Stop Roof Damage: Insulation Secrets Revealed!

Steven Dickinson
London Flat Roofing
07802300099
[e-mail]
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.londonflatroofing.co.uk/wa...
Steven Dickinson
London Flat Roofing
07802300099
[e-mail]
@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

[@markhathaway6673]

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 👍

[@ChicharonyPresidente]

Excellent video. Great detail and explanation. You should be a construction teacher. Learned a great deal from watching this. Thank you.

[@kennethgillingham2093]

Exactly the information I need on Warm Roof fascia insulation. Many thanks.

[@THEGizzardPuke]

All of your videos are most informative and well presented. Great work! :-)

[@drawingboard82]

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 :-)

[@rickywanless2239]

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

[@gingercat555]

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 ;-)))

[@SBIGDTSM]

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.

[@paulthornton9899]

😅

[@inthewildwoods]

Fantastic. Thank You very much. Well illustrated and expertly explained. I have viewed lots on KZbin and this is the best on this topic. I am building my man cave this spring and thanks to you have decided to do a warm roof. Thank You so much.

[@guseireann]

Smashing video. Thank you very much. Just what I was looking for

[@tonyjoyce8576]

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.

[@SteveRoofer]

Thanks the information i'm getting is moving all the time we are now being told not to use any timber above the VCL?

[@wsherratt5159]

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!

[@SteveRoofer]

Glad it was helpful!

[@alisonsalt5149]

Very well explained with good 3d illustration.

[@rosebonner524]

Architect here! Great informative video. Thank you.

[@buddybeetle]

Excellent detail and info. Many thanks Steve !

[@AfricanSouthernCross]

Excellent video….thank you for posting this…BRILLIANT !

[@CH-gb7hf]

Quality video. Very helpful.

[@dumptonpark]

Excellent, Thanks for sharing.

[@donho526]

Great job. Very informative.

[@mbotes6691]

Very nicely explained , well done !!

[@DorkyThorpy]

Well done, another great video. Thanks.

[@MrJohnnynapalm7]

Very good explanation - thanks for sharing.

[@MrMagsimus]

What a fantastic informative video !!👍

[@chaswarren7239]

Thanks Steve, great concise explanation.

[@SteveRoofer]

Ok thanks

[@bennorthover]

wow - great video - great explanation !! Thank you !!

[@margosdesarian]

Great video!

[@MyJerome26]

That's a big help mate. Thanks.

[@joshuaemmerson7878]

Fantastic information thank you

[@popandu8297]

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.

[@MrClowny666]

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.

[@vindicator2008]

great video, thanks

[@The727Kidd]

Great video! Thanks.

[@harvey19750]

Excellent thank you

[@roymichaeldeanable]

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

[@SteveRoofer]

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 !

[@MylesGascoyne]

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.

[@omegadevelopments]

Good video. Thank you

[@sten40too1]

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?

[@end-game2030]

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)?

[@fireboyspirit3474]

Good video very helpful 👍🏻

[@andyf3707]

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?

[@emilymerrifield]

Hi Steve, thanks for the informative videos. I hope to have a new flat roof on a fill in extension and wanted to know if it was possible to install roof windows and still have a "warm" roof and if it was possible to install the insulation effectively around the kerb for the roof window? Also does your company work in Brighton? Thanks, Mark

[@wildbill100]

well explained. thanks

[@AllenHart999]

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.

[@SteveRoofer]

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

[@voodoomotion5855]

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!

[@tinrobot1746]

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.

[@SteveRoofer]

Sounds interesting. Send over some photos

[@tinrobot1746]

@@SteveRoofer Many thanks - sent to info@

[@SteveRoofer]

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

[@SteveRoofer]

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.

[@link_7164]

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?

[@j0hnkreelman]

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

[@ice8846]

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?

[@joegrimley9327]

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

[@ManiSingh-jc2ff]

Great video

[@SteveRoofer]

Glad you enjoyed it

[@jeromeclatot1769]

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.

[@Prawnchowmein]

Great vid u know your stuff son

[@scottmcarthur4022]

Steve, if constructing a new garden room with a cold roof construction(due to height restrictions via permitted development) how do you get around the noggings at midspan (4m span of roof). These will prevent air flow from back to front if they are full depth. Ideally they need to be at the top of the joist to prevent twist in the compressive zone of the joist. Would you suggest attaching them 50mm below the top of the joist or will this not be suitable to prevent twist in the joist? If the osb above is nailed/glued, would this be suitable to prevent the twist? Thanks

[@zororat]

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!

[@SteveRoofer]

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

[@oc1625]

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

[@jonkers9505]

Hi Steve I have watched several of ur vids, great thank you. My problem; I have a top floor flat with a flat roof circa 1969 hot roof design with woodwool slabs on top of the joists with no venting. would it be okay to upgrade insulation by blowing thro holes between the joists in the ceiling fire retardent polystyrene beads? If not what do you suggest?

[@JasGawera]

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😢 🤦

[@SteveRoofer]

that's not a bad specification, but you can't cut through the space blanket

[@christopherwillmott4783]

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

[@garethmillers5453]

Thank you Steven, this was a very helpful video.

[@SteveRoofer]

No problems glad it helped

[@peteramberley9952]

nice video stevo . couldnt find the link for the behind facia detail. fitzy

[@joshuamathew2689]

Hi Steve, I have been told I need to have a warm roof on my 12 m long rear extension? I am planning to put the Alutrix on the osb then 120 mm insulation and another osb before GRPing. Would you suggest that I put insulation along the three sides behind the fascia board under the first osb like a cold roof? Does that not defeat the purpose of a warm roof?

[@tellylgeorge]

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.

[@chris-ryan]

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.

[@stuartbreeze6398]

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

[@paulkormany7406]

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.

[@SteveRoofer]

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.

[@kingcobrauk]

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

[@LifeStyleMemories]

hi steve what is this vapour barrier called? in this warm roof

[@jeffrey01UK]

I have a cold roof ( 1970s dormer extension ) I am considering installing high u value ' thin' foil insulation under the very limited expanded poly insulation. Doing this by cutting a 10 in slot in the plaister board celling at the edge away from the vents and slide the foil in. Would this be reasonable solution ?

[@jeremylister89]

HI Steve, I've a bungalow with two bay windows, both with not very thick flat roofs, each stand away from the main house by about a metre and they are about 2.5 metres wide. I suspect there is just some short joists, then on the top, maybe plywood and then felt, on the bottom some thin plywood ( or even hardboard!), plaster skim and gloss paint. In winter I get condensation on this and dripping onto the window sill. As the flat roof is flush with the end of the main house roof I have no height available to fit a warm roof. Apart from the dripping, I suspect I am losing a lot of heat. Whilst I can live with this, it really needs sorting out. What solution would you use? I have not managed to find anyone who can sort this out for me.yet

[@dougalmacpherson9610]

Top man thanks

[@jackclements7410]

Hi Steve. I know this video is now 9 years old but is this still current? I am mid build on an extension and this was my concern. I was planning on putting a noggin in at the inside wall and insulation’s the outside area as you mentioned, but I am having downlights fitted within my soffit boards. Is this method still practical with 8 inch timber and 100mm insulation? or would there be a better alternative? Many thanks

[@BigJProductions]

great video, well explained. Thank you. How is the insulation (above the joists) fixed down?

[@shaunmurray7398]

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 😊

[@markaitken4930]

How do you ventilate a cold flat roof if you can only get to one side of the roof? I'm about to insulate my garage roof (putting in an office) but my garage is attached to a neighbours and I can't therefore cross vent? Any ideas appreciated. Mark.

[@CKDJBOY123]

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

[@jamesbrown8908]

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?

[@JamesMasterPlaster]

I must send you all my pictures of my failing flat roof 🏋️‍♀️🤺👍🤗

[@theslovakiankid5959]

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?

[@nssimpson]

Would you recommend anyone in Stockport that can do a warm roof on an existing watertight attached single garage. Any idea how much the materials cost and how much I should pay for labour?

[@makolic1]

Hi I did a warm roof but I put up vented soffit . I guess it should not have been vented . Would it cause any problems ? Thanks

[@klaeLIFE]

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

[@SteveRoofer]

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

[@lukehedges2976]

Whats the best option for a re foof? Strip off old felt and deck or insulation over old deck and re felt?

[@marnsmusiccovers147]

Hi Steve...what is the red thing represents?

[@FBL297]

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

[@leighlin007]

In terms of the insulation that should be used out to the fascia, on the inside of the roof, is this a rockwool type insulation that fills out the gap from the outside wall to the fascia? Or do you put a rigid piece of insulation e.g. Kingspan/Celotex that fills the space between the top of the inside wall to the underside of the decking board on top of the rafters, which in turn will stop any warm air reaching the 'cold' fascia board?

[@SteveRoofer]

Solid Kingspan or anything equal to the thermal performance of the weakest point of the construction at that point

[@stevencrockett7280]

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

[@SteveRoofer]

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)

[@Jamieh321]

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.

[@jamjys]

Hi, is the foil on the underside of thermal ply deck 120mm , the VCL vapour control layer or do you have to install TORCH ON FELT Aluminium Vapour Control Layer any help much appreciated,

[@MichaelJordan-hn4zd]

Thanks for the video! I didn't know about ventilation. What size foam do you use for a warm roof? Is it just regular foam or a SIP? I looked at SIPs and they are like $200 each. With a warm roof, do you just use long screws to attach the plywood through the foam into the joists? Thank you so much

[@SteveRoofer]

the thicker the better on a warm roof. Typically in the UK new warm roofs on new builds have 150mm retrofit properties have 120mm Its SIP insulation

[@MichaelJordan-hn4zd]

What R value do you use on top your roof?

[@meganwood9591]

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.

[@HampsteadBuildersLt]

use hangers

[@anthonydevincentis5932]

Great video! How do you properly vent a cold flat roof at the back where it meets the wall? I know someone with a bad moisture problem with there bathroom addition. I did not see any fascia or soffit vents so I would start there but what is needed to vent the back of the roof and not leak? The bathroom does not have a vent and I saw the plywood sheeting for the roof during a ceiling repair and it was just wet. I had to replace some of the joists. She needs a new roof obviously. Thanks for your information about warm and cold roofs.

[@SteveRoofer]

Any way you can taking into account that need ventilation to cross the roof from front to back or side to side. the vents need to keep water out and to stop pests from geting in.

[@lukegannon84]

Great video. How did you manage to get Glen Hoddle to do the voice over?😁 I'm doing a warm flat roof now. 6m long with firring pieces. I'm now trying to think my way around the back fascia being 400mm high. Any suggestions welcome

[@SteveRoofer]

I did his roof

[@alane3983]

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.

[@SteveRoofer]

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.

[@alane3983]

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.

[@SteveRoofer]

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.

[@alane3983]

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.

[@SteveRoofer]

Whats your conetion with this subject?

[@myatix1]

Hi Steven, How would you do through ventilation for the cold roof? In your drawing you don’t show where the ventilation would come out on the joists against the building? I have a problem with height restrictions for our roof so I can’t do a warm roof.

[@rogerbean393]

I was thinking the same how you get airflow from the building the new roof is attached to.

[@Chemikill10]

By putting insulation between joist to insulate the soffit, does the cold bridging from the timbers matter?

[@andykimpton7877]

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'?

[@SteveRoofer]

Use thermally broken fixings, I get ours from fix fast.com

[@marcozeta2581]

this video is amazing Steve very useful ..... thank you for posting it online....very recently we have started a loft conversion we tried to carry out the work by ourself with the help of a friend. our architect not bother to answer our question we have paid him £2000 two time we called him for information he is keep saying look at the paper work... but his paper work doesn't make any sense. its is flat-roof anyway if you can answer my question I would be very thankfull 1. after the timber joists do i need to put chipping board if yes what type and size? 2.is the insulation comes next and according to my plane is 125mm tick kigspan Tp10 do you recommend anything else? 3.what goes next, at this stage do we have to put breather membrane ? or just another layer of plywood or chipping board. 4. then final stage Fibreglass. if i have missed anything else can you please let me know ..... thank you Steve

[@SteveRoofer]

if you still need help email me [e-mail]

[@shaynewalsh1950]

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.

[@allconstruction1]

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.

[@gabeanthony8910]

Great video! Question, what happens if you don't have ventilation in the cold roof? If you have insulation in between the joists and below it, would any hot air realistically get up there?

[@SteveRoofer]

If everything is tight very little will get up there but if the RH relative humidity in the room below is high and it does get up there then there could be problems so best to vent, the venting is your second get out of jail free card

[@davesunts08]

do you know of any vents available for flat roofs with a facia but no soffit?