It's time to thank you. I've used your videos to build 2 walls, insulate my garage and tank a wet room. You explain things so well that I understand and can question things in my head. Insulated summer house / office is next which I'm hopping to start in the next month or two. I still bring in the pro's where needed, but understanding what is going on really helps and I think just raises the standards as a whole. Thank you!
Hi lads, You know what, I am level 6 NVQ (not very qualified) site manager, level 3 carpenter and joiner, and intermediate qualifications in Brick laying, plumbing and plastering, (also a fully qualified Locksmith), with 33 years of mud on boots experience, I've forgotten more than most people actually know, but...... I literally LOVE your videos and pod casts, (only found you the other day, so alot of catching up to do),very informative entertaining AND engaging, even if you are shandy drinking Southerners. Keep up the awesome work 👌
Nige Never touch shandy or larger. Give me a pint of best bitter any day. Unfortunately the number of pubs now serving ale are fewer than they used to be.
crazy how the neighbours would be annoyed if the roof was 120mm higher... I would NEVER EVER EVER be that kind of neighbour. Why would they object to 120mm? What difference will 120mm make to them? Crazy! Anyway, thanks for the video! Very helpful
Very clear and helpful, nice video Rodger! We're always doing these sort of extensions and when the joiner talks to me about hot and cold roofs I'm always bamboozled 😂😂 look forward to see the next video on this project bud!🍻👍
Never really thought about the subject before Roger but in many big old houses they had cellar and attic spaces with air grills below the floor space for the air to circulate. I was lucky when we bought our 300 year old 3 bedroom cob cottage with a thatched roof (cold roof). The 3 foot thick cob walls are build off a rubblestone plinth with no foundations or guttering, the ground is hard clay and stone. There was bad damp when I moved in because the walls were cement rendered and it had been a holiday home for about 15 years which had caused all the damp issues and rotted the timbers on the damp side of the house because I have a hill behind the house whose gable end faces into the hill and in front of that there is a 25 foot deep stone lined well, the water line is about 4 feet below ground, never higher and is only low during summer. Since I put in a French drain along the back side of the house and lime rendered the place we've have no more damp issues. The first floor ceiling is wooden lath & plaster (the walls are reed and plaster), a thick layer of haired course lime mortar and a single layer of thick top coat white lime skim 5 to 6ml thick. Another property of lime walls is they absorb moisture and CO2 and give you better acoustics than cement or gypsum, a friend in nearby Stogursey has plastered his internal walls with clay which has even more amazing qualities. It can be expensive to do but, done well it should last a life time whereas modern builds are designed for about a 40 year life, even a strawbale, single floor structure would last a 100 years. Above this ceiling line is the triangular shaped attic where, between the joists you can see the back of the ceiling and the folded nibs of that 200 year old, haired lime putty mortar and on top of that, between the joists are a few rolls of Rockwool insulation with a 5 foot air space before you see the underside of the straw roof. It's relatively dry. In some of the bigger houses they'd put a thick layer of tamped soil and sand which would be good for the sound proofing and insulation properties. During the night, summer and winter, we sleep with our bedroom window open and during the day, unless somebody is home, everything is shut up. Up the road is an equally old property which has a double-Roman, clay tiled roof, when I climbed up to look there was no roofing felt and it too was dry. As you said on one of your rants, there's no point having an air-sourced heat pump, if the home isn't well insulated inside. I'm house rich and cash poor and can't afford one but I would like a ground-sourced heat pipe, they do work, I would also like some solar panels please. It would help the planet if we all had solar, wind and thermal generating capabilities with storage capacity for any excess power with every home as standard and, if you have a small garden, a compost heap is great for all your organic waste. Ours is barely large enough for the herring bone pipe to the septic tank which is emptied every year (£250) and is cheaper than the mains sewage bill I'm told. We've go no government grants, none available, or help with lower VAT for sustainable buildings, and it was bought to be our family home and so long as it continues to be repaired with like for like materials it should last another 300 years. keep up your interesting topic please, it's healthy when we can all rant.
Thanks so much, just about to build a warm roof for my conservatory. Amazing to see how literally none of these "kits" do not include the ventilation for the cold roof.
Built an extension on my house under the new cold roof insulation regulations, resulting in a permanently cold room, took the roof off 18 months later and made it a warm roof, now have a lovely warm room.
Good explanation for people that don't understand the difference. 1 thing that would be better for ventilating the dead spots created by the lantern would be to counter batten the roof the opposite direction of the joist to create a cross flow ventilation throughout the whole roof. Although you increase the deck height by 25mm you get rid of the need for unsightly mushroom vents everywhere 👍
I did wonder when mushrooms kept being mentioned how the neighbours concerned about the height of the roof would like the mass of mushrooms there'll be instead.
We know that channel well and he is great. We have used that ventilation detail in the past but, as you may see it would have come up above the parapet wall and upset the neighbour
@@georgeturner6648 Orangery are permitted developments, within certain parameters. Then it's permission from the neighbors. They may of had permission, but then the neighbors changed their mind, and to stop the ball ache of courts and council. Which you may or may not win. Especially if you lose you have to pull it down. Sometimes it's easier in the long run to just go to what's permitted without neighbors consent.
Nicely done, I did a little office using warm deck. I stopped the joists at the wall plate, but extended the OSB and 4 inch insulation beyond to create a 200mm overhang. Then sandwiched the edge with 2x4 so I could hold it all together. I only did this to avoid creating an ugly thick fascia that was 300+ tall, instead there's a neat 150mm fascia with the gut attached.
Great video Roger explaining the key differences between a warm and cold deck for a flat roof. My comment is on a warm deck. Like a lot of information out there the principle is illustrated by a cross section and details of the layered structure above the joists. For the void between the joists it is always made clear that there must be no insulation between the joists as this will lead to the rising moist air through the ceiling being cooled by the insulation and effectively producing a cold deck but with no ventilation. It would be really good if you could explain the detail to produce the sealing around the perimeter of the void space when an existing old flat roof is being replaced. The joists are above the wall and open to the air when the original fascia is removed. Your video includes at 1:35 'All this area here [between the joists] is warm. It is within the heated area of the house' which is fundamental. I have only found one set of videos by @SteveRoofer describing and illustrating the inclusion of insulation around the perimeter between the existing wall and the underside of the new deck. The principle is clear in CNCD-053. With just a new fascia board and no perimeter insulation the air in the void between the joists will experience some cooling defeating the basic assumption and potentially achieving the worst of all worlds. The wall cavity will be within the void space and this will also add to the cooling effect depending on the quality of the cavity insulation. This is all obvious to me after not much thought but seems to not be fully grasped by the roofing industry when you ask for a quote and for a description of the planned work even by reputable companies.
Thanks, excellent video! Simple answer - badly installed cold roofs are bloody freezing when the builder who owned your house doesn't air seal between the Kingspan slabs and the joists. It's basically external temperature just above the plasterboard.... 🥶 Also just found out he didn't stick a vapour barrier above the plasterboard either. 🤦♂️🤦♀️😤
I did my flat roof on my lounge 15 years ago. Plaster board, fibreglass, OSB and felt. No sweating, no damp, no problems. Still as good as the day I did it. I can't help but think that a lot of this is snake oil and more money for the men in suits. Great explanation Roger, as always.
My friends house lasted four years due to moisture building up in an unventilated roof space. It is happening all over the place and it is largely due to modern building techniques.
Ever thought about fitting cross battens running the opposite way to the joists,this creates a continuous air flow of 20mm. No need for mushroom vent. As long as you have.front and rear air soffit/ facia and abutment vents.
Can also set the circular saw to 20mm and cut a notch out the joists. Obviously it slightly weakens the joists but we usually over engineer flat roofs anyway! Iv done it that way before and was really fast and much better than drilling holes as they get clogged easily
@@chriscoulson7684 You're not a structural engineer are you! Notching out the top or bottom of a joist doesn't 'slightly weaken' it - it is the worst place to cut it. The bottom is in tension and the top is in compression - somewhere in the middle on the neutral axis there is no stress.
Excellent stuff roger, as a building control surveyor the most common mistake is a warm roof with no decking and VCL below. Happens all the time! Every PIR supplier will ask for an 18mm deck with the VCL
Thanks Roger, excellent explanation to a bit of a head scratcher. Am going to replace my old plastic roof on my conservatory and had been trying to weigh up the best way of tackling it but you just explained it in less than 10 minutes!
Thank you for sharing that knowledge. In NZ we build a lean to extension with a mono-pitch roof. Plaster board 200mm joists, vapour barrier then corrugated Iron. The Insulation is Pink Batts skillion roof insulation. The insulation had to be specific due to the insulation loft limitation giving allowance for at least a 20mm gap - I now further appreciate what that gap is for. More so it gets me to thinking about flashings and how well they can release water on the inside without letting water in. Hopefully the building codes we built to are correct.
Come see the uk new builds a meter of installation double glazed windows its like being trapped in a oven. ive not closed mt windows all year ... on the inside 30 mm pipes for the plumbing 15 mins to refill a toilet.. but they are alot cheaper than million dollar nz .
@@JONO3679 Sounds like a pressure issue or restricting washers to the toilet water supply? Many 'eco' toilets these days use too little water which can cause more issues - blockages - than having a decent flush volume.
My thanks to Skill Builder and Roger - now all i need to know about warm and cold flat roofs. Infact my new extension Surrey side of Gatwick a semi-detached and all flats are cold. my new extension will be warm and work to change my current flat roofs to warm but will leave attached neighbours as is. with some magic (in the drawings) for the builder !!
Great as always Rodger. I have a 15-year-old log cabin. It's perfect inside but a bit dated on the outside. I spend around £100 per year maintaining it as well as the cost of heating. I am about to insulate it on the outside all around and have the products but not 100% sure of which way to have the insulation, membrane etc. I don't want to insulate the inside as I like my LOG cabin. I have 60mm Kingspan sheets (got them cheap so can't change) a breathable membrane, PVC cladding for the walls and box profile sheets for the roof. I was intending to stitch the membrane onto the outside walls then Kingspan held with 2"x1" battens and the pvc cladding onto this. There would be the 1" air gap behind the cladding vented at the top and bottom with mesh to stop wasps etc. The roof is 20mm t&g pine and is felted. The felt needs replacing so was intending on removing this stitch the breathable membrane on top, Kingspan, 15mm OSB then the box profile sheets directly on top. Do I need to change the membrane for a vapour barrier? If so where does it go? Do I need an air gap roof or walls? Any advice would be appreciated as I'm getting conflicting messages on other forums, everybody seems to be an expert
Great videos! I've tried reading most comments so apologies if it's been asked before.. I'm currently starting a new build with a pitched roof. Strangely enough when you search for a warm roof, most videos, info etc. are in the context of a flat roof. Not a great deal of warm roof examples of a pitched although I have seen a handful of insulation companies i.e Kingspan, Tyvek with demo videos and illustrations of this exact setup, though they leave a lot to be questioned, they do show this is a practised method. My main concern really is only a problem when you have a pitch and that is the limited shear strength of the very long screws/insulation fixings that have to sandwich the battens to the rafters with this approx. 100mm of soft insulation board in between that provides no stability to these screws. I hope this makes sense, it's a question I haven't quite seen addressed before, thank you for your time!
Hi Michael You are right to say the focus is on flat roofs but a pitched warm roof is fundamentally the same. The best way to approach it is to counterbatten on top of the insulation in line with the rafters. You can buy stainless steel helical fixings. They are twisted so that stops them bending and they won't pull out. thorhelical.com/product/warm-roof-fixings/ Once you have the counter batten fixed you just batten out the roof in the same way you would on a cold roof.
I think i would have gone a cross the 9x2s with tile batten so the whole roof is connected and reduce the number of roof vents. Not only is all them mushroom vents going to cost a lot especially as they have to be built into the roof covering, they will look facking ugly. Good vid Roger 👍
Hi Tony Good idea but we had the deck down and we were going with the warm roof so we didn't want to rip it all up and counter batten. Also the counter batten doesn't give enough cross ventilation on its own. The whole thing is a ball ache and it is all down to a neighbour who said it was O.K and then said it wasn't.
@@SkillBuilder Remember- never ask the question if you don't want the answer. If you have permission for the higher warm roof, go with it, and don't ask the neighbours for their opinion
@@rossbuchanan7632 ...building regs? It sounded to me like there was a veiled mention of the fact that some arch holes can be nay bores. i for one wouldn't like to challenge a regulatíon and have to rip off the roof and then live with the people who opposed me in court. Ridiculous though, that it's a matter of less than a foot.
@@SkillBuilder Had loads of grief with neighbours. Not about height, they just don't like seeing people get on! Can't win, don't even try. Do what's best for you! Just make sure you stay within your rights. They will complain !
I have a large flat roof over a kitchen, 75mm fibreglass between the joist with cross ventilation from soffit into the pitched roof void. Its 45 years old and its fine - the fibreglass gets a bit damp in the winter but it always drys out quickly enough. The original chipboard deck failed after 10 years so I re-boarded it with marine ply and had high performance polyester felt laid on top. 35 years later still no leaks. Sometimes low tech works just fine.
Warm or cold roof, always avoid moist getting in the construction from the warm side of the construction, Make a 100% damp sealing above the plaster board.
I'm surprised the neighbour is even aware of the 'options'. This is what was granted permission, these are the plans and dimensions, and this is what is getting built!
When I put up my extension , It was a cold roof because of the design I wanted. I used foil back pb and foil taped all the underside of the joists to the foilbacked Kingspan so there could be very little chance of any moist air penetrating. Redbrick vents to the front and proprietary vent escape vents to the rear. Hmmmm, forgot about the dead spaces though, gulp ! That said, ten years in and no problems as yet.
The neighbours annoyance at the hight of the orangery should have been noted in the permission stage before the project started. Once permission is granted there's nothing they can do
Is it normal on the roof to fit 18mm plywood then osb on top before the grp . Or is this overkill and trying to rectify a problem with the plywood , thanks
I built a garage extension where I didn’t have the height for a warm roof or the joist depth to achieve the required R-Value with venting, so I used Closed Cell Spray Foam. It is allowable under the Canadian Building Code for use in unvented roofs because it acts as a vapour barrier. Pricey though.
food for thought. i have two flat roof extensions. both had no air space, both rotted. hopefully the roofer done it right this time. i have edpm roof covers on now.
Jeez, that's interesting I did a substantial repair job on my roof myself (Cold roof) I did my research and I knew the principle of the through flow of air and I didn't really do a great deal of work so I assumed the existing structure would work in the way it was designed. I had serious condensation problem. The previous owner - my father in law had put fibre glass in between the joists laying directly on top of the ceiling plaster board. My analysis of the problem was the moisture was getting through the boarding, and then hitting the cold air beneath the tiles the condensation accumulating under the tiles and dripping into the fibre glass and eventually making contact with the plaster board. I felt that the fibreglass that was filling almost all of the cavity and was reducing the air-flow and replaced that with GRP. That then left a good gap for the air flow. Not had any problems since (4-5 years now) so assumed I'd done a decent job. I'm going to check that out when the weathers good. PS it's a very shallow angled roof 25 degrees. Good vid.
Roger for me cold is always the way to go as long as it’s vented properly, around the Sky light/ Lantern you can do a vented upstand where you cut the ply short 25mm and run 50x25 batten vertical and leave the upstand ply 25mm short at the top thus creating enough draw for the air to move, it’s what we always do.
@@denty32 Zero of either. Cold roof needs more work if done correctly and down lights can be a pain. Much easier running out full sheets of materials from above deck. The extra height can look unsightly, that is true. Don't get me wrong, if it works it works.
@@TurinTuramber every flat roof / low pitched roof I get called out to inspect is 99% a warm roof with poorly fitted Vcl. Every one thinks warm roofs are easy to install until it goes wrong. It’s normally a SVP or flue that didn’t get fitted at the time of installation.
@@denty32 On a clear roof like an outbuilding there aren't really any interruptions so goes down super easy. Some roofs are busier than others. Also cold roofs thermal bridge like mad, Roger didn't mention that I think.
I built a flat roof with cross battens. It was a continuous problem with the boards moving about and cracking the waterproof layers. A butyl membrane would have been ok but the felt I used was a nightmare I seriously regretted not nailing the boards solid and using mushroom vents.
Roger, firstly great explanation. Can you place a link to the grp mushrooms that you would recommend between the joists, and also the upstand ventilation product you also mentioned please.
You talk about the warm side sand cold side of the insulation. Where are you located? What if we live somewhere that uses heat half the year and air conditioning half the year? What's the cold side?
Great video Roger. I wonder why you didn’t opt for counter batten over the top to negate the need for the GRP mushroom vents? Just pitched a lean to roof and I’ve counter battened and put vented soffit on all three sides.
Just seen this after commenting myself about cross flow ventilation. Would of been a much better way but rach to there own and we all are still learning
I used the 25mm multilayer foil insulation for a warm roof, supposedly equivalent to 225mm of fibre insulation, but adds no more than 40mm with the counter battens. It all seemed to work well. I'm planning an orangery type extension on the house I'm buying.
Where do you put the electrics/extractor tube if the space between the joists is filled by insulation? Is it better to get a warm roof if you don’t have problems with the neighbours?
Good video Roger. I do a bit of GRP roofing works but our boss gets us to put 100mm on top and 50mm to the under side. When I asked about vapour barrier he said with this system you don't need one.
Same principles apply - but there you're keeping the heat out. Check out Matt Risinger's channel as he's rebuilding his home in Austin and super insulated it. There was recent news about the world's most reflective white paint that has the same effect as air conditioning when a house is externally painted with it - could be revolutionary if it comes to marked. Simple answer is a cold roof would be better there as you can use the top of the roof as a rain screen and break a lot of direct thermal transfer between the roof and internal ceiling.
To be honest if you have air con then the vapour is travelling from outside to in. The whole thing is fraught because humidity is higher in the summer. There are some people who say that you should not have a vapour barrier in those situations and just let the moisture drift through
I understand this, but, Why dont you put the vapour barrier down before the fist osb. Is it just because they become damaged and its difficult to install. May be i do not understand it after all.
I am currently doing a garage conversion. Turning it into a salon for my wife it’s having 3/4 inch ply boards on roof 2 layers of under felt and mineral felt for top layer. The under side of the roof (the structure) is all 2x2 timber which leaves me with 50mm void. What would you recommend just add no insulation them add insulated plaster bored maybe ? Thanks
Hmm. Well, when we build ships we pack the steel against with rockwool hard up. The main issue is stopping the air getting to the steel - or wood - to condense. Given that we have humidity levels at near 100% and a temperature difference of sometimes 90C between machinery rooms and the sea it works fine. I did a roof 12 years ago and used 100mm of Celotex foil backed and sealed it solid so no vapour could reach the OSB and then another 100mm of Rockwool to add even more insulation and fire proofing. No issues at all. As for the plasterboard - I used foil backed and fitted sealed downlighters.
Is cross ventilation required for a office outbuilding as its low occupancy, as long as you have good vapour barrier. My office room build has a steel cross beam.
Apparently in the states they are specifying tissue based pir board insulation when used with a separate vapour barrier. All to do only allowing one vapour barrier. It's constantly changing.
Can you help? Is there any way for me to increase the R-Value of the roof from inside, without removing the rubber and working from top down???? Details: I live in a 1000 sq. ft. ranch house built in 1960. The roof has about a 15 degree slope. When I pull down a piece of ceiling drywall in the open living room, I see a 2x8 rafter with 5 ½ inches of faced batt insulation. Then the roof deck, ½ insulation board and then a white rubber covering on top. Looks like it was all quality done at the time. ---- The 2-3 inch gap between the top of the insulation and the bottom of the deck allows it to breath, with vented soffit. Thank you if you have any ideas, as my web research has been unfruitful.
With a cold rood. Could you not put a vapour barrier on the inside of the insulation? In my head that would seem that no moisture would even get to the outside of the insulation/dew point. Therefore, that would make the void and all the ventilation aspects redundant? I don't know if this would work but the implication from a warm roof implies that it could. The only potential issue I see is when installing the plasterboard the screw for attaching are going to pierce the vapour barrier which isn't ideal but I'm sure there would be a way to avoid or mitigate that, if it even is an issue considering the piercing would be filled by the width of the screw.
It's time to thank you. I've used your videos to build 2 walls, insulate my garage and tank a wet room. You explain things so well that I understand and can question things in my head. Insulated summer house / office is next which I'm hopping to start in the next month or two. I still bring in the pro's where needed, but understanding what is going on really helps and I think just raises the standards as a whole. Thank you!
Thank you for the message on this fine sunny Easter Sunday.
Hi lads, You know what, I am level 6 NVQ (not very qualified) site manager, level 3 carpenter and joiner, and intermediate qualifications in Brick laying, plumbing and plastering, (also a fully qualified Locksmith), with 33 years of mud on boots experience, I've forgotten more than most people actually know, but...... I literally LOVE your videos and pod casts, (only found you the other day, so alot of catching up to do),very informative entertaining AND engaging, even if you are shandy drinking Southerners. Keep up the awesome work 👌
Nige
Never touch shandy or larger. Give me a pint of best bitter any day. Unfortunately the number of pubs now serving ale are fewer than they used to be.
Going to be doing a garage to office conversation soon, needed this lessen. Thanks Roger
Also need a spelling lesson
@@NordenEngineering lesson. Sorry teacher.
@@vinnysurti* conversion
😂👍✊
crazy how the neighbours would be annoyed if the roof was 120mm higher... I would NEVER EVER EVER be that kind of neighbour. Why would they object to 120mm? What difference will 120mm make to them? Crazy! Anyway, thanks for the video! Very helpful
San Francisco, California, homeowners should take note of Roger's sage advice!
Such a unique breadth and depth of knowledge from Roger, we are lucky that he is willing to share it with us. Thank you Roger! 🙏
Nice of you to say so, we try.
so unique to the extend that he redefines the dew point at 3:50. He even draws an arrow pointing at the dew
Dom, so easy to binge watch your content. Well done to you and Dan. The editing is superb.
Jamie
Thank you so much...the time and dedication that you put into this video was wall appreciated. You helped answer so many questions I had.
After watching countless videos on youtube once again Roger hits the nail on the head and makes it perfectly understandable. cheers marra
Such a sensible informative gentleman and useful advice to avoid moisture issues on garage roof I’m insulting 👍. Simply explained Tx
Great vid Roger, nice and simply explained.
Excellent as always!
Very clear and helpful, nice video Rodger! We're always doing these sort of extensions and when the joiner talks to me about hot and cold roofs I'm always bamboozled 😂😂 look forward to see the next video on this project bud!🍻👍
Great video explaining in very clear way the difference between cold and warm roofs
Never really thought about the subject before Roger but in many big old houses they had cellar and attic spaces with air grills below the floor space for the air to circulate. I was lucky when we bought our 300 year old 3 bedroom cob cottage with a thatched roof (cold roof).
The 3 foot thick cob walls are build off a rubblestone plinth with no foundations or guttering, the ground is hard clay and stone.
There was bad damp when I moved in because the walls were cement rendered and it had been a holiday home for about 15 years which had caused all the damp issues and rotted the timbers on the damp side of the house because I have a hill behind the house whose gable end faces into the hill and in front of that there is a 25 foot deep stone lined well, the water line is about 4 feet below ground, never higher and is only low during summer. Since I put in a French drain along the back side of the house and lime rendered the place we've have no more damp issues.
The first floor ceiling is wooden lath & plaster (the walls are reed and plaster), a thick layer of haired course lime mortar and a single layer of thick top coat white lime skim 5 to 6ml thick. Another property of lime walls is they absorb moisture and CO2 and give you better acoustics than cement or gypsum, a friend in nearby Stogursey has plastered his internal walls with clay which has even more amazing qualities.
It can be expensive to do but, done well it should last a life time whereas modern builds are designed for about a 40 year life, even a strawbale, single floor structure would last a 100 years.
Above this ceiling line is the triangular shaped attic where, between the joists you can see the back of the ceiling and the folded nibs of that 200 year old, haired lime putty mortar and on top of that, between the joists are a few rolls of Rockwool insulation with a 5 foot air space before you see the underside of the straw roof. It's relatively dry. In some of the bigger houses they'd put a thick layer of tamped soil and sand which would be good for the sound proofing and insulation properties.
During the night, summer and winter, we sleep with our bedroom window open and during the day, unless somebody is home, everything is shut up.
Up the road is an equally old property which has a double-Roman, clay tiled roof, when I climbed up to look there was no roofing felt and it too was dry.
As you said on one of your rants, there's no point having an air-sourced heat pump, if the home isn't well insulated inside.
I'm house rich and cash poor and can't afford one but I would like a ground-sourced heat pipe, they do work, I would also like some solar panels please.
It would help the planet if we all had solar, wind and thermal generating capabilities with storage capacity for any excess power with every home as standard and, if you have a small garden, a compost heap is great for all your organic waste. Ours is barely large enough for the herring bone pipe to the septic tank which is emptied every year (£250) and is cheaper than the mains sewage bill I'm told.
We've go no government grants, none available, or help with lower VAT for sustainable buildings, and it was bought to be our family home and so long as it continues to be repaired with like for like materials it should last another 300 years.
keep up your interesting topic please, it's healthy when we can all rant.
* Star Wars theme plays *
@@DinckelburgVery clever 😂
Thanks so much, just about to build a warm roof for my conservatory. Amazing to see how literally none of these "kits" do not include the ventilation for the cold roof.
Great explanation. Thank you!
Built an extension on my house under the new cold roof insulation regulations, resulting in a permanently cold room, took the roof off 18 months later and made it a warm roof, now have a lovely warm room.
The clue is in the name I suppose
You are the best! Thank you for the explaining.
Good explanation for people that don't understand the difference. 1 thing that would be better for ventilating the dead spots created by the lantern would be to counter batten the roof the opposite direction of the joist to create a cross flow ventilation throughout the whole roof. Although you increase the deck height by 25mm you get rid of the need for unsightly mushroom vents everywhere 👍
Exactly!
ALso have to consider how much height the shrooms add and what they look like...
I did wonder when mushrooms kept being mentioned how the neighbours concerned about the height of the roof would like the mass of mushrooms there'll be instead.
A UA-cam channel called Steve roofer shows a good ventilation detail on the flashing, well worth consideration
We know that channel well and he is great. We have used that ventilation detail in the past but, as you may see it would have come up above the parapet wall and upset the neighbour
@@SkillBuilder ...ahhh the poor neighbour, can i picture a forage on the roof, Monty Python style?
Surely you had plans which the neighbours could have objected to before the build commenced?
@@georgeturner6648
Orangery are permitted developments, within certain parameters.
Then it's permission from the neighbors.
They may of had permission, but then the neighbors changed their mind, and to stop the ball ache of courts and council. Which you may or may not win. Especially if you lose you have to pull it down.
Sometimes it's easier in the long run to just go to what's permitted without neighbors consent.
Perfect timing. Will be starting on a garage conversion soon and need a new roof. Exactly what I needed. Warm roof it is. Cheers
It really is the best option, I am very uncomfortable with this arrangement
@@SkillBuilder
Whereas in my industry (hard metal roofing) we hate warm roofs because they fail more than cold roofs.
Thanks for this. Definitely the clearest and most easy to understand explanation of a cold roof and warm roof on UA-cam.
Nicely done, I did a little office using warm deck. I stopped the joists at the wall plate, but extended the OSB and 4 inch insulation beyond to create a 200mm overhang. Then sandwiched the edge with 2x4 so I could hold it all together. I only did this to avoid creating an ugly thick fascia that was 300+ tall, instead there's a neat 150mm fascia with the gut attached.
Hi Chris
Nice to see you back. We also do that trick to reduce the fascia height
I wish all tradesmen were like you Roger.
Great video Roger explaining the key differences between a warm and cold deck for a flat roof. My comment is on a warm deck. Like a lot of information out there the principle is illustrated by a cross section and details of the layered structure above the joists. For the void between the joists it is always made clear that there must be no insulation between the joists as this will lead to the rising moist air through the ceiling being cooled by the insulation and effectively producing a cold deck but with no ventilation.
It would be really good if you could explain the detail to produce the sealing around the perimeter of the void space when an existing old flat roof is being replaced. The joists are above the wall and open to the air when the original fascia is removed. Your video includes at 1:35 'All this area here [between the joists] is warm. It is within the heated area of the house' which is fundamental. I have only found one set of videos by @SteveRoofer describing and illustrating the inclusion of insulation around the perimeter between the existing wall and the underside of the new deck. The principle is clear in CNCD-053. With just a new fascia board and no perimeter insulation the air in the void between the joists will experience some cooling defeating the basic assumption and potentially achieving the worst of all worlds. The wall cavity will be within the void space and this will also add to the cooling effect depending on the quality of the cavity insulation. This is all obvious to me after not much thought but seems to not be fully grasped by the roofing industry when you ask for a quote and for a description of the planned work even by reputable companies.
Thanks, excellent video!
Simple answer - badly installed cold roofs are bloody freezing when the builder who owned your house doesn't air seal between the Kingspan slabs and the joists. It's basically external temperature just above the plasterboard.... 🥶
Also just found out he didn't stick a vapour barrier above the plasterboard either. 🤦♂️🤦♀️😤
Brilliant explanation Roger
Really informative video, Roger.
Excellent job great explanation 👍
What an excellent explanation. Thank you.
I did my flat roof on my lounge 15 years ago. Plaster board, fibreglass, OSB and felt. No sweating, no damp, no problems. Still as good as the day I did it. I can't help but think that a lot of this is snake oil and more money for the men in suits. Great explanation Roger, as always.
My friends house lasted four years due to moisture building up in an unventilated roof space. It is happening all over the place and it is largely due to modern building techniques.
Look at the thermal values of celotex vs old fashoned inulation rolls.
Thank you for a very informative and well delivered explanation. Keep up the good work.
Interesting stuff Rog , what a massive pain in the area for
5 “ though ! 😳.
Look forward to the build 🧱👍🏽
This channel is a gold mine of knowledge 👍👍👍 Thanks and thank you for your passion
Excellent video, thank you
Highly interesting....more demonstrations would be very much appreciated...thanks
The whole video will show plenty of detail but it is work in progress
Excellent stuff. I'll now change what I was going to do with the roof of my new dormer.
Ever thought about fitting cross battens running the opposite way to the joists,this creates a continuous air flow of 20mm. No need for mushroom vent. As long as you have.front and rear air soffit/ facia and abutment vents.
Can also set the circular saw to 20mm and cut a notch out the joists. Obviously it slightly weakens the joists but we usually over engineer flat roofs anyway! Iv done it that way before and was really fast and much better than drilling holes as they get clogged easily
Always counterbatten cold roofs for cross flow.job done
@@chriscoulson7684 You're not a structural engineer are you! Notching out the top or bottom of a joist doesn't 'slightly weaken' it - it is the worst place to cut it. The bottom is in tension
and the top is in compression - somewhere in the middle on the neutral axis there is no stress.
Excellent info, thanks 👍🏻
Excellent stuff roger, as a building control surveyor the most common mistake is a warm roof with no decking and VCL below. Happens all the time! Every PIR supplier will ask for an 18mm deck with the VCL
Thanks James. What would you accept as a VCL? Is 1000 guage polythene suitable? I only ask because the dedicated VCL products cost a fortune.
Thank you very much for sharing, Master!
Brilliant, thanks, really clear explanation.
Thanks Roger, excellent explanation to a bit of a head scratcher. Am going to replace my old plastic roof on my conservatory and had been trying to weigh up the best way of tackling it but you just explained it in less than 10 minutes!
A very informative video. Thanks for sharing
Thank you for sharing that knowledge. In NZ we build a lean to extension with a mono-pitch roof. Plaster board 200mm joists, vapour barrier then corrugated Iron. The Insulation is Pink Batts skillion roof insulation. The insulation had to be specific due to the insulation loft limitation giving allowance for at least a 20mm gap - I now further appreciate what that gap is for. More so it gets me to thinking about flashings and how well they can release water on the inside without letting water in. Hopefully the building codes we built to are correct.
Come see the uk new builds a meter of installation double glazed windows its like being trapped in a oven. ive not closed mt windows all year ... on the inside 30 mm pipes for the plumbing 15 mins to refill a toilet.. but they are alot cheaper than million dollar nz .
@@JONO3679 Sounds like a pressure issue or restricting washers to the toilet water supply? Many 'eco' toilets these days use too little water which can cause more issues - blockages - than having a decent flush volume.
Awesome explanation, Thank you. I am considering this for a project and wanted to understand it.
My thanks to Skill Builder and Roger - now all i need to know about warm and cold flat roofs. Infact my new extension Surrey side of Gatwick a semi-detached and all flats are cold. my new extension will be warm and work to change my current flat roofs to warm but will leave attached neighbours as is. with some magic (in the drawings) for the builder !!
Great as always Rodger. I have a 15-year-old log cabin. It's perfect inside but a bit dated on the outside. I spend around £100 per year maintaining it as well as the cost of heating. I am about to insulate it on the outside all around and have the products but not 100% sure of which way to have the insulation, membrane etc. I don't want to insulate the inside as I like my LOG cabin. I have 60mm Kingspan sheets (got them cheap so can't change) a breathable membrane, PVC cladding for the walls and box profile sheets for the roof. I was intending to stitch the membrane onto the outside walls then Kingspan held with 2"x1" battens and the pvc cladding onto this. There would be the 1" air gap behind the cladding vented at the top and bottom with mesh to stop wasps etc. The roof is 20mm t&g pine and is felted. The felt needs replacing so was intending on removing this stitch the breathable membrane on top, Kingspan, 15mm OSB then the box profile sheets directly on top. Do I need to change the membrane for a vapour barrier? If so where does it go? Do I need an air gap roof or walls? Any advice would be appreciated as I'm getting conflicting messages on other forums, everybody seems to be an expert
Great videos! I've tried reading most comments so apologies if it's been asked before..
I'm currently starting a new build with a pitched roof. Strangely enough when you search for a warm roof, most videos, info etc. are in the context of a flat roof.
Not a great deal of warm roof examples of a pitched although I have seen a handful of insulation companies i.e Kingspan, Tyvek with demo videos and illustrations of this exact setup, though they leave a lot to be questioned, they do show this is a practised method.
My main concern really is only a problem when you have a pitch and that is the limited shear strength of the very long screws/insulation fixings that have to sandwich the battens to the rafters with this approx. 100mm of soft insulation board in between that provides no stability to these screws. I hope this makes sense, it's a question I haven't quite seen addressed before, thank you for your time!
Hi Michael
You are right to say the focus is on flat roofs but a pitched warm roof is fundamentally the same.
The best way to approach it is to counterbatten on top of the insulation in line with the rafters. You can buy stainless steel helical fixings. They are twisted so that stops them bending and they won't pull out.
thorhelical.com/product/warm-roof-fixings/
Once you have the counter batten fixed you just batten out the roof in the same way you would on a cold roof.
Thank you so much for this advice, I actually introduced a joiner to these fixings who was quite impressed!
So well explained!
I think i would have gone a cross the 9x2s with tile batten so the whole roof is connected and reduce the number of roof vents. Not only is all them mushroom vents going to cost a lot especially as they have to be built into the roof covering, they will look facking ugly.
Good vid Roger 👍
Hi Tony
Good idea but we had the deck down and we were going with the warm roof so we didn't want to rip it all up and counter batten. Also the counter batten doesn't give enough cross ventilation on its own. The whole thing is a ball ache and it is all down to a neighbour who said it was O.K and then said it wasn't.
@@SkillBuilder Remember- never ask the question if you don't want the answer. If you have permission for the higher warm roof, go with it, and don't ask the neighbours for their opinion
@@rossbuchanan7632 ...building regs? It sounded to me like there was a veiled mention of the fact that some arch holes can be nay bores. i for one wouldn't like to challenge a regulatíon and have to rip off the roof and then live with the people who opposed me in court. Ridiculous though, that it's a matter of less than a foot.
@@SkillBuilder Had loads of grief with neighbours. Not about height, they just don't like seeing people get on! Can't win, don't even try. Do what's best for you! Just make sure you stay within your rights. They will complain !
@@danieljones741
Tends to be, there's max heights your allowed with no permission, anymore you need to consult neighbors.
More videos like this Roger 👌🏼
the best build channel imo
Thank you, we try hard
Worthwhile advice!
I have a large flat roof over a kitchen, 75mm fibreglass between the joist with cross ventilation from soffit into the pitched roof void. Its 45 years old and its fine - the fibreglass gets a bit damp in the winter but it always drys out quickly enough.
The original chipboard deck failed after 10 years so I re-boarded it with marine ply and had high performance polyester felt laid on top. 35 years later still no leaks.
Sometimes low tech works just fine.
lol, perhaps should have told the neighbor "We can avoid putting unsightly shrooms on the roof, if we just build it a little higher!" ;-)
Fantastic just what I needed ❤
Very interesting subject. Most people wouldn't give it a second thought. But it's important you know in case of dry or wet rot. Thanks rodger👍👍
Warm or cold roof, always avoid moist getting in the construction from the warm side of the construction, Make a 100% damp sealing above the plaster board.
This is very useful :) I'm converting my garage to a room and I'll speak to the builder what he plans to do with the moisture issue :D
I'm surprised the neighbour is even aware of the 'options'. This is what was granted permission, these are the plans and dimensions, and this is what is getting built!
When I put up my extension , It was a cold roof because of the design I wanted. I used foil back pb and foil taped all the underside of the joists to the foilbacked Kingspan so there could be very little chance of any moist air penetrating. Redbrick vents to the front and proprietary vent escape vents to the rear. Hmmmm, forgot about the dead spaces though, gulp ! That said, ten years in and no problems as yet.
hi
great explanation
bang to the point
The neighbours annoyance at the hight of the orangery should have been noted in the permission stage before the project started. Once permission is granted there's nothing they can do
Is it normal on the roof to fit 18mm plywood then osb on top before the grp . Or is this overkill and trying to rectify a problem with the plywood , thanks
learned a lot. That’s why I love this channel. Keep em comin Roger.
I am about to do this, bloody gold.
I built a garage extension where I didn’t have the height for a warm roof or the joist depth to achieve the required R-Value with venting, so I used Closed Cell Spray Foam. It is allowable under the Canadian Building Code for use in unvented roofs because it acts as a vapour barrier. Pricey though.
That would never pass regulations in the uk. It doesn’t allow anything to breathe! The uk is far too damp for that type of insulation!
Great teacher, thx.
Learn something new everytime, thank you
Great explanation
food for thought. i have two flat roof extensions. both had no air space, both rotted. hopefully the roofer done it right this time. i have edpm roof covers on now.
Jeez, that's interesting I did a substantial repair job on my roof myself (Cold roof) I did my research and I knew the principle of the through flow of air and I didn't really do a great deal of work so I assumed the existing structure would work in the way it was designed. I had serious condensation problem. The previous owner - my father in law had put fibre glass in between the joists laying directly on top of the ceiling plaster board. My analysis of the problem was the moisture was getting through the boarding, and then hitting the cold air beneath the tiles the condensation accumulating under the tiles and dripping into the fibre glass and eventually making contact with the plaster board. I felt that the fibreglass that was filling almost all of the cavity and was reducing the air-flow and replaced that with GRP. That then left a good gap for the air flow. Not had any problems since (4-5 years now) so assumed I'd done a decent job. I'm going to check that out when the weathers good. PS it's a very shallow angled roof 25 degrees. Good vid.
Well that’s another new thing I have learned from you, Thankyou.
Don't forget there is an exam coming up at the end of term so make notes.
Great vid.. very informative
Roger for me cold is always the way to go as long as it’s vented properly, around the Sky light/ Lantern you can do a vented upstand where you cut the ply short 25mm and run 50x25 batten vertical and leave the upstand ply 25mm short at the top thus creating enough draw for the air to move, it’s what we always do.
If you have the height available, warm roof is so much better.
@@TurinTuramber how many have you had to redo?
@@denty32 Zero of either. Cold roof needs more work if done correctly and down lights can be a pain. Much easier running out full sheets of materials from above deck. The extra height can look unsightly, that is true. Don't get me wrong, if it works it works.
@@TurinTuramber every flat roof / low pitched roof I get called out to inspect is 99% a warm roof with poorly fitted Vcl. Every one thinks warm roofs are easy to install until it goes wrong. It’s normally a SVP or flue that didn’t get fitted at the time of installation.
@@denty32 On a clear roof like an outbuilding there aren't really any interruptions so goes down super easy. Some roofs are busier than others. Also cold roofs thermal bridge like mad, Roger didn't mention that I think.
You could simply cross batten between the joists and the OSB to get your cross ventilation, definitely cuts down on mushroom vents
I built a flat roof with cross battens. It was a continuous problem with the boards moving about and cracking the waterproof layers.
A butyl membrane would have been ok but the felt I used was a nightmare
I seriously regretted not nailing the boards solid and using mushroom vents.
Roger, firstly great explanation.
Can you place a link to the grp mushrooms that you would recommend between the joists, and also the upstand ventilation product you also mentioned please.
You talk about the warm side sand cold side of the insulation. Where are you located? What if we live somewhere that uses heat half the year and air conditioning half the year? What's the cold side?
The GRP mushrooms cost the guts of 70 euro a piece here in ireland. We tend to use them sparingly.
brilliant info - would be nice to see a video showing what it looks like
It will happen but we are in the middle of it right now
So rather than seeing a 5 inch higher, nice flat roof - the neighbours can look at a huge number of tiny chimneys. Silly sausages
Yep!
Mouth breathers as AvE likes to refer to.
I was thinking exactly the same. They're moaning about an extra 12 cm in height. Unbelievable!
Surely the mushroom ventilators are about the same height as the extra thickness would have been anyway!
@@timt3813 was wondering that. Can they not complain about that also?
I loved your class but how can I work out around the stairs
Great video Roger.
I wonder why you didn’t opt for counter batten over the top to negate the need for the GRP mushroom vents? Just pitched a lean to roof and I’ve counter battened and put vented soffit on all three sides.
We would have counter battened but the deck was down by the time the change of plan came.
Just seen this after commenting myself about cross flow ventilation. Would of been a much better way but rach to there own and we all are still learning
I used the 25mm multilayer foil insulation for a warm roof, supposedly equivalent to 225mm of fibre insulation, but adds no more than 40mm with the counter battens. It all seemed to work well.
I'm planning an orangery type extension on the house I'm buying.
Where do you put the electrics/extractor tube if the space between the joists is filled by insulation? Is it better to get a warm roof if you don’t have problems with the neighbours?
Good video Roger. I do a bit of GRP roofing works but our boss gets us to put 100mm on top and 50mm to the under side. When I asked about vapour barrier he said with this system you don't need one.
I think you are talking about a hybrid roof there and the insulation on the underside is the vapour barrier. It will have to be well sealed.
What would be the best way to insulate if the heat were the other way round. i.e. an air-conditioned house in a hot humid climate?
Same principles apply - but there you're keeping the heat out. Check out Matt Risinger's channel as he's rebuilding his home in Austin and super insulated it.
There was recent news about the world's most reflective white paint that has the same effect as air conditioning when a house is externally painted with it - could be revolutionary if it comes to marked.
Simple answer is a cold roof would be better there as you can use the top of the roof as a rain screen and break a lot of direct thermal transfer between the roof and internal ceiling.
To be honest if you have air con then the vapour is travelling from outside to in. The whole thing is fraught because humidity is higher in the summer. There are some people who say that you should not have a vapour barrier in those situations and just let the moisture drift through
I understand this, but, Why dont you put the vapour barrier down before the fist osb. Is it just because they become damaged and its difficult to install. May be i do not understand it after all.
great explanation.
I am currently doing a garage conversion. Turning it into a salon for my wife it’s having 3/4 inch ply boards on roof 2 layers of under felt and mineral felt for top layer. The under side of the roof (the structure) is all 2x2 timber which leaves me with 50mm void. What would you recommend just add no insulation them add insulated plaster bored maybe ? Thanks
Interesting. Do plaster and lathe ceilings also let moisture up to the roof?
yes
Hmm. Well, when we build ships we pack the steel against with rockwool hard up. The main issue is stopping the air getting to the steel - or wood - to condense. Given that we have humidity levels at near 100% and a temperature difference of sometimes 90C between machinery rooms and the sea it works fine. I did a roof 12 years ago and used 100mm of Celotex foil backed and sealed it solid so no vapour could reach the OSB and then another 100mm of Rockwool to add even more insulation and fire proofing. No issues at all. As for the plasterboard - I used foil backed and fitted sealed downlighters.
So the neighbours would rather see a mushroom field !
Is cross ventilation required for a office outbuilding as its low occupancy, as long as you have good vapour barrier. My office room build has a steel cross beam.
Good explanation.
Apparently in the states they are specifying tissue based pir board insulation when used with a separate vapour barrier. All to do only allowing one vapour barrier. It's constantly changing.
Can you help? Is there any way for me to increase the R-Value of the roof from inside, without removing the rubber and working from top down???? Details: I live in a 1000 sq. ft. ranch house built in 1960. The roof has about a 15 degree slope. When I pull down a piece of ceiling drywall in the open living room, I see a 2x8 rafter with 5 ½ inches of faced batt insulation. Then the roof deck, ½ insulation board and then a white rubber covering on top. Looks like it was all quality done at the time. ---- The 2-3 inch gap between the top of the insulation and the bottom of the deck allows it to breath, with vented soffit. Thank you if you have any ideas, as my web research has been unfruitful.
I’m installing warm roof on my extension, mainly to annoy my neighbour. Didn’t even give them the option 🤣
With a cold rood. Could you not put a vapour barrier on the inside of the insulation?
In my head that would seem that no moisture would even get to the outside of the insulation/dew point. Therefore, that would make the void and all the ventilation aspects redundant?
I don't know if this would work but the implication from a warm roof implies that it could. The only potential issue I see is when installing the plasterboard the screw for attaching are going to pierce the vapour barrier which isn't ideal but I'm sure there would be a way to avoid or mitigate that, if it even is an issue considering the piercing would be filled by the width of the screw.