Dormer roof insulation (warm deck)

Рет қаралды 36,990

3 жыл бұрын

This video shows the correct way to install a warm deck roof in a loft dormer - it's a fast and highly effective method for insulating the space, while allowing a ton of room inside the house to run cables and anything else you want to within the rafters.
All the insulation sits on top of the dormer roof, rather than inside the rafters, achieving a better U-Value for insulation, and it gets installed quicker (and with less mess!).
Here is the kit I use:
Bosch Professional Combi Drill and Impact Driver with Two 18V 4.0 Ah Batteries amzn.to/2owE0mK
Bosch Professional 18V Cordless Circular Saw with 2 x 18 V 5.0 Ah Batteries
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Bosch Professional 18V Cordless Multi-Cutter with 2 x 18 V 5 Ah Batteries and 16 Accessories
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Bosch Professional 18V Cordless Jigsaw with 2 x 18 V 5.0 Ah Batteries
amzn.to/2IDgTxA
Bosch Professional GAS 35 M AFC Wet/Dry Extractor
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Bosch Professional GMF 1600 CE Corded 240V Multi-Function Router
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Occidental Leather 5089 LG Seven Bag Framer Tool Belt
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Occidental Leather 5355 Stronghold Comfort Package
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Hikoki Nail Gun
rover.ebay.com/rover/1/710-53...
Bosch Table Saw & leg stand
rover.ebay.com/rover/1/710-53...
Damp Proof Membrane
rover.ebay.com/rover/1/710-53...
18mm Chipboard Flooring
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Пікірлер: 70

@mikew151Manhattan 2 жыл бұрын

i never knew bear grills did roof tutorials!, great vid - perfectly explained

@davey4697 3 жыл бұрын

Vapour Barrier is missing, and is a crucial element in a warm-deck flat roof. Thermally broken fixings are missing.

@celticstoneworks.construct4570 3 жыл бұрын

this is what i noticed first off.

@Brandon-no3vc 2 жыл бұрын

That's what I'm sayin

@Brandon-no3vc 2 жыл бұрын

That's what I'm sayin

@edmarferreirajunior724 2 жыл бұрын

The aluminum foil covering the rigid insulation board is a vapour barrier.

@real_wakawaka 2 жыл бұрын

@@edmarferreirajunior724 LOOOOOOL no its is 10000% not! this will not pass building control. Also the screws should be in a plastic sleeve to stop bridging. Nice looking but in 1 year the roof will be rotten!!!

@MrFlatroofer 3 жыл бұрын

Did a building inspector pass that roof? Because he should not have.

@kithdhasengh2013 Жыл бұрын

Thanks for uploading the vid. KZfaq is proving to be great community for learning and peer review/constructive feedback. I'm thinking of doing a warm roof too for my garden room. Pitched roof though. The roof covering will be asphalt shingles instead of rubber EDPM. Vapour barrier and ventilation aside. Any views on using shingle instead of rubber would be welcome. Thx.

@carlreed1000 3 жыл бұрын

I think that needs a vapour barrier under the pir otherwise in

@harrysingh1145 3 жыл бұрын

Agree u havent put a vapour barrier in u need this warm deck roof. Also the screws u need a special fixing which the screw goes into because of thermal bridging.

@mrboyban 4 ай бұрын

@@harrysingh1145 Zinc screws have a very negligible thermal conductivity, besides will allow you to run the EPDM smoothly with no bumps left by the SureFast tube washer.

@albopastrami9269 Жыл бұрын

hmm, you need to put a vapour barrier underneath the kingspan

@paulsmith3652 3 жыл бұрын

Excellent video, perfectly showing a builder not fully understanding the principles of a warm roof construction, missing the Critical vapour barrier, 25mm expansion joints, as others have pointed out. Hopefully the building control will pick up, before the is finished.🧐

@arbit3r 3 жыл бұрын

25mm expansion???

@johnvinnicombe8406 3 жыл бұрын

No vapour barrier or leaving a 3mm gap between boards?

@chrischarlton709 3 жыл бұрын

Really enjoying your videos, really clear and well explained - looking forward to working my way through the rest over lockdown! I would however would also like to flag the need for a vapour control layer beneath the insulation as others have done. It is recognised best practice and is recommended by all membrane manufacturers and building regs, so the fact the roofer doesn't agree is basically irrelevant. I'm certainly no expert, but regarding the OSB over the insulation comments flagged already: I imagine it might make a difference how much moisture is trapped at the time of the install; if it had been raining and water was trapped in and around the insulation then I can see that being an issue over time if the moisture can't escape. If the build-up was quite dry at the time then its perhaps less of an issue? My understanding is also that a certain amount of water vapour will escape over time as the roof heats up in the sun so I would probably not be too concerned. That said i would rather have the VCL than the OSB - if the OSB is there for convenience of install then it is surely only a marginal benefit in the grand scheme of things? if its there for robustness - who is ever going to walk on the dormer?

@OfficeBoyBuilder 3 жыл бұрын

Thanks for the support mate. I agree with everything you've said mate, all your observations are spot on. Thankfully it was very dry and stable when we installed, and the insulation was nice and dry too, but yes, a vapour barrier would have been best. I know that the foil facing of insulation acts as a vapour barrier, but the membrane is different and necessary. On my more recent builds I've done that.

@Brandon-no3vc 2 жыл бұрын

For one you didn't space your plywood for expansion and contraction for 2 you didn't use vapour barrior for 3 you didn't use thermal braking fixings for 4 shouldn't the thicker plywood be on the bottom?

@keithsutton8145 2 жыл бұрын

Where is the vapour control layer

@johncoppock3823 2 жыл бұрын

Warm roof way to go if you have the headroom to play with. Important to get all those details right to avoid making a rot box.

@Oncewasdonka 3 жыл бұрын

Thanks for taking the time to show us this. Could I ask as a client why would I want to lower the internal by having a warm roof? If you understand. Thanks

@OfficeBoyBuilder 3 жыл бұрын

In terms of loss of head height, it's actually negligible (40-80mm) because on a "cold roof" where the insulation is between the rafters, you need them to be deeper in order to get the same U-value. Because of this you end up spending more time working on them (notching to install and cutting insulation to fit between) and you also have less space as a service void to run your cables and lights. I think that the small loss of head height is definitely offset by speed and ease and the definite increase in insulation levels.

@Oncewasdonka 3 жыл бұрын

@@OfficeBoyBuilder cheers you explain things very well. Loving this one.

@Craigo5000 3 жыл бұрын

I'm still insulating my cold deck dormer conversion (6.5x5.5m) and my main worry is condensation. I've continuous soffit ventilation across the front face and both cheeks, a 50mm air gap above the 100mm insulation, foam filled any tiny gap due to rafters twisted or a mm or two out, then made sure all wiring was tacked above the 100mm insulation which I then cut a square hole in, fitted Thermahood for 20 spot lights, back filled those with more foam and capped them with a 30mm PIR layer AND THEN under drawn all of that with a 30mm PIR layer and taped all the seams. Building regs also requires a further vapour control barrier so yes, cold decks are an absolute hassle because if you have any breach in your PIR for spots etc, you will have ineffective insulation, risk condensation build up in the structural timber. I'm not a builder, I just learnt all this in a few weeks and redid the whole job I paid professionals to do. It's crazy how many joiners and roofers don't understand their own trade. If I'd have known before undertaking the conversion, I'd have gone for a warm roof too. Cold deck roofs are apparently banned by building control in Scotland? I can understand why. They need to be installed properly and sadly, a lot of traders don't achieve this.

@OfficeBoyBuilder 3 жыл бұрын

Mate you've literally written chapter and verse what I've done on my loft...! It's a whole ordeal, Vs the simplicity and speed of a warm deck! Ps. Great work going to all that effort. 99% of tradies wouldn't, and 99% of home DIYers wouldn't know to.

@dannymurphy1779 3 жыл бұрын

@@OfficeBoyBuilder I think a lot of home DIYers do know what to do thanks to channels like steve roofer and others.

@MrGlenfraser 3 жыл бұрын

Have you side nailed them furrings into the roof joists? instead of down through them? Is that more for strength? Thanks G

@OfficeBoyBuilder 3 жыл бұрын

Occasionally the nails hit a knot in the timbers and get skewed off! It's not deliberately shot at an angle in this instance 🤣

@dannymurphy1779 3 жыл бұрын

Whether you can do a warm roof is often down to planning and the slope of the original roof, the dormer has to be subservient to the ridge so you need a big roof with a high pitch. Everyone would build warm roofs if they could but on a flat roof extension there is the issue of the roof looking too bulky.

@OfficeBoyBuilder 3 жыл бұрын

That's a good point. I think there's also an element of not necessarily knowing or understanding the differences between them. If people knew the difference properly, I suspect they would opt for a warm roof in every situation that it's possible to do them.

@liamteal316 3 жыл бұрын

No VCl. 1,2,3 condensation. Then OSB will turn out all mushy.

@b21playa 3 жыл бұрын

Didn’t you need to tape the joins or put in a vapour barrier?

@OfficeBoyBuilder 3 жыл бұрын

Yes you're right, I pointed that out to the main contractor that I was subbing for, and he said they never built them like that and it wasn't needed 🙄

@darrenharlow3016 3 жыл бұрын

@@OfficeBoyBuilder what did it say on your plans or what his the building regs

@OfficeBoyBuilder 3 жыл бұрын

Building regs vs. what gets signed off are two different things sometimes (sadly!). I didn't see the specifications as I was a subcontracting carpenter.

@garychue7343 3 жыл бұрын

@@OfficeBoyBuilder Totally wrong.

@kirkjerram1903 2 жыл бұрын

Ohh dear that’s a fail 😫 Vapour barrier missing

@Jackzuk Жыл бұрын

No Vapour barrier would keep me up at night, 2 years on, how we holding up fella?

@OfficeBoyBuilder Жыл бұрын

As far as I know, there haven't been any issues! The building company I was working for at the time offer a 10 year guarantee on their roofs, so if anything did crop up, it would get fixed.

@dannymurphy1779 3 жыл бұрын

A good example of what Gary Chue was saying below about the osb on top of insulation - kzfaq.info/get/bejne/bLSHpbx4l62WeKM.html You can see that without a vapour barrier the osb will die if it is not vented.

@guatf1 11 ай бұрын

So is the osb on top needed? Or can you also choose to use the rubber roofing directly on top of the insulation?

@OfficeBoyBuilder 11 ай бұрын

OSB on top is absolutely needed. Ideally you'd have thermally broken screws to fix it down. But for the structural strength it is most definitely required.

@DB-bx7hv 2 жыл бұрын

whats the exact spec on that kingspan @ 120mm thk please mate 👍

@OfficeBoyBuilder 2 жыл бұрын

Not sure I fully understand the question...? It's 1200mm thick, and comes in various sheet sizes, but we bought 8x4 foot sheets. In terms of U-values etc. You'd need to check the website because they're quite specific about the conditions needed in order to meet those specs.

@DB-bx7hv 2 жыл бұрын

@@OfficeBoyBuilder bloody ell 1200mm thick eh, BC must be murder where you are🤣! no worries mate and I can see its 120mm thk quinn therm your using

@MrFlatroofer 3 жыл бұрын

That is not a warm roof then.

@albopastrami9269 Жыл бұрын

mate, kzfaq.info/get/bejne/n5phorppmuC0nWw.html

@keithsutton8145 3 жыл бұрын

Check for condensation in building regulations BS standards this work does not comply in an way

@garychue7343 3 жыл бұрын

You should not overlay a "warm roof" with plywood/osb as you are actually turning it back into a cold roof with no ventilation. Correct warm roof construction build up is 1) structural deck 2) vapour control layer 3) thermal insulation 4) waterproofing - True osb/plywood is a nice base to lay flat roofing on but that build up is not correct for a warm roof.

@OfficeBoyBuilder 3 жыл бұрын

There are many different ways to do things, so it's not totally wrong...why would you need to ventilate a warm roof? According to the NBS a warm roof doesn't need ventilating...

@garychue7343 3 жыл бұрын

@@OfficeBoyBuilder Because you have not actually constructed a warm roof. The correct build up for a warm flat roof is as I have stated. I have done 1000s of m2 over the last 36 years and I am qualified in flat roofing and a former Fellow of the Institute of Roofing. Check any major flat roof manufacturers website and they show construction details to back this up.

@dannymurphy1779 3 жыл бұрын

@@garychue7343 that does make a lot of sense, doesn't seem any benefit putting wood into a space where it can rot. 'If it can't dry it will die!'

@jp6975 3 жыл бұрын

@Gary Chue... I'm planning a warm roof project in my garden and all the info I have seen on the planning portals and building regs seem to say nearly the same as you... 18mm osb3 over joists, a good vapour barrier, insulation... and then another layer of 18mm osb3 before putting on the final waterproof layer. Whats the reason/benefit of leaving out the top layer of 18mm osb3 per your suggestion? Also.... one question.... there are gaps between the joists on top of which the warm roof is built-up. What happens with these gaps? Are they blocked and insulated or are they left for air to circulate up and out through the fascia and soffit?

@tonyatkinson8962 3 жыл бұрын

@@jp6975 You can put another OSB layer on top. Some membranes eg fibreglass would need this in place. You can't fibreglass straight onto PIR! Ideally, use thermally broken fixings ie tube washers, along with a vapour barrier and you'll have a good system. Regards to the space in between the joist, do not ventilate- you don't want cold air between the insulation and your living space! But remember to insulate behind the fascia detail (between the rafters) as you'll have a big cold spot there otherwise!