Stop Roof Damage: Insulation Secrets Revealed!
ฝัง
- เผยแพร่เมื่อ 3 ต.ค. 2024
- Steven Dickinson
London Flat Roofing
07802300099
info@londonflatroofing.co.uk
During my roof inspections, a common issue I come across is that roofers often neglect to properly "tuck in the roof." What does this mean? It means they haven't correctly installed the insulation behind the fascia board. In warm roof systems, the insulation doesn't run between the joists; its installed over the joists the gap between the joists remains open and is at the same temperature as the room below.
To understand this better, think about your wooden table and chairs. Do they ever rot? No, because they are in a controlled environment. In a flat roof, the air vapour control layer distinguishes between the internal and external parts of the building. Everything above the air vapour control layer is considered external, and everything below is internal.
For effective insulation, the insulation above the air vapour control layer should extend across the roof and connect to the next thermal element. In other words, it should be tucked in all the way around the edges and joined to the walls surrounding the warm roof. This ensures complete encapsulation within the insulation, providing warmth.
When I do roof surveys, whether on new roofs or for people experiencing issues with their roofers, I often find that no insulation has been added around the fascia area. This oversight allows cold air and moisture to enter the living room below.
Remember, just because you have a ceiling doesn't mean the space above is not internal in a warm roof system It is. And proper insulation is key to keeping it warm and moisture-free.
www.londonflatr...
Steven Dickinson
London Flat Roofing
07802300099
info@londonflatroofing.co.uk
@steveroofer
#londonflatroofing
#londonroofsurveyor
#steveroofer
Storm damaged roofs in London
Roof surveys
Roof surveyor
London Roof surveys and inspections
Roof consultancy
Roof consultancy and roof condition reports
Domestic roof survey
Flat roof condition report
Independent roof surveyor
Leak detection roofing
I phoned Steve and he gave me some great advice on my roof for my garden house. It was really helpful to speak to an expert in this area. Many thanks Steve 👍
Excellent video. Great detail and explanation. You should be a construction teacher. Learned a great deal from watching this. Thank you.
Only just come across this, I’m a builder myself, it’s good to see someone else addressing this issue of a forgotten or missed insulation detail. I can’t understand why it’s never picked up by BCO’s. I’ve recently raised the roof height of my kitchen extension that someone else built, I think Stevie Wonder inspected it originally. Anyway, although not picked up by the Bco, I insulate all my joist void ends so I hopefully don’t get any issues. Well explained sir.
😅
Excellent video and information, finally someone who knows what there talking about, I have learnt a lot today from your video.
Thanks for making this video, you have helped many a diy'er here and maybe some professionals too ;-)))
Exactly the information I need on Warm Roof fascia insulation. Many thanks.
Many thanks for uploading this. Typical that I viewed it six months after redoing my flat roof and not taking into account several of the points you raised. Ah well, it will give me an excuse to do it again in a few years :-)
Architect here! Great informative video. Thank you.
Great informational videos. As a roofer myself I found this and more of the videos very interesting. The company I work for would do well to watch these and pay attention to some of the details you bring to point
All of your videos are most informative and well presented. Great work!
:-)
Very good Steven ,very well explained, you are correct you pointed out some details that I over looked, thanh you on an excellent video, Tony from Dublin.
Thanks the information i'm getting is moving all the time we are now being told not to use any timber above the VCL?
Excellent detail and info. Many thanks Steve !
Thanks for an informative video. As a client about to embark on such a project, you have provided guidance that I can use to ensure the roof goes on properly. Warm roof for me!
Glad it was helpful!
Thanks Steve, great concise explanation.
Ok thanks
Very well explained with good 3d illustration.
Good explanatory video. I went with the cold roof option a few years ago because my dad is a plasterer so we pulled the ceiling down and insulated between joists and added a continuous sheet under joists above the plaster board. Made it much warmer but..... the screws holding the board and insulation up obviously go into some cold joists. What I have found (only when I light my wood stove strangely) after a few months I have small dark shadow marks over the heads of the screw, which I think are probably condensation marks where the warmer air is condensing on a cold screw head. It's the only thing I can think of. Be interested to know if you've ever seen this or something similar before.
It is. It's the same reason plasterboard mushrooms can be bought with plastic covers. If the screw heads were covered you wouldn't have that issue.
Hi Steve, great videos! Hoping you are still answering questions, I've tried reading most but 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 and I understand you specialise in flat roofs but it's a question I haven't quite seen addressed before, thank you for your time!
No not many people do warm-pitched roofs because of the buildup, given that I have never seen one but I know that if you do one, you can have problems with the hole lots sliding down and somewhere along th the line, i did see that they put the fixings in at an angle but I dont know where I saw that
Excellent video….thank you for posting this…BRILLIANT !
Not down anything below the insulation is a warm space, above is a cold space you vent the cold space above the ventilation making sure there is a flow of air between every joist, normally achieved by running a continues vent at the gutter board and under the flashing to a wall.
Smashing video. Thank you very much. Just what I was looking for
Quality video. Very helpful.
Just found this and I am so glad as this is what I am doing. Gone a bit madder than your solution and using Bosig Phonotherm under steels.
Sounds interesting. Send over some photos
@@SteveRoofer Many thanks - sent to info@
Very good explanation - thanks for sharing.
Warm roof also gives you space for your downlights.
I had a vaulted roof extension put in a few years ago. They used the rock wood between rafters, then space blanket with 25mm battens for the plasterboard. Downlights had cuts through the blanket to allow them to fit😢
🤦
that's not a bad specification, but you can't cut through the space blanket
I must send you all my pictures of my failing flat roof 🏋️♀️🤺👍🤗
Great job. Very informative.
Steve, or someone who knows the answer, please clarify for me one question.
It is recommended to put insulation behind the fascia board so that the insulation in the cavity and above the joists is continuous. I understand this bit and makes perfect sense.
The question relates to the vapour barrier. There is vapour barrier above the joists on top of the OSB/Plywood decking right under the insulation boards to prevent vapour to get to the highest cold spot of the flat roof structure. Horizontal layers: EPDM/etc. -> OSB -> insulation -> VAPOUR BARRIER -> OSB/Ply -> space between joists)
Here comes the question:
- Using the same logic, shouldn't there be a vapour barrier between the insulation behind the fascia board on the one side and the same space between the joists on the other side (vertical layers: fascia board -> insulation as per the video above -> ??? VAPOUR BARRIER ??? -> space between joists)?
- If no vapour barrier (VB) , can't the vapour still get to the fascia board, the cold spot?
- If VB is needed above the joists then why is it not needed here?
- If VB is not need here then why is it needed above the joists at all?
Sorry for putting this simple question in a complicated way.
Please advise.
Joined up thinking in the building trade. It will never happen. As a roofer, I'm only asked to look at the roof and not at the rest of the building! Madness as whatever I do to the roof will have a knock-on effect on the rest of the building. Unless you are building the walls and the roof all calculations given seen to assume the at the rest of the walls and building are correct. Realistically an old property being renovated bit by bit is unhealthy until it has been completed. Update the roof to a new specification and all other elements of the building are now week. A new warm roof won't breath so that moister has to go somewhere and it goes to the next weakest element of the building. So the answer to your question when you insulate between the joists above a wall assume the vapour control should be as good as the walls or better. Unless the wall is new, I believe that by fitting and foaming insulation tightly between the joists, this forms a VCL that is as good or better than the old wall. Everybody gets hung up on the VCL, and that's good. Fundamentally stopping the movement of air is more important as it carries way more moisture into a roof that what gets stoped by the VCL. All of the above is my opinion as from my experience all professional bodys have dropped the ball.
Would be great to get some information on why this isn’t required in a new build. How would those be constructed differently to avoid the fascia thermally bridging please?
To get the correct U value a calculation will have to be made but generally speaking 100 to 130mm will normally bring the thermal property to the correct level, the more insulation you put on the roof the better. In Europe they are using 300mm
Thanks for the video; how do you go about the detailing of the moisture barrier covering the vertical insulation? surely it would have to be cut to fix between the joists? cheers.
Excellent, Thanks for sharing.
Well done, another great video. Thanks.
Excellent video 8 years on. Quick questions if you are still answering questions. In garden room where height is limited and a cold roof is used AND it is vented as you suggest, how do you overcome these 2 problems?
1. The roof rafters may have noggins which means ventilation is blocked
2. When in stalling down lighters (LED spot lamps, GU10) you have to cut a hole in the insulation and vapour barrier which will then expose the top of the fitting to the ventilated area which now can cool the hole around the light
Many thanks
Good question and this one comes up all the time when talking about cold flat roofs first you must have a ventilation gap above the installation and the installation must be on top of the plasterboard and there must be a vapour barrier Under the insolation and it must be completely airtight running the full width and breadth of the ceiling and ceiling to the walls so that no air can penetrate up if you have noggins cut holes in them make sure air can move across the noggin from one area to the other area you do not want to have any Dead air spaces. Theoretically you could cut your lights into this as long as you make a box for the light to sit in that is airtight and insulated all the way round however that does prove extremely hard to do and not successful so don't use down lighters in a cold roof
What a fantastic informative video !!👍
Very useful video desribing a problem I realised I had just this week. Below my warm roof extension is a living room, and inside the house is a dinning room. They are basically the same room, but half is an extension. I noted that there is a 2c difference in the heat of these two halves. The extension ceiling is cold, the house celing is warm. I checked the downlighters, and sure enough theere was a very cold blast of air pouring in the room below. The ceiling itself is very cold. It did not take much to deduce that this is because the thermal integrity of my roof fails because of the soffite board, an uuninsulated 20mm board! Your videao was very useful in providing another veiw, concuring with my veiw. Unfortunetly you did not say HOW to remidy the situation. If I remove the facia board and put foam board or fibre insulation between the joists, would i have a problem with no ventilation? My internal down lights do provide direct air into the void, would this be sufficient. Any comment would be appreciated
Just go around the perimeter in between all the joists and backfill with insulation as high quality as you can so use PIR insulation and foam it into place. Airtightness is what you're looking for.
Thank you Steven, this was a very helpful video.
No problems glad it helped
You still didn't explain the detail of how you'd do the insulation for that application in the warm roof besides pointing with the cursor(?)
What it seems like, since there's no ventilation is you insulate the overhang, and probably overhang it inside to the house as well..
Where are the pictures of the rotted roofs you mentioned? :P
Very nicely explained , well done !!
What interests me first and foremost is the extraction and inflows of air....if we have warm moisture laden air inside and/or moisture laden air outside....it's the practical movement of this air that's important...and that for me is the place to start
Well, you know, this is something that I have been pointing out that sometimes with bringing in air that is more moisture laden than the air that we are replacing it with. By stopping the energy flow from inside to outside means that the drying potential has been taken away from a roof void, leaving that roof void less opportunity to dry out !
Very informative video and just what I am trying to design out of our extension, thank you for taking the time to do this. On a new warm roof would you recommend just placing insulation between the joist ends or going further and also placing insulation between the fascia board and the joist ends? I might as well get it right as I only want to do it once.
Hi Steve, thanks for clarifying this detail. I'm not a roofer but have asked a few in the past about the between joist unfill that you outlined here and they have never given me a good reason why they haven't put it in, apart from no one ever does! Can I ask how you protect these infills with a vapour barrier? They're obviously under the barrier that is protecting the main insulation layer. It could be that no vcl is needed because the infills have air flow around them...albeit not designed in vents but ventilation through gaps in the soffit? Thanks
I’m wondering? On the warm roof in this example. Don’t you need to introduce any ventilation on the facia at all?
Great video!
Hi Steve
Thank you for sharing your knowledge and thoughts on warm deck insulation. I agree every area must be dealt with otherwise there is a breakdown in the system.
I've watched your vid showing why using thermal mushroom fixings on a warm flat roof is a good idea. My concern is that any penetration through the VCL barrier is a breach and will leak air into the warm deck. The manufacturers say there isn't a way to seal the screws penetrating the VCL, that bitumen backed VCLs do not seal the screw holes.
So for the above reasons I'm building a warm deck flat roof using IKO primer and bitumen backed VCL, adhering the PIR to the VCL, a ply deck on the PIR, with a final 3 ply Technatorch system to finish.
I'm wondering what will happen if I do not fix the final timber deck that will be sandwiched between the PIR and Technatorch felt? given it will be contained on all four sides and not exposed to wind and uplift...
Many thanks
You have to think of wind uplift even if it's contained the top must be fixed down
Thanks Steve, talked this through with a friend and realised I'm trying to marry two different systems because of the materials I was left on site by cowboy builders, the Iko self-adhesive system eliminates the need for the upper deck so going to go with that...have a nice day...
Thanks for taking the time to create these videos. You mention insulating the end of the rafters to avoid the dew point.
Q. How would this be achieved? A run of 10mm kingspan or suchlike down the length between the rafter ends & facia? I guess it would be sensible to just return this round the my 50mm soffit as well?
Cheers Steve
Absolute diamond geezer. Thanks for all your kind free advice. I'm building a garden room 6m x 7m, flat cold roof as I am limited to 2.5m height. Through ventilation through and across the span of the joist is 100% on my mind now. I have to rows of 2 noggins (400L, 225H, 47W) would 2 1.5" holes do on each noggin to allow the air to travel across the 6m span nicely (above the tightly fitted insulation)?
I just watched this video and it's great and well explained but you didn't actually tell us a solution for the cold coming through the fascia of the retrofitted warm roof? Did I miss someone? 🤔😂
wow - great video - great explanation !! Thank you !!
This was exactly the problem I've been looking for an answer to, but you still didn't explain how to actually go about solving it. You say add some insulation between the joists... but what type and how much, where it terminates or interfaces with vapour barrier, etc.
Thank you very much very informative. I do have a question. So there is this company that came and Gave me an estimate for dense packing with cellulose. So they either will shut off all vents.
What I would like to ask them to do is to actually leave a few inches so they are actually leaving the air though I think that there will be some kind of air movement still that could bring me some problems.
Would you do dense packing on a flat roof and if yes how? I still have vents all along the Front and the back.
Good video very helpful 👍🏻
Can you warm board the ceiling
Thanks for the video Steve! What type of insulation would you put in between the joists to insulate the fascia board? Can I use wool type or does it have to be celotex?
Steve you are some kinda bloke mate.
Great video great video Steve. I know this video is 10 years old but can you still have the insulation sitting straight onto the joists without a deck below as per the video
Your always have been told you can do it, but it doesn't work very well. Think about it how do you fix the Air Vapour Control Layer (AVCL) if there is nothing to fix it to?
@@SteveRoofer thank you very much for your reply. I only asked as I am a complete novice. I had my extension done and this is how the builder built the roof. Due to height restriction. The builder put 100mm celotex on rafter with 50below to make it a hybrid roof. He then put a layer of green vapour layer under above the plaster board.
@@Karan-Singh999 is completely wrong if you're going to insulation above and below. The golden rule, if you're not gonna do calculations, is to keep 3/4 of the insulation above. The vapour barrier should then go under the 3/4 that is above and should be continuous and should be airtight. this doesn't mean that you're gonna have problems it just means that it's not right. Keep an eye on the relative humidity in the room or rooms below and just keep that at a low level 50 to 60%, then you should be okay
Fascinating video! I don't even have a flat roof, but still watched right through. I have a bungalow, with a loft conversion, all done to the regs in 2001, when it was converted. Is it possible to retrofit a warm roof on top of the existing rafters? And is this something that people do (or is is a silly question)?
I don't actually quite understand your question but I think I should be saying yes people do retrofit over old roofs
@@SteveRoofer Thanks Steve.
Fantastic information thank you
Hi Steve, great videos! Quick q for you: can you confirm insulation boards can be laid directly on top of roof joists? Is the board robust enough to take persons' weights when accessing the roof (for maintenance and inspections)? In engineering terms, does it have structural strength to take bending stresses due to free spanning over joists?
If you talk to the manufacturers, they will tell you you can but having done it and worked on roofs that are constructed that way but bounce or deflection as it's called is considerable and I believe it to be an incorrect practice. But more to the point you should always be fixing, extremely good air vapour controller for A warm flat roof. Generally speaking all of these are tar-based self adhesive or torch on products. And they cannot be fitted without lower decking so the question should be how are you gonna fit a proper air vapour controller? Now there are some out there which are plastic and are extremely, vapour resistant but installing them correctly over the top of the joists would be a bit of a nightmare not only that how do you fix them to the perimeters?
Great video
Glad you enjoyed it
Yes, you dontwant to put more than 1/3 of the quality of the warm roof under the decking
great explanatory video, thanks for that.
i'm not a builder as such but i am going to erect a garden room with a warm roof. a quick question please. 'what is the best or recommended way of fixing the 100mm insulation and OSB boards down onto the joists below please'?
Use thermally broken fixings, I get ours from fix fast.com
Great video, what if you have boards over your joists and want insulation on top of that, where does the vapour barrier go?
It alway gos just under the insulation . So lay the boards then the AVCL then the insulation
Hi steve, this channel is like a godsend ❤ ive so many questions we got totally played and have a terrible job on a roof of a joining area between old building and our new extention, luckily it is still open inside and has leaking torchon felt on top so maybe theres still hope... ive wondered about making it a warm roof but we are tight for external height would under 4 inches of insulation externally be ok?
Yes, 4 inches is okay however it isn't to the building regulations so you wanna see whether building control will sign it off that's if you need it signed off
Thanks so much for reply. I wonder could i send you a video for advice by any chance?
@@emeraldgreen6150 yes just email it over
great video, well explained. Thank you. How is the insulation (above the joists) fixed down?
Very well explained video with not a drop of ego in sight!!
I’ve recently retired after 50+ years plastering.
On new builds many years ago they made us install a vapour barrier on the ground floor ceilings before boarding and plastering!
Like a lot of things, great in theory but in reality it caused the ceiling to sweat ie condensation occurred!
This was perhaps because the builder wouldn’t go to the expense of foil backed boards!!
Either way it still gets punctured with the fixings so a waste of time as no issues with the houses without a vapour barrier after 40 years!
Shaun 😊
Assume I’ll need 2 mushrooms per section an either end for cross ventilation? I have no other way of getting air in and out as facia boards are place of the brick wall. Thanks
Hi I have a concrete flat roof and would like to convert to a warm roof and use the outer building as a office, any advice on this please. Keep up with the videos, as I haven't done anything like this before and watching your videos and how you explain the what's and where information has given me the confidence to have a go myself thank you.
Shayne Walsh Hallo here in Canada we have a air space between this spaces sow our wood dont get from one side too cold in otjer side warm we used mainly cold roofs we simply add enough insolation. and ventilation between roof and space sow we do not have condensation and it works great for over 100 of years.
You should check if any moisture builds in your joist system this ones are usualy the ones that give you black nails or as we call it the flys on the roof ! hooe it helps.
Good question you wont get a strait answer from any one unless you are paying for calculations.Insulation people say that the foil is part of the insulation however you can you it as a vapour control layer if you want! So read between the lines The best materials to use as a vapour control layer is a thin layer of metal its better than felt 2 layers of felt however you must seal all joints even the screw holes, felt tends to auto seal around screw holes.
Hi Steve Roofer, how can I Achieve warm roof stronger to be able to use it as a decking for the first floor as I am opening a door into flat roof?
Thank you
Han
Thank you for these videos. This is a very important area to consider for sure. Back in the day when these roofs and walls were constructed, they clearly had no concept of thermal bridging and left plenty of uninsulated areas, effectively negating the effort of the installed insulation. One thing I have noticed with your videos is that you tend to use one think layer of polyisocyanurate rather than 2 orthogonally placed layers. I assume this is done to reduce labour costs and benefit from the slightly nonlinear R values inherent in polyiso. However, as I understand it, ASTMC1289 allows for up 4% movement in polyiso boards which can leave large gaps at the joints in cold temperatures if the boards are installed in warm temperatures. Plus, each board may respond differently, so even if installed in cold temperatures, gaps may still open. These gaps are then thermal bridges similar to your video (smaller albeit). I noticed also that you use a protection board over the polyiso to provide a separation between the membrane and the insulation. This layer does reduced stresses in the fully adhered membrane as a result of insulation movement.In Canada, we have large temperature swings and expect significant movement; as a consequence, we typically use a double layer of orthogonally placed staggered joints for flat roof insulation.
Verrry interesting and thanks for your comments. In the UK nobody is really taking any of this seriously, nearly everything is based on cost, not performance. The detailing I try and achieve nearly prices me out of the market. Your point about expansion and contraction of the insulation is a new one on me, I've never heard of this or seen it over here, however, I can quite believe its a problem, yes a double layer could help, edges that are jointed and not just butted could also help but again more costs.
I can see that. The temperature swings are relatively small. But as you mentioned in your video, comfort can be a driving factor. If occupant comfort is as important as the water seal, then there is no point taking the lowest bid if the resulting job only provides a moisture barrier but leaves the occupant shivering. Why bother with the insulation at all if there is a big hole left. Hopefully, your potential clients are able to evaluate long-term benefits and value over short-term considerations.
Details here were not always performance based either. But now, we have a new energy code which has just recently gone into effect. This is going to change building design substantially or will drive innovation in materials and systems such as windows. Performance is the driving factor and I have heard it said that it will be very difficult to meet the code in many cases. Also, some say that the next 5 years will see many science experiments as uninformed contractors do things like trap moisture in an attempt to increase thermal performance. It's cool that you explore options using models. I find that a good way to visualize also. Keep up the good work.
Building regulations are also getting tighter and tighter here, we have nobody policing things. Roofers and builders get a job with a specification. Knock the job out and move on. Local authorities assume the job was completed to the correct regulation as that's what was supposed to happen but under the hood everything is different. Thant worked for the builder or roofer before but now we are finding they are getting caught out when condensation and thermal bridging happens. Unfortunately, this problem only raises its head months later and then the builder roofer has gone. This is a particular problem with London as we have lots of work going on, transient tradesmen at cheap prices here one day, gone the next.
I think you are on the right track. Keep learning and delivering a quality product. Your satisfied clients will be your best marketers. Yours is a long-term (and repeat) business.
Whats your conetion with this subject?
Brilliant video, quick question,I have started my extension and it’s with a warm roof, but are there any negatives to also insulating in between the timbers fully? Just trying to keep all the heat I can!? Thanks x
Shouldn’t the title say warm roof rather than insulated roof?
The video is long because you go off piste and don’t focus on the main point in the title, which you didn’t spend very long on.
Thank you for highlighting this issue though.
That's a big help mate. Thanks.
Hi ,
I'm doing a warm roof , your vids are very good.
Just one question, I'm using 300mm fascia boards so where the 120mm insulation is there's going to be no solid fixing s .
Would would be the answer?
Many thanks
Stuart
nice video stevo . couldnt find the link for the behind facia detail. fitzy
could you use structural insulated panels and if so do you have any advice. Flat roof on garage that we are making into a wash room. Thank you.
I don't see why not its something I would try have never seen SIPS panels used on small domestic roofs but its basically what they use on large jobs. Keep me posted on specifications as sounds interesting
Hi steve
I love your videos and I’m doing a 4 meter extension on my house with a warm roof with a Epdm finish
What are the layers now as you said in a comment that you put 18mm osb first then alutrix 600
Then 100mm insulation (should it be foil backed or not ??) then rubber straight on top or another osb board please could you do another video to update us please
Hi Steve
Thanks for your great videos, a question on the warm roof, you mention in detail about the cold bridging at the facia, that this will cause the due point to condense the warm moist air that’s come through the plaster board, I get it, insulating the facia board, I get it, the question is where is the moisture going ? You say no ventilation required. Would it be wise to fit a moisture barrier above the plaster board?
Many Thanks
Steve Crockett
Believe it or not there is no joint up thinking the only thinking is don't let it go into the roof. The problem being we tent to do a retrofit on a bit by bit process. IE upgrade the windows one year the heating other the walls another and the roof another If we only had a plan and stepped back and thought! (What's going to happen to the moisture?) Basically, it goes to the next weekend point int he property when we dont plan things correctly. When we plan things correctly we use MVHR (Mechanical Ventilation with Heat Recovery)
hi just wondered if you could help to put some light on to the part where you talk about the warm roof and the space between the joist's and putting insulation in there... do you put it on top of the outside wall up tight to the fascia? and what type of insulation?
would just like to say thank you for doing your video's, any advice would be great thank's
Hi, yes same question. Would you fill this gap with insulation tight to the bottom of the roof deck? And would it be best to sandwich this between wooden noggins?
I had the same issue and my builder has just done as you said and installed insulation in the joists, but my question is what about the sides how do you insulated them
Very good video I am a student at university studying a degree in construction. I was wondering if you could advise me on the best books to buy on cold and warm flat roofs? And do you have any detailed diagrams on them? Thanks.
Very well put togethr video Steve, and really useful for us to see the difference between cold and warm roof construction. Would you recommend warm roof construction for garage conversion and would it use the same technique? I planning to strip our old garage down to simply 4 walls, with pitched gable ends. Run trusses along the wall plates, insulation on top of the trusses, OSB, membrane, then finally tin roof. Would it be okay to cut and fit pieces of insulation between the eaves, or better to fit long strips of insulation along the truss ends covered with fascia board, followed by the membrane over coming down into a gutter, like in your plan? Appreciate your advice, keep up the great work!
Hi Steve. Great vids mate. Learning a lot from them. Regarding the insulation between the roof joists to insulate the facia, (warm roof construction) what do you do about the VCL? As this is on the sub deck. Do you need to try and get VCL sealing in-between each joist?
Technically yes otherwise the vapour gets through at joist/ insulation junctions and condenses in the fascia and soffit area. If you vent the eave area without a VCL then cold air just circulates under the warm roof. The insulation at the eaves should be continuous with the warm roof insulation. How good your detailing around the joists to ensure a continuous VCL is where the difference is made. Gapotape is definitely a good aid in a solution to this problem.
The AVCL to the roof is one thing the AVCL to the wall IE between the joists has to be the same as the rest of the wall. Wall AVCL is different to roof AVCL its a much lower standard So as long as its air tight you will be ok
Do you need to add Vapor barrier to that part too ?
Great info explained very well !!!
Would you not lay the insulation on a deck rather than straight on the joists to spread the load ?
Yes, we already do even though supposedly you don't have if you talk to the insulation suppliers. The video above is about the front fashia and not about the warm roof all of my other videos clearly show the lower decking going down. It necessary so yo can lay a good AVCL (air vapour control layer) onto it and make sure its comply sealed
great video, thanks
By putting insulation between joist to insulate the soffit, does the cold bridging from the timbers matter?
you dont even have to overlay with the 9mm you can glue EPDM direct to the insulation or you can buy insulation with 6mm ply bonded to the top however think abut how you are going to fix this try to glue or use a fixing thats thermally broken
Hi Steve, Great videos and great use of modelling software.
I’m looking at having my conservatory roof replaced with a warm flat
roof and am really interested not mention concerned at what you have correctly
pointed out with regarding cold bridging through the facia. How would you recommend to best overcome please?
My thoughts are to use kingspan panels between the joists from the overhang (back
of facial) to the inside face of the conservatory in my case. Ideally though Finally would this problem also occur around roof lights? Sorry for all the question, but your help and experience would be really appreciated. Many Thanks & Kind Regards, Andy.
I guess this would then need some kind of vapour barrier placing across the back of the insulation too? Also would you allow this small section of
insulation between the joists to fill the full depth of the joist or leave a
gap as you would on a cold roof system?
Great video, thanks for the advice. I do have one question though, I have built a flat warm roof and about to insulate inside where the overhang and fascia boards are (between the joists). How do you go about adding in a secondary vapour barrier or do you not need one?
The vapour resistance of the wall is different than the roof and realistically you should match the surrounding walls vapor resistance, but as its not a perfect world you probably don't have a VCL in the wall so don't worry . JUst make sure its fully sealed and air tight
I’m in that situation right now. What insulation did you use?
@@SteveRoofer would you use cavity wall insulation for this? Or PIR to match the roof? Great videos!
What to do with concrete flat roof about 6 square metres? Do I need install timber frame for 145 mm insulation boards or just stick boards with flashband and cover with cap sheet felt?
On the warm roof do i need to put down a decking under the insulation boards too or is can go straight on top of the joists and use the decking on top of it?
Always put a lower decking down it's Gotta be the only way to go how can you add a vapour barrier over joists before your installation there is nothing to support it
@@SteveRooferso double decking the right way to go?
Hi thanks for this video, very helpful. I'm just doing a warm room. Where the joist meet the house should I bolt a timber across and use hangers or send them into the brick work and point them up?
Many thanks.
use hangers
Hello Steven, I'm in the US. I have a dormer that I'm re-roofing (cold roof) and am looking for advice on the best way to insulate. I'd like to take off the sheathing and put in cellulose . Would you recommend this?
Not necessarily but I think we've had further discussions by email and I think I've sorted it out if not get back to me
If you really want to do the best job, with regards to a timber frame, like a dormer for example. Have both ends of the roof joists on hangers. Don't sit it on the wall plate. You can insulate alot better as you don't have a top plate to sit on.
where do you put the vents to allow 'through' ventilation ? surely you've only got two choices; 1 down through the ceiling and 2 through the joists,to allow air flow. ? should you vent between each rafter?
What’s the best roof to put on top of a flat concrete roof?
EPDM
Hi Steve, do you know what the thermal efficiency difference between a cold and warm flat roof is? In percentage terms perhaps.
Lets say with 2" x 8" rafters with 100mm celotex, 18mm ply and a felt cover cold roof compared to same rafters, 18mm ply deck, 100mm celotex 18mm ply EPDM type top layer.
I hope that makes sense. Thank you.
Does adding insulated plasterboard affect the flat roof in any way,including the ceiling joists ends??
Yes, it does because it upgrades the thermal property also stops them pushing through the joists so definitely a good thing to do
For a warm roof. If that overhang had soffit lights in it, like infront of bifold doors, could you still fill with insulation. Electrical safety problems?
Yes you can because it's a separate area if you've sealed the wall above the bifold doors you've got an internal space and an external space the external space be in the area between the joists i.e. the canopy area. This is a free area. You don't have to have movement of air but you can if you want to and you can put lights in if you want to
Great video, i am doing a flat roof right now, and its over a single storey extension, i am planning to do a warm deck, however I plan to put balustrades over it to use the area as a balcony. How do I go about the problem,?
Adding railing to a warm flat roof is not easy as I'm sure you have worked out. Warm flat roofs are basically floating so there is nothing to fix too. We assess each job separately and work out how best to do it on a job by job process. Perhaps you want to send me drawings over and I'll give my opinion.
Hi Steve.
I see you point about the heat loss from a warm roof. If you added ventilation between the joist to protect against a dew point and heat loss would you need to ventilate as well?
The facia insulation. On a warm roof....if its a cavity wall ...do you put the insulation ln front of the cavity or tight up against the inside of the facia after the cavity ....your illustration shows a solid wall ...please advise thanks
It only needs to go above the inside caverty wall but no harm in filling right across if you want