room, the rest is an overspend
Why have any air gap at all? Serious question. Does it help insulation? I used a foil based membrane, so I guess it would be defeated by contact, as far a radiative resistance is concerned.
Great vid, Is this is why you can successfully frame and spray foam a shipping container with air gap on inside at ambient temp, then moisture barrier and ply or Osb with no sweating issues?
Thanks for demonstrating this and your excellent videos - they have helped with my build! I am going to use this approach but use the 20mm space above the insulation instead. There would then be a further added benefit if this slim area could be ventilated... right?
20mm space above the insulation is no good. But if you've got to do it then yes it needs venting
Best videos on UA-cam
For a roof to qualify as a hybrid cold/warm roof it needs to share characteristics with both - otherwise it's not hybrid. The defining characteristics of a warm roof is that the air/vapour barrier and the insulation is placed above the joists and the air/vapour barrier isn't broken by lights or other penetrations. Your roof place all the insulation below the sheeting (between the joists) and the air/vapour barrier below the joists. This is the defining characteristics of a cold roof. A cold roof does not have to have an air gab to be a cold roof but if you don't want to get into trouble you need to vent the bottom of the sheeting and this is where the air gab comes into play. If your construction was safe then every cold roof would be done that way - and they aren't. More over the air gab below the insulation doesn't serve a purpose. Filling it with insulation would make for a better insulated roof and would be a better option. But your construction is missing the venting of the sheeting and is therefore an unsafe construction. For it to be a hybrid cold/warm roof you would need to place a big part of the insulation above the joists. In my climate zone I would think that having 2/3 of the insulation above the joists and air/vapour barrier would be OK and you could place the rest below. I don't know what ratio would work in you climate zone.
Hope this helps...
Agree completely. You can't assume that no moisture will penetrate the moisture barrier and so must vent above with this design. What we seem to have here is simply an unvented cold roof similar to those often found on other youtube videos where rot has formed. Seems like quite a risk just to avoid a pretty simple planning application.
Watch the video that I upload tonight, showing a roof 3.5 years after it was built, no mould whatsoever
@@thegardenroomguru That's interesting. I'm not doubting that this design can work, and I do take your point that this is the ultimate aim so who cares. But I am something of a pedant with this stuff having tried to alleviate condensation issues in my victorian terraced house, and at least on paper, something doesn't quite feel right with your design. On the other hand, I agree with a point you made in another vid on SIPs, although I suspect the key difference there is air-tightness within the SIP. I fully appreciate the effort you're going to and think the vids are great, but I remain sceptical that this design would withstand a high-occupancy rate / cold winter combo. Would be very interested to see some temperature measurements from within the fabric... told you I was a pedant ;)
Totally get you, I do state that these are low occupancy rooms and if we do an annexe for example where living accommodation and bathroom are included then we would use a warm roof as of course planning would of been applied for so overall height would be not an issue as it is with these rooms
@@thegardenroomguru That you build unvented cold roofs doesn't mean that all of them will have mould or other moisture related issues after a few years and that one of your unvented cold roofs doesn't show mould or other moisture related issues after a few years doesn't mean that none of them will after say 10 years...
Your likely to get cold bridging through the joists.
And issues where you reduce the insulation thickness for you lights etc.
Although in principle I have no issue with your proposal. 25mm continuous insulation over the rafters, then plywood would be better.
Reality is dormers were made like this for years with very few issues.
The vapour barrier is the critical item.
Thats exactly how we make them. Great work.
Hi, great channel and great content. I have a question that no one can seem to answer. The bottom of my garden has steps leading down to a lower section (I believe the retaining wall is around 3ft high). I would like to build a garden building in this space. So do the height restrictions apply from the ground of this section or from the ground of my main garden?
The biggest issue I have is the fitting of down lights introduces holes in the construction with very little insulation above them. I'm not qualified and not in the trade. Built my own warm roof and sacrificed a couple of inches headroom.
Good stuff all under control..... top spec product 👍
You don't mention "dew point". Where have you calculated the dew point to be?
Bloody great video. Even numpties like me can follow it. Just doing this in my roof of my garden room at the moment. Can I assume it is the same principle for the walls? I've got cladding, then breather. So the insulation board would sit up against these two layers. Cheers from Sunny Devon!
👌this is how I built mine. Only prob I seem to be having is a slight bit of condensation on my laminate floor in the corner at the skirting board I think it's due to ventilation i have a oil filled radiator and 2 x 4" vents I'm not sure if this is enough its 3x3 garden room
It’s an issue at this time of year due to levels of insulation and moisture held in warm air, soon as it meets a cold area it condensates. A dehumidifier will work wonders mate
@@thegardenroomguru I have just bought a 300ml dehumidifier and its collecting moisture. Do you think I need more vents or will 2 be enough. Love your work by the way 👍
It’s two more than we put in mate, we gave trickle vents on the glazing units, it will always collect water mate, it would if you put it in your living room, it’s just in the air, becomes apparent at this time of year
@@thegardenroomguru that answers my questions thank you mate 😉
hi Liam - regarding span..you are using a 120mm joist in this example. Looking at the span tables that would give a max span of just under 3 meters. So I assume the bigger the garden room, the taller the joist and therefore the threat of running foul of the max height of 2.5. Are the span tables over egging the pudding for a garden room? I ask because I am worried about my ceiling sagging as I am under spec against the tables. I have fitted a warm roof as the building is inside a big agri building itself and it's farily lightweight as I have topped it with a tarp, not felt or rubber. Am I worrying too much??
I'm building a basic garden shed and I'd like to connect the roof vapor barrier with the wall vapor barrier. I'm leaning towards the hybrid solution because then it's very easy to connect both. Most people recommend a warm roof but then it's a lot of work to add vapor barrier strips between the joists. Do you know a simple way to do this?
If I would opt for the hybrid solution. The space between the IPS insulation and is there a max/min height I should take into account?
have a look at monopoly framing.
Great video, could i use Rockwool type batts instead of the rigid boards you have used. I understand they will be lower insulation values but Im thinking from the condensation point of view cheers
I have a fiberglass flat roof with 2 roof lanterns and would like to know if I can use breathable vapour membrane between the insulation and plasterboard to prevent condensation....its a brick building. Thank you
Excellent concise well explained video.. many thanks
Hi William, Great video once again. Please could you advise what you would do for the roof if you were putting a hot tub in there with half height walls on the front and sides? I am not planning to plaster or anything and wondering what to use for the ceiling? Regards, Simon
A big problem with all insulation calculations is how the insulations manufacturers have the energy loss calculated. If you put reflective insulation directly on a hot plate then that insulation will absorb heat more than if it was given an air gap in front of it. This in itself will change how ambient temperatures in front of the insulation or behind plasterboard are. When you ask Celotex about service voids compared to for insulated plasterboard that overall has the same thickness of insulation, they will tell you that it is the same. Which is not true.
Your the man,,,,
Nice video, straight up no BS , i like that.
A neighbour did this option 3 years ago, they've just had it ripped off because of the damage the moisture has caused. That being said I'm slightly tempted to try your method but wondering how long you've been doing it this way? If it's fairly recent then I'm slightly concerned
The system you described is exactly how SIPS panels work. Got to ask though, why add the moisture barrier before the plasterboard?
Hi William ... All cold deck info tends to be based around habitable areas. Thanks for clarifying the use of cold deck for garden rooms and confirming what my father in law constantly says about limited condensation risk. Can I ask about heating and with an under insulated raft slab, would you suggest underfloor electric heating or convectors or both? ... Used for office working 5 days a week, size is 12m2 with bifold doors
Well explained mate,always informative and you clearly know what you’re doing. I’m looking at building a woodworking workshop in my garden to replace my old garage,and looking at 30 square meters floor space and using every available and legal height dimensions I can,but I’m lead to believe I’ve got to have the new build at least 2 meters from from a boundary,it’s doable but leaves a load of empty space around it. Do you provide a design service? I’m based in north Manchester . Keep up the great videos,onwards and upwards.👍
This roof is fine because the due point is going to be located in the middle of the 100mm insulation where there is no room around it for air to condense, there theoretically could be a tiny amount of condensation around the due point location in the insulation if it isn't cut tight, but hardly worth worrying about. A better solution might be to fill the cavity completely with spray foam insulation which would completely remove the possibility of humid air buildup.
Exactly mate if you had any issues with your methods like moisture or condensation issues, they would show up within a few months. The fact they haven't and you're not being called back to jobs and your channel is growing means what you're doing is working. Why no one else does you're roof method I don't know!!!
@@macsmith6216 you wouldn't need to. Plasterboard would show ANY moisture as soon as it develops. I take it you have a problem with this method?
No it can take a long time for structural problems to develop. We see it with Cavity wall insulation blocking off sub floor vents and people's suspended floors collapsing 5-10 years later. Poorly ventilated COLD timber will attract dry rot. In the case of a garden room it's far less likely to be a problem but it COULD reduce the life of the roof if done incorrectly so if you are building for decades rather than years then there is a reason for the guidance.
Makes sense to me. Are care and stay safe.
Makes me laugh when people state its OK to go over no one will notice . Really try and sell the property and wait to you get a survey done. Love your builds and my kitchen extension is a hybrid roof . Was fully passed by inspection and its also a flat roof this gave us more head room as advised when designed due to pitch would loose head height . Some people claim to know it all but haven't got a scooby doo .. great vids keep em coming.
Exactly, hybrid roofs work, you’ve gotta stick to the rules, on one of our current jobs the council are coming out to measure, her words to me” if your sure your under 2.5, your safe!” 🤣
I love your vids mate. Gonna build my summer house next year and will be using your vids to help. Definitely gonna finish in cedar, they look the nuts. Have you ever done one on a base of bricks? I only ask as I have a solid concrete slab at the bottom of my garden that I’m building off and I thought of doing it that way to stop water settling on the slab.
If your happy with the strength of the slab , build off it mate, two choices, overhang your structure so no water gets on the pad
Or sit your build off it, sit it on dpc and galvanized uni strut
william griffin thanks for the reply mate. Didn’t think of Uni, I can get a ton of it from work. I’ll look in to that. Keep the vids coming, quality stuff. 👌
I was woundering if i can do simular think and you give me the answer. Thx.
Thanks for this. I'm about to build a garden room studio with resilient bars for soundproofing and have changed the roof design to hybrid as your video suggests. As it's a soundproof room I want to use 100mm rwa45 in the ceiling and floor plus 25mm PIR behind it like you do in the walls in your other video. As long as I put foam in the gaps around the PIR and then hold the rwa45 tight up to the PIR, will this still be ok? Especially in the roof. I'm using 8x2 joists in the roof so I'll have 70mm height above the plasterboard too. Thanks in advanced! Really learnt loads from your videos!
I’m doing similar to you. Did you go with they hybrid and how is it performing in this damp weather?
@@royfoster7010 yep performing very well. vapour barrier on and plasterboard half of it, no damp or condensation
DW Studios Guitar, Bass and Drum Tuition, Repairs & Setups, Recording Studio
Awesome! Have you got an air gap cavity to help with sound proofing?
You know you’ve made it when you get your own troll. 🤣 Nice work buddy 👍🏼 really good content
I'm a fan of you and this channel and please don't take this the wrong way, however i'm afraid you may well be heading for trouble with this roof design. I'm only mentioning this because I wouldn't want you to make yourself a big problem for the future. My mate built exactly the same design roof for his woodworking workshop (low moisture) and after 4 years has serious issues with rot at the highest points of the flat roof. Like you, he had pushed the insulation up to the wooden boarding and not allowed any ventilation. The 9in rafters have been eaten away by 50% in 4 years by the rot! I know your rooms are low occupancy with no water so should generate less moisture, but the one you're doing at the moment is for a gym, so serious amounts of sweat and moisture, especially if no extractor fans. My mate is now having to make major changes to rescue his new roof, with replacement rafters, cutting air vents (cross & up/down) and free flowing vents top & bottom.
Take care mate