Thanks

This is so interesting, I've had the same problem on my flat warm torchdown roof... Every now and then around 10:00 a.m. and 7:00 p.m. (I guess when the building heats and cools) there is a bumping sound (like something like a pine cone fell on the roof).

If it's a warm roof then any plasterboard will works. All the Vapour control and thermal properties are above the decking.

I really need to understand this correctly before I give you advise, can you email me over some photos of the roof please Steve@londonflatroofing.co.uk

Steve Roofer Will do. Thanks.

Yes however two problems with this method. How do you fix a proper vapour barrier? you can not Go back in 5 years and see how it all sags! im now seeing a lot of this

Steve Roofer right I see what you mean, to be honest the ones I see getting fitted are probably skipping the vapour barrier then maybe, as I get to see them put the ply which has the insulation attached to it, not sure if the layers between this? Thanks

You're welcome to send me details and I can help you more but realistically you need all this worked out by an engineer I can't do that for you it's not part of my skill set size of Timber's and stress is an engineers job as regards warm roof cold roof always do a warm roof drop the roof detail down slightly if you have to. The height difference between a true warm roof and a true cold roof is so minimal I don't understand why people keep choosing Cold roofs

vandalstookthehandle c

Best thing I can say is contact S and D timber in Kenton Harrow, get all the materials there at unbeliever prices. For a new flat roof, you wont to be using a minimum of 100mm flat roof insulation with a good continuous vapour control layer under it. Don't use any insulation that has silver foil on both sides always use a separate vaper control layer and tissue faced insulation fixed with thermally broken fixings. You can email me for a list of suppliers, however, I ask for a donation to charity for the info www.justgiving.com/fundraising/roofing?newPage=True

The vapour barrier we use on all of our warm flat roofs is foil and tar on a role laid out over a sub decking to form a continues layer, if screws are used to fix down other layers penetrations tar-up and self seal however now the trend is to glue down everything.

Steve Roofer Thanks Steve that makes sense, I just watched your latest vid with glueing great thanks.

Well, that is a very good question and theoretically no because you have got a good favour Beria down below and they'll be no vapour or moisture in the roof buildup. However, in my own personal view as Belton braces, theoretically you could form a cold roof over the warm roof, so that if there was any vapour that got into the roof buildup it could get out that's a real good solid build up then but obviously cost lots of money and takes up more. Space

Yes Sketchup Yes you can use the old tar based roof as the vapor barrier If you dont open the roof you will have to remove the gutter board to access the area Was in chicargo last year and will be again this year

+Steve Roofer Ok Steve - Finally going through with this project. After much review of videos on the subject (mostly yours - Thanks) I have a 1915 low slope flat roof with (brick) parapets on 3 sides (open on lower side). I've decided to tear off the 1/2" - 2" multi-layer mess - down to the deck boards. I did a 1' x 1' 'biopsy' at the top parapet edge and the decking boards/planks look ok so far. Also, looks like they used felt over the decking - so hopefully tear-off will go as well as it can go. I'm going to be using (2) 2 1/2" staggered polyiso layers and a 1/2" high density polyiso on top (for walking) - all covered with 60mil EPDM. All of the polyiso is 'fiber-glass' faced on both sides. (Hunter Panels). The polyIso will create a R30.7 barrier. Since I have to tear out the ceilings inside anyway, I'll probably be adding a heavy layer of blown in cellulose around the perimeter to help avoid condensation at the brick wall underneath - and, as I understand, cellulose can hold and dissipate small amounts of temporary moisture level peaks. My only question (i hope) is the vapor barrier (or air barrier?) between the decking and the polyiso. Do I really want a water trap underneath the polyiso ? I'm a bit wary of capturing trace amounts of moisture from above and pooling them at the deck board level. I've read that the layered polyiso will mitigate most upward moving moisture ? Yet I see the moisture barrier used often ? Anyway to make this a simpler proposition and alleviate my concerns ? Thanks for all your help and the great videos and Sketchup models.

The VCL gos on the decking under the insulation, any moisture now under the VCL is in the room below and away from any cold spots or thermal bridging and therefor not a problem.

Fixings www.fixfast.co/fastener-systems/fr_globaltubewashers.php Vapour barrier instar-uk.co.uk/products/elotene-dsn-self-adhesive-vapour-barrier/ Insulation 120mm Recticell Powerdeck F 1200 x 600 We sometimes glue the flat roof insulation down The fixings go into the roof decking. SIG ( sheffield insulation also do vapor control layer that similar but more expensive expect to pay between £5 and £8 M2 Its not cheep

The answer to that is yes it is in good condition you need to go around the perimeter and put an up stand on and then put more fill up the up stand so that the insulation sits inside a framework that has made the barrier under it and around the four sides

Yes, absolutely in about three weeks time I will do a video on downlights and ceiling

@@SteveRoofer Many thanks Steve. I’m an electrician so will be interested to see this 👍🏻

Everything has to be fixed down with thermally broken fixings. The fixings go right through the top layer into the bottom layer and into the joists

No as its a warm roof all the insulation is on top. If you add insulation between the rafters, you can lower the duew point and could cause problems

@@SteveRoofer Thank you Steve. Much appreciated!

No but if you want to send me info ill have a look and make some suggestions

Not ideally - it could sweat internally and you may block the ventilation.

Make a donation to my help for hero's pages www.justgiving.com/roofing?newPage=True then send through all info on your warm flat roof and I will send you back a video explaining hat I would do

No not successfully if you took the ceiling down and looked up the joists are in the way. if you put some sort of plastic over the joists and across the insulation you have locked he joists outside of the VCL and that's not a good thing to do. However, it's probably better than doing nothing if you have a problem. Its all down to cost

Absolutely awful I can't understand how that's gonna work?

I forgot to mention that neither of houses in my neighbourhood have ventilation mushrooms and the height of my roof and their is very similar so I assume they have similar construction.

There is not a roof insulation on the market that has a build in VCL vapour control layer. There is roof insulation that has silver foil on it that the manufacturer's when arsked will say that you can use as a VCL but its not there to do that. A vapour control layer should be continues if you use sheet insulation how will you make it continues when you can't get to the side thats down against the ceiling.?

+Brighton Squash Club Warm or cold roof you shouldn't have drafts. with a warm roof you should be able to remove the ceiling and live with the timbers exposed as the space between them is supposed to be the same temp as the room below "a warm space" Yes we come across this problem all the time and yes insulation to the soffits is one of the problems.

+Brighton Squash Club the joist end voids should be infilled with insulation and sealed

+gareth chapman yes correct

Some manufacturers of insulation suggest that you can put the soft insulation directly over the joists that are spaced at 400mm however we find that this makes the roof bounce and is not that good . We place 18mm T+G OSB over the joists then we put the VCL then the Insuation Then more 18mm OSB then screw the thing togther using thermaly broken fixings then add the flat roof waterproofing materials.

Steve Roofer how do you screw it all together without piercing the vapour barrier?

You pierce it, Its so over-specified that even with leakage from the piercing its still over the corect specification.

In TV

New information suggests that there should not be a second deck on a warm roof. You are quite correct, the second deck is above the vapour control barrier and if vapour was to collect it could rot (interstitial condensation). Everything below the Vapour Control Layer (VCL) is internal, and is therefore subject to internal temperatures, with no risk of interstitial condensation and no need for ventilation. Above the VCL in the sandwich of insulation and roof membrane, there is a risk of interstitial condensation, this risk is reduced further by having a roofing membrane that has a lesser, or equal, resistance to vapour. If you start with a VCL that is of poor quality, don't fit it correctly, don't seal all the joints and don't seal it to the perimeter, then puncture it with fixings, its vapour resistance will be dramatically reduced. Start with a VCL that is of high specification and fix it correctly, and you should end up with an excellent VCL that also acts as an Air and Vapour Control Layer (AVCL), and should be equal to or above vapour resistance of the chosen roof membrane. The vapour permeability of most roofing materials on the market is hidden deep down in their specifications, almost impossible to find. I have never had a roof design given to me that has taken the above into consideration when specifying materials to be used on a flat roof. Always use the best VCL at the bottom, make sure that all materials used above are vapour 'open' (can breathe) and don't use foil-faced insulation in your roof buildup.

@@SteveRoofer Thanks Steve that's very helpful. The vapour control layer is also already laid but the ceiling below hasn't been slabbed yet. Any benefit to putting another VCL above the slab and below the joists leaving an air gap there (or filling it with insulation) or does just potentially lead to the same problem for the lower deck layer?

@@89feighery Unfortunately I don't know

I’d osb over the isolation then fiberglass

Sanafil is extremely good but like all things has to be installed correctly. it's good looking but expensive.

@@SteveRoofer Thank you for the quick reply.

You have to look at things like this all materials will allow the vaper to bass though. Some have better quality than others We use stronger AVCL air vapour control layers in the correct place thus forming a barrier, moisture that penetrates though can then work its way out as thematically the materials above are more open and moisture below is below and inside the property thus in harmony with the internal environment

No venting in a warm roof and no venting needed in soffits. Make sure that there is no moment of air from the outside to the roof void of a warm roof. Think of it like this internal spaces and external spaces Internal spaces such as bedroom living-rooms are only vented by people opening doors and windows, we heat internal spaces. External spaces such as garden sheds garages and loft areas are normally very well vented because of gaps and we are not bothered because we don't heat them. So with a warm roof construction everything under the insulation is internal and therefore we don't vent moisture levels will be the same as the room below as the cavity below the roof is in fact internal part of the room below remove the ceiling if you wish its only decorative.

Thanks for your quick reply Steve. Would it cause a problem if the soffit is vented ???

Only if you haven't sealed off this area to the area under the warm roof, you also need to make sure that the thermal properties of what you have used to seal the area with match one of the two elements. The flat roof or the wall if its weaker then you may get some cold bridging.

+Steve Roofer Thank for the reply Steve , would you get condensation forming below the flat roof ?? . Would it be better to seal the vents ??

If the vents are not venting the roof and only venting the soffit boards keep or remove up to you it will make no difference. If the vents are venting the flat roof condensation to the underside of the warm roof could happen if all conditions were in place, however its unlikely as the underside of the warm roof is warm so moist air will not condense onto it. Where the cold external air is getting in will be colder and you will get condensation around that area. Also you have completely lost the benefit of your warm roof, think of it like this. When you get in bed and you put your quilt over you, you wanted it to keep you warm so you tuck it in around the sides if you don't it doesn't matter how good the quilt is you will always be cold. So basically your warm roof is doing nothing just sitting floating on top of your joists. You must make sure that it is airtight and interrelated all of the way down to the next thermal element.

+Keith McManus When we do warm roofs we alway use 18mm T+G OSB decking under the warm roof insulation and the same over. It may cost more for the T+G but it's a lot easier to install and gives a better finish to the roof.

@@SteveRoofer does putting osb above insulation not turn it into a cold roof?

@@coops6621 No if its a cold roof its vented if its a warm roof there is no venting and you can put whatever you want on top

@@SteveRoofer is it not possible for any condensation reaching that top OSB layer?

@@coops6621 Yes in my view I think it will that's why the roofing membrane above needs to be as open to moisture passing through it as posable

1 in 40 to achieve 1 in 80

Its got to be warm roofs all day long

@@SteveRoofer Thanks mate. I've watched about 10 of your videos so far and figured you'd say that, just wanted to be sure 💪 Thanks for all the informative content

+Dee “RemixDrummer” Rythmist The vapor control layer we use on all of our warm roofs is a sticky back tar and foil materials, there are several supplier of a similar material Visqueen is one and www.rubber4roofs.co.uk do another.

+Steve Roofer I posted the message 6 months ago and now you reply. I even called you and you didnt wanna bloody help. time waster

Yes they work if fitted correctly

I don't understand what you mean about the steel panels can you elaborate?