I put a flat roof on my extention 20 years ago, followed your instructions to the letter , a fantastic system, the only thing different that I did was to put gutter seal on top of the kerb before putting the osb on to give an extra seal at the joint between the kerb and the osb just incase there was an air gap between the two . No leaks to date and looks as good as the day it was done , I used torch down felt , . Thanks Steve for all of your advise 👍
It's all about learning how to learn this is what they don't teach you at school personally I never went to school but I didn't realise I was always trying to learn and I'm still trying to do that now.
@@SteveRoofer Learning how to learn is a problem I had all my life. I am 62 and was in my 50s before I realised this was my main problem. It could have saved me so much time if someone had recognised this instead of just telling me I lacked confidence. I’m not stupid, I have a Mensa test result of 133 IQ. Well, better finding out now instead of never knowing. 😂
I always enjoy sitting down and watching a Steve nerd waffle in a subject I really enjoy myself, I run my own company flat roofing operation designs in basically the same way
Thanks for the nice comments. Realistically, I actually enjoyed doing this video. Just took my time waffled on. Wish your opinion though wood on the top is one question I sort of asked and the other one is it's not so much the air vapour control layer but the way it's fitted.
I have vexed over this for weeks and had a consultation with Steve last year. The very important point Steve makes is that the most vapour controlled layer is closest to the inside of the building. If this is done then vapour within the roof construction will find its way to the outside. One way to show this is to download the Wufi programme from Fraunhofer which does a proper condensation analysis (free verison will not give you a UK weather map - I used Brussels as it is not too different). This will allow you to prove that condensation will move out of the roof construction and that no mould or condenstate will accumulate within the building or within the roof construction.
Hi Steve, I love your videos! I have installed many domestic and commercial warm roofs. I always completely agree with what you say! For me, alutrix 600 is the only VCL product to use, and using contact adesive on the wall upstands sticks like 💩 when done properly. Also, I always take the VCL up the timber kerb and finish off on the outside edge to create a better seal. I was always told that you are creating a sandwich, which I hear you say. Thanks for brillant videos, Steve.
Built my first house over 30 years ago and now on my fifth. Steve putting me on to Alutrix has been one of my biggest "finds" ever. Even more so when you're working slowly on your own. Once you know, you know and it's also a huge big up for the power of youtube for educating and informing.
Thanks Steve. I used the information in your previous warm roof videos to design the roof of my daughter's 'tiny' house. As this didn't need to comply with building regulations, we used 100mm EPS for the insulation. We used Alutrix 600 (with FG35 primer on the vertical upstand around the roof), plywood on the top and bottom of the insulation, and EPDM as the weather-proof layer. The EPS is vapour permeable (about the same as OSB). We took the Alutrix 600 over the sides and slightly down the outside face of the upstand - when primed with FG35, the Alutrix sticks incredibly well to wood.
Why didn't your daughters tiny house need Building Regulations? Any exemptions for buildings that are under 15m2 or 30m2 floor area all state the the building must not include sleeping accommodation. Even if you didn't need to comply with building regulations why would you choose to use such an inferior material as EPS? 100mm of PIR would likely have halved the energy loss through the roof (though still not enough to comply with Building Regs). The tiny additional cost would have paid for itself in no time.
@@mikebarry229 The tiny house was in the rural part of a foreign country where different exemptions applied, and small quantities of high-performance insulation were impossible to obtain. The EPS was a graphite-enhanced version with a thermal conductivity of 0.030 W/mK, so it was about 2/3rd as good as the best insulation. We were restricted on the height of the building as my daughter wanted to keep it transportable on the road network. The U value of the roof is a bit better than the walls and floor.
We do warm roofs. We use low perm barrier on walls and roof to make a shell. Then install staggered mineral wool batts and boards. To minimize thermal bridging. Osb usually has clips between it here on a roof. We use tongue and groove white cedar with our open trusses. In cold, frigid regions (climate zones 6, 7, and 8), dramatic temperature differences between the warm inside of homes and the colder outside creates an intense vapor drive from the inside to the outside. Applying a permeable air barrier on the outer side of the exterior insulation enables the vapor from the inside of the building to diffuse out. The lower the climate zone the colder it is here. Actually in zone 5-4. We do external vapor barriers. Were as Canada and some states do interior vapor barrier. We would have to vent that roof at the wall if heated. To release the warm moist air. Of course its colder here and I am also in maritime climate too. We don't do flat roofs because of snow loads. Nothing less than 4/12 pitch. And are at a 70 pounds per square foot snow load.
I'm not a roofer, just always interested. I've heard both arguments OSB/ply over the top of foil insulation or the tissue faced insulation with no topping and I believe both are credible if done correctly but I'd tend to favour the OSB/ply top in case of future walking on, etc. Thanks for sharing Steve, I hope you had a great Christmas.
I really appreciate this video Steve, super informing. Would you mind doing a video some time about how to AVCL, insulate, and EDPM detail a skylight/flat roof light? Thank you
Look forward to getting notifications on your videos. I've just spent the last two days putting on the Alutrix 600 VB on my extension's flat roof, with the FG35 primer (nothing coming apart when using the primer!). I'm going to use tissue faced insulation, with a solvent-based adhesive for an EPDM final layer, I don't like the thought of timber being right below the cold side of the warm roof...
Come the warmer months I will send you the video after I've built my garden office - it's being used as a test bed for the main house with what I learnt while working as a sparks in Texas and Cali. They're leagues ahead over there in terms in warm building/ perfect wall construction. Possibly it will be helpful to you and also good for guidance as the 2 climates I've specked it from are a lot dryer than the UK.
Brilliant information as always, thank you Steve. Had no idea foil faced celotex had poor vapour impermeability, I presume that includes the foil tape at joints?
Fantastic and very informative videos. I've discovered this channel as I want to get a garden room built. From what I can tell every company will build a cold roof and cut holes in the insulation for lighting. I assume the extra cost in materials, the extra height a warm roof adds, more time and even the ability of correctly sealing it all up is why most builders go for a cold roof instead?
I can't understand why people do these garden rooms the way they do it's a complete no-brainer to clad the outside of the building with super quilt around the walls and over the roof no-brainer think of it like this in the winter what do you do? Do you put your jumper on i.e. pull your arms through it so everything is inside and nice and warm or do you eat your jumper and put the insulation in the inside insulation on the inside? Wrap the outside of the building in insulation?
The disadvantages of a warm roof are listed in your second paragraph and they are all disadvantages for the contractor. The disadvantages of a cold roof are in your first paragraph and they are all disadvantages for you. A cold roof done the way you describe without effective vapour barriers and pockets cut for lighting will cost you dearly in extra wasted energy and premature roof replacement. Stick to your guns and find a contractor that puts your needs ahead of theirs.
As regs march on. More emphasis is being put on testing like BRoof T4. As non combustibles become the desired route. There has been huge changes to what’s being supplied on major projects. Due to this “grenfell” effect. And it is now being frowned apon to include timber within a flat roof system. I work for a major flat roof manufacturer (well the uks largest) and inspect said projects. A quality AVCL membrane is a must. And it amazes me through my inspections how many “roofers” do not apply this important layer correctly. And how many “smaller” outfits will omit it altogether.
I am applying your advices in Siberia. In extreme winter temperatures. But we can't have a flat roof here. Too much snow and so the beams are too expensive. But we can do the same with a regular roof. Just by using a standing seal metal roof over the osb.
Terrific & shows there are expert installers out there. Sadly councils like Westminster never use quality smaller suppliers, instead relying on having a small number of big contracts with Moron Swindle, who then push any specialist work including roofs to tiny hopeless subcontractors One of these tried to cut through the ring main foundation in our listed building when replacing a waterline (they claimed they didn't and then said "what's a ring main foundation") then cut through an 8' solid slab for access into a flat & filled it in with bagged rapid set cement with no reinforcing/rebar (obviously no supervisory oversight or sign off).
As a Building Surveyor and Engineer I have to confess that I have never heard of a "ring main foundation" either. If I were to guess I would assume you mean a piled foundation, as that typically includes a ring beam linking the pile caps together, or possibly a raft foundation which typically includes a toe beam around the perimeter.
@@SteveRooferGreat! I’ve loved these two videos, and learned a lot (especially about available materials). But would really appreciate something similar on really upgrading attic insulation. I’m thinking that I can apply the principles, but worry about what happens at the eaves of a stone built slate roofed cottage. Where the eaves are virtually impossible to access internally? And I want to retain some storage space for suitcases and, of course, Christmas decorations! etc. Also something that never seems to get addressed is making that space rodent proof or at least resistant. (Field mice want to move in annually around Oct/Nov)
Nice update Steve - we’ve got a utility room with a concrete flat roof that condensates badly inside - we want to put a warm roof on it but can we use the epdm that’s on there now as a vapour barrier under the new insulation as it’s in great condition still or would it be best to remove it & start again from scratch - thanks lee .
Very timely, I'm building a pitch warm roof for my extension, I have bought marine plywood for the lower deck,the 600 VCL product, tissue faced insulation, and dpm above it. I don't need an upper deck I reckon, can you confirm this point? Also, what brands of thermo broken fixings do you recommend for the counter batten/batten installation over the DPM? Thanks so much, your videos are super educational, I picked up in this one the need for a coating for the walls. Btw, a friend recommended a heat recovery extractor for the kitchen which makes lots of sense after all these efforts going into sealing the building envelope..
okay reading your details above so you're gonna use some kind of marine plywood for the lower deck that's great 600 VCL product tissue faced insulation that's good and a DPM above it? Why would you do that purpose? Do you think that is going to serve you don't need a DPM above it. Okay I get my firmly broken fixings from a company called fix fast.com. If you can't find them just give me a email and I will send you a link to them. Good luck. Speak soon send me photographs of it being constructed even you never know, I might be able to use them. Speak soon.
@@SteveRoofer I meant a breather membrane, not dpm. Thx for the fixfast tip. So in that configuration of a low pitch roof, would you keep an upper deck or just do away with it? I will send you pictures, I've got a good carpenter and a good detail in mind for fixing the counter batten to the end of the rafters. I'm just a bit uncomfortable with these fixings throughout the bm/insulation/vcl to hit the lower deck. I take it you have to have all the fixings hit the rafters underneath to minimize chances of any bridging?
@@michelleconte8428what roof covering are you having on your battens and counter battens? This is all important info. Your fixings need to go into the rafters for strength and nothing to do with thermal bridging, though it will reduce that aspect too. What purpose would a timber deck over the insulation serve? It would only increase the vapour resistance of the roof construction at a point where you want it to be breathable.
@@mikebarry229 I have low pitch interlocking clay tiles. Ok, so it sounds like we're in agreement, the upper deck is not serving any useful purpose. I thought it might from a structural standpoint, but given that no-one will walk on that roof...
@@michelleconte8428 so long as your tiles are OK for the shallow pitch you should be fine. The ply under the insulation and directly connected to the rafters should give you all the bracing and structural integrity you need, at least for the rafters. If you are using roof trusses they may need additional bracing to internal compression members.
All depends on on the roofing system you are doing. I mainly use single ply pvc. Which does not need ply board on top of the insulation. Also some single ply manufacturers don’t like you using OSB as the deck as it does not hold a screw as good as ply for screwing the membrane down.
totally agree with you and PVC is one of the better membranes out there. I always put it just a little bit above EPDM however it does come with the cost and as I'm primarily in the domestic world not everybody wants to use it and I also agree and I hope that this came over in the video that in the perfect world timber would not be used in the construction above the air vapour control layer.
@ your videos are brilliant done. I always tell my customers to watch your vids so they can understand a warm roof and cold roof, to better understand them.
Great video, and your advice is invaluable. Having the opinion of someone who has seen where things go wrong is the best guide . I am about to install my own warm roof this spring and ive watched all you videos. Its a medium sized roof, not complicated, one roofligh backing onto a new extension. Ive done a few grp roofs on the past and plenty of pitched roofs. For a competent person but not a professional flat roofer any advice on what to go for on my own home? Liquid rubber, epdm, flexible grp?
Flexible GRP is a bit of a contradiction. There's no such thing, but it's a good marketing ploy. Personally, EPDM or felt make sure that you have good falls on the roof that is the key good drainage no standing water I cannot understand people who put a minimal fall on the roof basically 25 mm in every 1000 is what is required but what the hell? Why not? Double that or quadruple? I always do if possible.
No where would you put it? But I'm really tired that you're actually getting there. Believe it or not there many many people don't understand this like I say on the video under the air control layer is internal so there's no where where to vent
Great informative video, time flew by watching it, looking forward to the ridge videos, as have that as a job on my house in the near future. P.S. the promised links aren't in the description.
This is a link to the new supplier of AVCL,s steve@stratawaterproofing.com www.stratawaterproofing.com Get back to me if you use them and tell me how you get on
@@SteveRooferI purchase classic bond epdm from this company as there based here in N Ireland aswell as there sticky back VCL I've had no problems with them apart from price. Cheaper to buy from England but then delivery cost can be expensive. They sell many different flat roof products but I've been asking for a long time to get trained on the pvc system (the name of product escapes me right now) but still waiting about 3 years now
Hi Steve great level of detail shared. Thanks.. just a question regarding using 18mm osb on top . If hitting dew point on the underside of the OSB will it not eventually cause the OSB to rot? I know you say Moisture evaporates out eventually .. I have head knauf do cement boards for warm roofs. Any views on using them instead of OSB?
Personally, I think everybody is overthinking this. All you need to do is get the air vapour control layer perfect like my example wrap it everywhere and put a top on it. It's a sealed unit with only the moisture in it locked in. It's a sealed unit. nothing can go wrong.
@@SteveRooferreal world is important here, flat roofs have been around for more than 100 years and the vast majority have been constructed as cold roofs with a timber deck. Consequently home owners and trades people generally have an expectation that they will be able to access a flat roof for maintenance purposes. At a domestic level at least I feel the risks of installing a timber deck between the roof membrane and the top of the warm roof insulation are insignificant compared to the risks of not doing s. For commercial buildings maybe less so. For the reasons you explain if a timber deck does deteriorate in this location then you have serious problems with the roof that need to be addressed regardless of whether you have a timber deck or not.
Why don’t you like glass fibre on tongue and groove osb? Movement? Cracking? I just got a job done with this spec, looks solid to me but I’m not that clued up on fibreglass.
Thanks Steve. Very informative. Your point about the ply at the end.. does this hold true on cold roofs? Can the deck go onto the joists and full fill insulation between, assuming there is a very high performing VCL? I’ve drawn this up and have firrings above the structural deck and another layer of ply with steel roof finish. There is 50mm minimum ventilated space. The structural deck is required by the engineer. I’d like to avoid ventilating between the firrings and also a 50 mm cavity under the structural deck so full fill insulation would be better.. what do you think? hope this makes senses. Thanks
The short answer is no - don’t build a cold roof. They no longer work effectively. The issue lies in the insulation placed underneath. While insulation used to allow some heat loss, which kept the cavity warmer and allowed for drying potential, today’s thicker insulation changes the thermodynamics. Without that drying potential, cold roofs stay damp for longer, increasing the risk of problems. In my opinion, cold roofs are no longer a robust construction method. If you reduce the insulation, they may function, but at the cost of significant heat loss - you can't have both
The short answer is no - don’t build a cold roof. They no longer work effectively. The issue lies in the insulation placed underneath. While insulation used to allow some heat loss, which kept the cavity warmer and allowed for drying potential, today’s thicker insulation changes the thermodynamics. Without that drying potential, cold roofs stay damp for longer, increasing the risk of problems. In my opinion, cold roofs are no longer a robust construction method. If you reduce the insulation, they may function, but at the cost of significant heat loss - you can't have both but I have some tricks up my sleeve that will be coming out very soon. I have two new ways of doing warm roofs that don't need ventilation. One of them is extremely interesting and there is a lot of data saying that this works if you give me a contact by email or you wanna phone me at sometime I'll talk to you through it but I haven't got enough information to put the video out yet so I'm keeping it up my sleeve at the moment
Hi Steve, how are you fixing down the insulation and the top layer of osb or ply ? I see allot of people winding screws through the hole build up and into the joist but I can’t see that being any good for the roof!
Hi Steve. What would you recommend for a VCL for a cold flat roof? Any recommendations for tape? Do you go bitumen tape? If you’ve already done a video like this one but for cold roofs then a link would be great.
the green one that I show on the video which I can't remember the name of is the one that you should be using, but you know it's really expensive but it's time you buy all the tapes and everything. It's a real mission. I did a example a few videos back I can't go back and look takes too much time, but it's out there and it does show the different materials. Just look up wa, sorry cold roof barriers something like that and I named them all there and I also share how to do it on a test test week that I had good luck. Send me photos and videos as and when you get them speak soon.
Hi Steve, Thanks for all the informative videos! I'm doing a lot of research since I’m planning to build my own warm roof. The plan is to mechanically fix the PIR insulation using thermally broken fixings (plastic + screw). In doing so, I’ll be screwing through the air vapour control layer. Unlike in your videos and advice, I won’t be using an Air Vapour Control Layer with a sticky back (e.g., Alutrix 600). In the Netherlands, the price of AVCLs with a sticky back is enormous. What would you suggest to keep the AVCL airtight? Should I dip the tip of the screws in glue or silicone sealant to seal the holes they make in the AVCL? The roof buildup be: 18mm Underlayment - Miofol 125AV (AVCL sd=1500) - 100mm pir isolation 2x aluminium foil facing - 20mm pir Isolation with tissue facing - EPDM. Thanks!
Good plan with the warm roof! I totally get the cost issue with Alutrix. You might want to check out SIGA Majrex® - it’s a vapour control layer that works like cactus skin to keep moisture out. Look up “compact roof” on their site and check their blog. I’ve done a couple of these and I’m gathering data for a video soon. Let me know how it goes!
you always put more around the outside edge and then, as appropriate, realistically on the inside does depend on whether you're using T+G ply or not but obviously you need to put down enough and that becomes obvious when you're doing it because it becomes really robust under foot
So you glue the insulation on the air vapour barrier? No screws anymore? In the past you had roofs failing because of moisture in the insulation ,if I am correct to remember. Thanks, Dennis
you remember correctly? I like to always use mechanically fixings however more and more now people are gluing insulation down. It's a choice scenario personally I do a bit of both these days.
No, not at all. If you get the insulation outside done correctly you don't have to put some inside. There's an interesting theory here in the winter. We always put our sweaters on. We never eat them if you eat them you're gonna get cold on the outside! Hence why always put you insulation around the outside.
Sorry but there is something I quite don't get : you advert for a 130 green vapor barrier (VB) on top of the 13mm plaster board, then a vent space, then a 18mm OSB, then a +/- 1300 VB, 150mm insulation, Plywood, then a +/- 200 VB on the very top. You argue that the top layer must have a lower SD value than the interior VB so to a oid condensation. But what about the internal green VB with a 1000+ SD VB on top of it? Acording to your logics we may get condensation at this place.... Could you please elaborate?
Don’t need expansion gap between sheets. You have to leave 25mm at the abutments only. And if you do use fibreglass lay your osb up side done so the resin flows into the gap and you will have a stronger joint
Another great video as always Steve. What was the name of that paint on adhesive to stick the barrier to the walls? I sent you an email today in regards to using battons on a cold roof example
anything that makes the wall not dusty but we use spray adhesive, which is a contact adhesive but anything like that will do as this stuff really sticks to anything.
Thanks for the informative video. I am in the process of starting an extension and would like some guidance/advice. Please let me know a suitable time to contact you. Thanks Rizwan
Keep adding to insulation thickness and it's becoming, or already is diminishing returns. Who is ever going to notice the difference between 120 and 150mm of insulation, when the room below, itself needs ventilation to be healthy. Plus people are knocking out entire lower elevations to be replaced with huge bifold doors, the wall insulation going in the skip!
How would you make a warm roof suitable that you can place decking over the top without it sinking into the soft insulation or if you want to put solar panels over the top waited down? How would you transfer that weight?
They're using glass faced gypsum as a coverboard in the US. No organic material, no mold. With smart membranes you can use mineral wool to avoid using petrochemicals, which will be popular for some clients, and it allows for any moisture on the membrane to dry inwards on warmer days. Asiri Designs does an excellent series on the building physics: ua-cam.com/video/-6y2ooXxqfU/v-deo.htmlsi=ZY5maUyJhbOwIk9_ ua-cam.com/video/wsJPuhuHaKg/v-deo.htmlsi=d4gkghqFwYpDNNKP
Great video Steve, I'm curious on your thoughts on air vapour control barriers and pitched roofs. Are they required pitched roofs, and if they are, where should it go? I've been watching other videos such as this one, which whilst a top quality build, doesn't focus on vapour barriers beyond the skin of the PIR: ua-cam.com/video/iXKiskcuAFY/v-deo.html Be great to know your thoughts.
All warm roofs depend on robust construction, and from what I can see, that appears to be the approach being taken here. However, all indications suggest that an air and vapour control layer (AVCL) should be installed on the warm side of any insulation. In this case, due to the method of installing insulation between the joists, positioning the AVCL on the warm side would be extremely difficult. As a result, the alternative is to place the AVCL closer to the outside. It is widely reconised that to prevent interstitial condensation, at least two-thirds of the insulation should be above the AVCL. From the video, it appears that no AVCL has been installed. While this does not necessarily indicate failure, particularly given the high standard of workmanship, it does diverge from established detailing requirements from Building Control, NHBC, and British Standards. That said, the foil facing on the insulation, if properly overlapped as shown, may help mitigate potential issues.
In my cold roof it was told 175mm insulation. No insulation is that thick so went for 2 x 90mm. Double the pain fitting each piece in. Fight fight fight it was. Had to be mm perfect too small and it falls out and too big cannot hammer it in. BTW make a 2x3 with a big lump of timber on top, my joists were 225 so used a bit of that. You can hammer it in with that. Warning though hammering it in makes all the dust fall in your eyes 😮 I may make a jig saw attachment to mimic the ££££ expensive festool cutter if there is enough interest. Has to be dirt cheap though.
I cut some of the insulation to make this video literally two minutes cutting it and the dust was terrible. I should've put a mask on but you know I was only making two meter cuts. It's horrible stuff to work with.
The reason for thicker insulation in a cold roof is to compensate for the lack of insulation where the roof joists are. A warm roof has many many advantages over the obvious including consistency of insulation across the whole of the roof without cold bridging by joists, and far less cutting required.
Thanks Steve that is really interesting and helps me understand what I need to be asking when I have my flat roof redone next year on the utility room at the side of the house (I brought the house 1 1/2 years ago) and the flat roof is a kind of cold roof (someone has put a lot of OSB in most of it but it was designed as a cold roof and the vents look blocked) it also has a small leak. I am also going to be building a 7x4m workshop in the garden (no one is going to be living in there) and I was just wondering what your thoughts are on a hybrid roof? here is a link to Liam Griffin of Oakwood garden rooms explaining them, he has a lot of videos explaining them. ua-cam.com/video/EZFcHcxbFbE/v-deo.html&ab_channel=TheGardenRoomGuru . Regards Dylan
I only try to give information that is robust and within robust construction methods when your building outside of thease peramiters you can do what you want it works or it it dose not. have a look at using super foil a very good product
Steve I have watched all the wah through and thoroughly enjoyed! You have answered just about every question I had and a lot of them were around the vapour / moisture, I recently watched this video ua-cam.com/video/xWRLCWmqT50/v-deo.htmlsi=TBUVW0E4Hfpr9gYU By build better things and it has me worrying my plans to put ply in the roof were misguided, but I think you have settled my mind and I believe it is fine, cheers.
I put a flat roof on my extention 20 years ago, followed your instructions to the letter , a fantastic system, the only thing different that I did was to put gutter seal on top of the kerb before putting the osb on to give an extra seal at the joint between the kerb and the osb just incase there was an air gap between the two .
No leaks to date and looks as good as the day it was done , I used torch down felt ,
. Thanks Steve for all of your advise 👍
Steve is literally ahead of the times 😂
Thanks
I never get tired of hearing this stuff, and I've only ever done one roof in my life. I made a complete arse of it.
It's all about learning how to learn this is what they don't teach you at school personally I never went to school but I didn't realise I was always trying to learn and I'm still trying to do that now.
@@SteveRoofer
Learning how to learn is a problem I had all my life. I am 62 and was in my 50s before I realised this was my main problem. It could have saved me so much time if someone had recognised this instead of just telling me I lacked confidence. I’m not stupid, I have a Mensa test result of 133 IQ. Well, better finding out now instead of never knowing. 😂
I always enjoy sitting down and watching a Steve nerd waffle in a subject I really enjoy myself, I run my own company flat roofing operation designs in basically the same way
Thanks for the nice comments. Realistically, I actually enjoyed doing this video. Just took my time waffled on. Wish your opinion though wood on the top is one question I sort of asked and the other one is it's not so much the air vapour control layer but the way it's fitted.
I have vexed over this for weeks and had a consultation with Steve last year. The very important point Steve makes is that the most vapour controlled layer is closest to the inside of the building. If this is done then vapour within the roof construction will find its way to the outside. One way to show this is to download the Wufi programme from Fraunhofer which does a proper condensation analysis (free verison will not give you a UK weather map - I used Brussels as it is not too different). This will allow you to prove that condensation will move out of the roof construction and that no mould or condenstate will accumulate within the building or within the roof construction.
Hi Steve, I love your videos! I have installed many domestic and commercial warm roofs. I always completely agree with what you say! For me, alutrix 600 is the only VCL product to use, and using contact adesive on the wall upstands sticks like 💩 when done properly. Also, I always take the VCL up the timber kerb and finish off on the outside edge to create a better seal. I was always told that you are creating a sandwich, which I hear you say. Thanks for brillant videos, Steve.
This is an episode of Tomorrow's world - revisited ...
I have always enjoyed all your videos and education
I can't believe that I did this 12 years ago thanks for your comment.
Thanks for the video I like seeing how other countries build stuff.
Built my first house over 30 years ago and now on my fifth. Steve putting me on to Alutrix has been one of my biggest "finds" ever. Even more so when you're working slowly on your own. Once you know, you know and it's also a huge big up for the power of youtube for educating and informing.
Thanks Steve. I used the information in your previous warm roof videos to design the roof of my daughter's 'tiny' house. As this didn't need to comply with building regulations, we used 100mm EPS for the insulation. We used Alutrix 600 (with FG35 primer on the vertical upstand around the roof), plywood on the top and bottom of the insulation, and EPDM as the weather-proof layer. The EPS is vapour permeable (about the same as OSB). We took the Alutrix 600 over the sides and slightly down the outside face of the upstand - when primed with FG35, the Alutrix sticks incredibly well to wood.
Glad to hear that the video helped get back to me in about 20 years time telling me that everything was fine and I'll buy you a pint
Why didn't your daughters tiny house need Building Regulations? Any exemptions for buildings that are under 15m2 or 30m2 floor area all state the the building must not include sleeping accommodation. Even if you didn't need to comply with building regulations why would you choose to use such an inferior material as EPS? 100mm of PIR would likely have halved the energy loss through the roof (though still not enough to comply with Building Regs). The tiny additional cost would have paid for itself in no time.
@@mikebarry229 The tiny house was in the rural part of a foreign country where different exemptions applied, and small quantities of high-performance insulation were impossible to obtain. The EPS was a graphite-enhanced version with a thermal conductivity of 0.030 W/mK, so it was about 2/3rd as good as the best insulation. We were restricted on the height of the building as my daughter wanted to keep it transportable on the road network. The U value of the roof is a bit better than the walls and floor.
@tlangdon12 makes sense, I was assuming England or Wales.
Outstanding work.. The best and logical information on warm roof construction out there. Happy New Year to you!
Happy new year!
We do warm roofs. We use low perm barrier on walls and roof to make a shell. Then install staggered mineral wool batts and boards. To minimize thermal bridging. Osb usually has clips between it here on a roof. We use tongue and groove white cedar with our open trusses. In cold, frigid regions (climate zones 6, 7, and 8), dramatic temperature differences between the warm inside of homes and the colder outside creates an intense vapor drive from the inside to the outside. Applying a permeable air barrier on the outer side of the exterior insulation enables the vapor from the inside of the building to diffuse out. The lower the climate zone the colder it is here. Actually in zone 5-4. We do external vapor barriers. Were as Canada and some states do interior vapor barrier. We would have to vent that roof at the wall if heated. To release the warm moist air. Of course its colder here and I am also in maritime climate too. We don't do flat roofs because of snow loads. Nothing less than 4/12 pitch. And are at a 70 pounds per square foot snow load.
I'm not a roofer, just always interested. I've heard both arguments OSB/ply over the top of foil insulation or the tissue faced insulation with no topping and I believe both are credible if done correctly but I'd tend to favour the OSB/ply top in case of future walking on, etc.
Thanks for sharing Steve, I hope you had a great Christmas.
Thanks for the comment
I really appreciate this video Steve, super informing. Would you mind doing a video some time about how to AVCL, insulate, and EDPM detail a skylight/flat roof light? Thank you
send me an email and I will send you a private vide that i have on that
i’ve been doing sandwich system with torch-on for 30years ,had no problems,always picture
frame it ,because you can fix the fascia boards to it 👍
Excellent as always. I need to redo a garage & utility roof that is felted and thinking of changing to a warm roof with epdm
Go for it!
Look forward to getting notifications on your videos. I've just spent the last two days putting on the Alutrix 600 VB on my extension's flat roof, with the FG35 primer (nothing coming apart when using the primer!). I'm going to use tissue faced insulation, with a solvent-based adhesive for an EPDM final layer, I don't like the thought of timber being right below the cold side of the warm roof...
It’s the best, in Ireland the best epdm we use is Resitrix full bond
As I say, the main thing is the vape barrier so good luck send some photographs
Come the warmer months I will send you the video after I've built my garden office - it's being used as a test bed for the main house with what I learnt while working as a sparks in Texas and Cali. They're leagues ahead over there in terms in warm building/ perfect wall construction. Possibly it will be helpful to you and also good for guidance as the 2 climates I've specked it from are a lot dryer than the UK.
Brilliant information as always, thank you Steve. Had no idea foil faced celotex had poor vapour impermeability, I presume that includes the foil tape at joints?
Glad to help
Thanks Steve, very educational 🙏
Very welcome
Fantastic and very informative videos. I've discovered this channel as I want to get a garden room built. From what I can tell every company will build a cold roof and cut holes in the insulation for lighting.
I assume the extra cost in materials, the extra height a warm roof adds, more time and even the ability of correctly sealing it all up is why most builders go for a cold roof instead?
I can't understand why people do these garden rooms the way they do it's a complete no-brainer to clad the outside of the building with super quilt around the walls and over the roof no-brainer think of it like this in the winter what do you do? Do you put your jumper on i.e. pull your arms through it so everything is inside and nice and warm or do you eat your jumper and put the insulation in the inside insulation on the inside? Wrap the outside of the building in insulation?
By way, by the way about the jumper of words from a very wise man and not my words
The disadvantages of a warm roof are listed in your second paragraph and they are all disadvantages for the contractor. The disadvantages of a cold roof are in your first paragraph and they are all disadvantages for you. A cold roof done the way you describe without effective vapour barriers and pockets cut for lighting will cost you dearly in extra wasted energy and premature roof replacement. Stick to your guns and find a contractor that puts your needs ahead of theirs.
As regs march on. More emphasis is being put on testing like BRoof T4. As non combustibles become the desired route.
There has been huge changes to what’s being supplied on major projects. Due to this “grenfell” effect. And it is now being frowned apon to include timber within a flat roof system.
I work for a major flat roof manufacturer (well the uks largest) and inspect said projects. A quality AVCL membrane is a must. And it amazes me through my inspections how many “roofers” do not apply this important layer correctly. And how many “smaller” outfits will omit it altogether.
I am applying your advices in Siberia. In extreme winter temperatures. But we can't have a flat roof here. Too much snow and so the beams are too expensive. But we can do the same with a regular roof. Just by using a standing seal metal roof over the osb.
Terrific & shows there are expert installers out there. Sadly councils like Westminster never use quality smaller suppliers, instead relying on having a small number of big contracts with Moron Swindle, who then push any specialist work including roofs to tiny hopeless subcontractors One of these tried to cut through the ring main foundation in our listed building when replacing a waterline (they claimed they didn't and then said "what's a ring main foundation") then cut through an 8' solid slab for access into a flat & filled it in with bagged rapid set cement with no reinforcing/rebar (obviously no supervisory oversight or sign off).
As a Building Surveyor and Engineer I have to confess that I have never heard of a "ring main foundation" either. If I were to guess I would assume you mean a piled foundation, as that typically includes a ring beam linking the pile caps together, or possibly a raft foundation which typically includes a toe beam around the perimeter.
Yes, he's probably talking about a ring beam of some sort but yeah, there are a lot of people who don't know what they're doing out there
yes they certainly are a lot of people out there that don't know what they're doing
Really useful. Thank you.
Glad it was helpful!
Tiled roof to warm roof video would be handy.
Yeah, that's what I'll be doing quite soon
@@SteveRooferGreat! I’ve loved these two videos, and learned a lot (especially about available materials). But would really appreciate something similar on really upgrading attic insulation. I’m thinking that I can apply the principles, but worry about what happens at the eaves of a stone built slate roofed cottage. Where the eaves are virtually impossible to access internally? And I want to retain some storage space for suitcases and, of course, Christmas decorations! etc.
Also something that never seems to get addressed is making that space rodent proof or at least resistant. (Field mice want to move in annually around Oct/Nov)
Steve, what's your thoughts on glueing the t@g osb like you would with floor sheets? Great videos btw
no need to if you've put it down screwed it down properly it's not moving anywhere, anyhow
@SteveRoofer What about annular treated ring nails?
@@ruddy6367
No nails, there are specifically designed fixings for this
No nails that correct
Hi Steve, I do not see the link for your video about Sarkin felts. You mentioned you would add it? Any ideas? tks Paul
Nice update Steve - we’ve got a utility room with a concrete flat roof that condensates badly inside - we want to put a warm roof on it but can we use the epdm that’s on there now as a vapour barrier under the new insulation as it’s in great condition still or would it be best to remove it & start again from scratch - thanks lee .
Very timely, I'm building a pitch warm roof for my extension, I have bought marine plywood for the lower deck,the 600 VCL product, tissue faced insulation, and dpm above it. I don't need an upper deck I reckon, can you confirm this point? Also, what brands of thermo broken fixings do you recommend for the counter batten/batten installation over the DPM? Thanks so much, your videos are super educational, I picked up in this one the need for a coating for the walls. Btw, a friend recommended a heat recovery extractor for the kitchen which makes lots of sense after all these efforts going into sealing the building envelope..
okay reading your details above so you're gonna use some kind of marine plywood for the lower deck that's great 600 VCL product tissue faced insulation that's good and a DPM above it? Why would you do that purpose? Do you think that is going to serve you don't need a DPM above it. Okay I get my firmly broken fixings from a company called fix fast.com. If you can't find them just give me a email and I will send you a link to them. Good luck. Speak soon send me photographs of it being constructed even you never know, I might be able to use them. Speak soon.
@@SteveRoofer I meant a breather membrane, not dpm. Thx for the fixfast tip. So in that configuration of a low pitch roof, would you keep an upper deck or just do away with it? I will send you pictures, I've got a good carpenter and a good detail in mind for fixing the counter batten to the end of the rafters. I'm just a bit uncomfortable with these fixings throughout the bm/insulation/vcl to hit the lower deck. I take it you have to have all the fixings hit the rafters underneath to minimize chances of any bridging?
@@michelleconte8428what roof covering are you having on your battens and counter battens? This is all important info. Your fixings need to go into the rafters for strength and nothing to do with thermal bridging, though it will reduce that aspect too. What purpose would a timber deck over the insulation serve? It would only increase the vapour resistance of the roof construction at a point where you want it to be breathable.
@@mikebarry229 I have low pitch interlocking clay tiles. Ok, so it sounds like we're in agreement, the upper deck is not serving any useful purpose. I thought it might from a structural standpoint, but given that no-one will walk on that roof...
@@michelleconte8428 so long as your tiles are OK for the shallow pitch you should be fine. The ply under the insulation and directly connected to the rafters should give you all the bracing and structural integrity you need, at least for the rafters. If you are using roof trusses they may need additional bracing to internal compression members.
All depends on on the roofing system you are doing. I mainly use single ply pvc. Which does not need ply board on top of the insulation. Also some single ply manufacturers don’t like you using OSB as the deck as it does not hold a screw as good as ply for screwing the membrane down.
totally agree with you and PVC is one of the better membranes out there. I always put it just a little bit above EPDM however it does come with the cost and as I'm primarily in the domestic world not everybody wants to use it and I also agree and I hope that this came over in the video that in the perfect world timber would not be used in the construction above the air vapour control layer.
@ your videos are brilliant done. I always tell my customers to watch your vids so they can understand a warm roof and cold roof, to better understand them.
Great video, and your advice is invaluable. Having the opinion of someone who has seen where things go wrong is the best guide . I am about to install my own warm roof this spring and ive watched all you videos. Its a medium sized roof, not complicated, one roofligh backing onto a new extension. Ive done a few grp roofs on the past and plenty of pitched roofs. For a competent person but not a professional flat roofer any advice on what to go for on my own home? Liquid rubber, epdm, flexible grp?
Flexible GRP is a bit of a contradiction. There's no such thing, but it's a good marketing ploy. Personally, EPDM or felt make sure that you have good falls on the roof that is the key good drainage no standing water I cannot understand people who put a minimal fall on the roof basically 25 mm in every 1000 is what is required but what the hell? Why not? Double that or quadruple? I always do if possible.
Brilliant and much appreciated. I made sure I had pleanty of room to the cavity tray on the new extension so I will build the fall in.
At last, it now makes sense. Just to clarify in this warm roof construction , there is no ventilation required at all ?
No where would you put it? But I'm really tired that you're actually getting there. Believe it or not there many many people don't understand this like I say on the video under the air control layer is internal so there's no where where to vent
No air movement at all in a warm roof...not even an ant's fart!! 😂😉
Great informative video, time flew by watching it, looking forward to the ridge videos, as have that as a job on my house in the near future. P.S. the promised links aren't in the description.
I've been adding them as I go on but the one link that there take you to the information on the AVCL and so on
This is a link to the new supplier of AVCL,s
steve@stratawaterproofing.com
www.stratawaterproofing.com
Get back to me if you use them and tell me how you get on
@@SteveRooferI purchase classic bond epdm from this company as there based here in N Ireland aswell as there sticky back VCL I've had no problems with them apart from price. Cheaper to buy from England but then delivery cost can be expensive. They sell many different flat roof products but I've been asking for a long time to get trained on the pvc system (the name of product escapes me right now) but still waiting about 3 years now
Hi Steve great level of detail shared. Thanks.. just a question regarding using 18mm osb on top . If hitting dew point on the underside of the OSB will it not eventually cause the OSB to rot? I know you say Moisture evaporates out eventually .. I have head knauf do cement boards for warm roofs. Any views on using them instead of OSB?
Personally, I think everybody is overthinking this. All you need to do is get the air vapour control layer perfect like my example wrap it everywhere and put a top on it. It's a sealed unit with only the moisture in it locked in. It's a sealed unit. nothing can go wrong.
As a architect, I would always recommend tissue faced and no ply or osb on top. It’s better to bond the rubber to insulation with contact adhesive.
what if you read between the lines that exactly what I'm saying? However in a real world you can't always do that.
I thought I already answered this but if you read between the lines, I agree with you but people want to walk on the roof and they do not like it soft
@@SteveRooferreal world is important here, flat roofs have been around for more than 100 years and the vast majority have been constructed as cold roofs with a timber deck. Consequently home owners and trades people generally have an expectation that they will be able to access a flat roof for maintenance purposes. At a domestic level at least I feel the risks of installing a timber deck between the roof membrane and the top of the warm roof insulation are insignificant compared to the risks of not doing s. For commercial buildings maybe less so. For the reasons you explain if a timber deck does deteriorate in this location then you have serious problems with the roof that need to be addressed regardless of whether you have a timber deck or not.
Why don’t you like glass fibre on tongue and groove osb? Movement? Cracking? I just got a job done with this spec, looks solid to me but I’m not that clued up on fibreglass.
Thanks Steve. Very informative. Your point about the ply at the end.. does this hold true on cold roofs? Can the deck go onto the joists and full fill insulation between, assuming there is a very high performing VCL? I’ve drawn this up and have firrings above the structural deck and another layer of ply with steel roof finish. There is 50mm minimum ventilated space. The structural deck is required by the engineer. I’d like to avoid ventilating between the firrings and also a 50 mm cavity under the structural deck so full fill insulation would be better.. what do you think? hope this makes senses. Thanks
The short answer is no - don’t build a cold roof. They no longer work effectively.
The issue lies in the insulation placed underneath. While insulation used to allow some heat loss, which kept the cavity warmer and allowed for drying potential, today’s thicker insulation changes the thermodynamics. Without that drying potential, cold roofs stay damp for longer, increasing the risk of problems.
In my opinion, cold roofs are no longer a robust construction method. If you reduce the insulation, they may function, but at the cost of significant heat loss - you can't have both
The short answer is no - don’t build a cold roof. They no longer work effectively.
The issue lies in the insulation placed underneath. While insulation used to allow some heat loss, which kept the cavity warmer and allowed for drying potential, today’s thicker insulation changes the thermodynamics. Without that drying potential, cold roofs stay damp for longer, increasing the risk of problems.
In my opinion, cold roofs are no longer a robust construction method. If you reduce the insulation, they may function, but at the cost of significant heat loss - you can't have both but I have some tricks up my sleeve that will be coming out very soon. I have two new ways of doing warm roofs that don't need ventilation. One of them is extremely interesting and there is a lot of data saying that this works if you give me a contact by email or you wanna phone me at sometime I'll talk to you through it but I haven't got enough information to put the video out yet so I'm keeping it up my sleeve at the moment
@@SteveRooferThanks for your reply Steve. Sounds really interesting, I’ve sent you an email on your info@londonflatroofing
I have just done a flat roof with 150, is it worth while doing something below as well insulation wise or is 150 sufficient.
Hi Steve, how are you fixing down the insulation and the top layer of osb or ply ?
I see allot of people winding screws through the hole build up and into the joist but I can’t see that being any good for the roof!
Could you explain whether using this VCL is fine for liquid rubber roofs? and if you can recommend a liquid rubber system
Hi Steve. What would you recommend for a VCL for a cold flat roof? Any recommendations for tape? Do you go bitumen tape? If you’ve already done a video like this one but for cold roofs then a link would be great.
the green one that I show on the video which I can't remember the name of is the one that you should be using, but you know it's really expensive but it's time you buy all the tapes and everything. It's a real mission. I did a example a few videos back I can't go back and look takes too much time, but it's out there and it does show the different materials. Just look up wa, sorry cold roof barriers something like that and I named them all there and I also share how to do it on a test test week that I had good luck. Send me photos and videos as and when you get them speak soon.
Hi Steve,
Thanks for all the informative videos!
I'm doing a lot of research since I’m planning to build my own warm roof. The plan is to mechanically fix the PIR insulation using thermally broken fixings (plastic + screw). In doing so, I’ll be screwing through the air vapour control layer.
Unlike in your videos and advice, I won’t be using an Air Vapour Control Layer with a sticky back (e.g., Alutrix 600). In the Netherlands, the price of AVCLs with a sticky back is enormous.
What would you suggest to keep the AVCL airtight? Should I dip the tip of the screws in glue or silicone sealant to seal the holes they make in the AVCL?
The roof buildup be: 18mm Underlayment - Miofol 125AV (AVCL sd=1500) - 100mm pir isolation 2x aluminium foil facing - 20mm pir Isolation with tissue facing - EPDM.
Thanks!
Good plan with the warm roof! I totally get the cost issue with Alutrix. You might want to check out SIGA Majrex® - it’s a vapour control layer that works like cactus skin to keep moisture out. Look up “compact roof” on their site and check their blog. I’ve done a couple of these and I’m gathering data for a video soon.
Let me know how it goes!
17:58 where do you put fixing on a roof of say 6m/6m? Nothing through the insulation, glued in the middle to keep it down?
you always put more around the outside edge and then, as appropriate, realistically on the inside does depend on whether you're using T+G ply or not but obviously you need to put down enough and that becomes obvious when you're doing it because it becomes really robust under foot
Would you consider hemp insulation batts?
If you are doing a vapour open system, that's not a problem, but it has to be designed correctly
So you glue the insulation on the air vapour barrier? No screws anymore? In the past you had roofs failing because of moisture in the insulation ,if I am correct to remember. Thanks, Dennis
you remember correctly? I like to always use mechanically fixings however more and more now people are gluing insulation down. It's a choice scenario personally I do a bit of both these days.
Hi Steve
Do you need to insulate internally as well? Between the joist like normal?
No, not at all. If you get the insulation outside done correctly you don't have to put some inside. There's an interesting theory here in the winter. We always put our sweaters on. We never eat them if you eat them you're gonna get cold on the outside! Hence why always put you insulation around the outside.
@ makes sense mate.
With that theory, you wouldn’t do a cold roof at all?
Are you talking converting from cold to warm?
@ no mate
New build or extensions?
Sorry but there is something I quite don't get : you advert for a 130 green vapor barrier (VB) on top of the 13mm plaster board, then a vent space, then a 18mm OSB, then a +/- 1300 VB, 150mm insulation, Plywood, then a +/- 200 VB on the very top.
You argue that the top layer must have a lower SD value than the interior VB so to a oid condensation. But what about the internal green VB with a 1000+ SD VB on top of it? Acording to your logics we may get condensation at this place....
Could you please elaborate?
interesting just wondering if using T&G osb what about expansion gaps you are meant to leave between sheets?
Don’t need expansion gap between sheets. You have to leave 25mm at the abutments only. And if you do use fibreglass lay your osb up side done so the resin flows into the gap and you will have a stronger joint
@Gyulaffy has answered this very well you don't need these expansion joints in the system but you do around the outside
Another great video as always Steve.
What was the name of that paint on adhesive to stick the barrier to the walls?
I sent you an email today in regards to using battons on a cold roof example
anything that makes the wall not dusty but we use spray adhesive, which is a contact adhesive but anything like that will do as this stuff really sticks to anything.
This system seems great but if you make a swimming pool how would they defect a roof leak in the future?
These videos have just convinced me not to get a flat roof on my extension. Thanks
Thanks for the informative video.
I am in the process of starting an extension and would like some guidance/advice.
Please let me know a suitable time to contact you.
Thanks
Rizwan
Why isn't there a ratio of 5 between SD value and the MNs/g for all the materials in the table? I assume just a mistake somewhere?
I thought there was that what I've based it on
Ah yes in the video it's correct but there's a spurious reading for Alutrix in the table in the linked guide
OK Will go and have a look
Keep adding to insulation thickness and it's becoming, or already is diminishing returns. Who is ever going to notice the difference between 120 and 150mm of insulation, when the room below, itself needs ventilation to be healthy. Plus people are knocking out entire lower elevations to be replaced with huge bifold doors, the wall insulation going in the skip!
Yep, I think you're absolutely right. Well said.
Putting any thing wood based on top of the insulation is insane.
How would you make a warm roof suitable that you can place decking over the top without it sinking into the soft insulation or if you want to put solar panels over the top waited down? How would you transfer that weight?
Not quite there yet mate 😂
What do you need? Help with? Send me an email or just do it here
In short, just use pitched roof. Flat roofs are just maintenance nightmare.
They're using glass faced gypsum as a coverboard in the US. No organic material, no mold. With smart membranes you can use mineral wool to avoid using petrochemicals, which will be popular for some clients, and it allows for any moisture on the membrane to dry inwards on warmer days.
Asiri Designs does an excellent series on the building physics:
ua-cam.com/video/-6y2ooXxqfU/v-deo.htmlsi=ZY5maUyJhbOwIk9_
ua-cam.com/video/wsJPuhuHaKg/v-deo.htmlsi=d4gkghqFwYpDNNKP
Great video Steve, I'm curious on your thoughts on air vapour control barriers and pitched roofs. Are they required pitched roofs, and if they are, where should it go? I've been watching other videos such as this one, which whilst a top quality build, doesn't focus on vapour barriers beyond the skin of the PIR: ua-cam.com/video/iXKiskcuAFY/v-deo.html
Be great to know your thoughts.
All warm roofs depend on robust construction, and from what I can see, that appears to be the approach being taken here. However, all indications suggest that an air and vapour control layer (AVCL) should be installed on the warm side of any insulation.
In this case, due to the method of installing insulation between the joists, positioning the AVCL on the warm side would be extremely difficult. As a result, the alternative is to place the AVCL closer to the outside.
It is widely reconised that to prevent interstitial condensation, at least two-thirds of the insulation should be above the AVCL. From the video, it appears that no AVCL has been installed.
While this does not necessarily indicate failure, particularly given the high standard of workmanship, it does diverge from established detailing requirements from Building Control, NHBC, and British Standards.
That said, the foil facing on the insulation, if properly overlapped as shown, may help mitigate potential issues.
In my cold roof it was told 175mm insulation. No insulation is that thick so went for 2 x 90mm. Double the pain fitting each piece in. Fight fight fight it was. Had to be mm perfect too small and it falls out and too big cannot hammer it in. BTW make a 2x3 with a big lump of timber on top, my joists were 225 so used a bit of that. You can hammer it in with that. Warning though hammering it in makes all the dust fall in your eyes 😮
I may make a jig saw attachment to mimic the ££££ expensive festool cutter if there is enough interest. Has to be dirt cheap though.
I cut some of the insulation to make this video literally two minutes cutting it and the dust was terrible. I should've put a mask on but you know I was only making two meter cuts. It's horrible stuff to work with.
The reason for thicker insulation in a cold roof is to compensate for the lack of insulation where the roof joists are. A warm roof has many many advantages over the obvious including consistency of insulation across the whole of the roof without cold bridging by joists, and far less cutting required.
Thanks Steve that is really interesting and helps me understand what I need to be asking when I have my flat roof redone next year on the utility room at the side of the house (I brought the house 1 1/2 years ago) and the flat roof is a kind of cold roof (someone has put a lot of OSB in most of it but it was designed as a cold roof and the vents look blocked) it also has a small leak.
I am also going to be building a 7x4m workshop in the garden (no one is going to be living in there) and I was just wondering what your thoughts are on a hybrid roof? here is a link to Liam Griffin of Oakwood garden rooms explaining them, he has a lot of videos explaining them. ua-cam.com/video/EZFcHcxbFbE/v-deo.html&ab_channel=TheGardenRoomGuru . Regards Dylan
I only try to give information that is robust and within robust construction methods when your building outside of thease peramiters you can do what you want it works or it it dose not. have a look at using super foil a very good product
@@SteveRoofer Thank you for the advice about super foil I will have a look into it.
First 😁
You have to watch it all the way through, though it's half an hour long and I only posted 20 minutes ago?
@@SteveRoofer I'm half way through at the moment 🤣
ok tell me what you think when you get there
Steve I have watched all the wah through and thoroughly enjoyed!
You have answered just about every question I had and a lot of them were around the vapour / moisture, I recently watched this video ua-cam.com/video/xWRLCWmqT50/v-deo.htmlsi=TBUVW0E4Hfpr9gYU
By build better things and it has me worrying my plans to put ply in the roof were misguided, but I think you have settled my mind and I believe it is fine, cheers.
Thanks