bmj1

Mannok do an insulated plasterboard that is 17mm PIR + 9.5mm plasterboard. Works a treat. Used it on our project.

We've done the same.

I've had to solve this problem for cavity walls... if you want something for your walls, look at this: https://www.mannokbuild.com/pir-insulation/mannok-therm-laminate-kraft-mlk/ Insulated plasterboard, you choose from 17mm of PIR + 9.5mm plasterboard (26.5mm total), up to whatever thickness you want. Has paper facing for dot + dab, for ease of application.

You need to protect yourself in case your asset burns down in a freak accident, etc. For me, that's the biggest reason to have your own insurance

And all the wiring and downlights is below the VCL?

Have you looked at https://www.velux.co.uk/products/sun-tunnels This might get you out of a jam here ?

What about doing a skylight instead?

How big is the window? You need to check the fire regs here with your building control/architect. If on the boundary you might not be allowed to have it openable at all.

1. Plywood deck 2. Sarnavap 500E 3. Insulation 150mm 4. Additional deck 5. Liquid waterproofing finish Question: does it matter if the insulation is tissue facing or foil facing ?

Hi all, We're looking at a balanced flue/gas fire system, to sit below our side extension, which as a flat roof immediately above it (I understand an open gas fire is not possible as no chimney). We'll be sealing the roof in the next couple of weeks (deck/VCL/insulation/deck/liquid waterproofing layer). What's the best way of doing the flue penetration through the flat roof ? Do I need the specific first fix items from the fireplace company now, or can we just run a duct for it - and if so - what size duct would make sense ? Thank you so much for your kind advice.

Is a flat roof involved? This is the one area I got burned on when our main contractor did the same..

Or could use this for our ceiling, below the joists ? (Taking special care to seal any penetrations)

Or could I apply the VCL from underneath the joists? A bit more work, but feasible ?!

Just came across this thread: VCL paint from below as another possibility?

Maybe... What kind of structural problems are you concerned about ? If the whole condensation issue is localised and contained above the deck I'm not sure what issues you foresee?

Polythene plastic loose laid was used instead of specified VCL. Spoke to a specialist flat roofing company today who advised me it's just a matter of time until it fails... But welcome alternative thoughts !

Hi all, I've got a newly built warm flat roof that I've been advised is likely to fail at some point over the next few years due to an error in the build-up / interstitial condensation. Instead of replacing it today, I'd prefer to try and get a few years of use out of it, and rebuild it down the road when finances are hopefully a bit looser.. Any thoughts on some kind of moisture meter I could install, and where I should locate it ? I.e. would between the joists be sufficient ? We'll be running services between the joists and then plaster-boarding below

Thanks for the feedback.. It's dot and dab, so I've assumed some kind of gap behind the blockwork. Does that make sense ? I don't want to go so high with the thickness, to conserve floorspace ! So to confirm, no need to worry about a VCL, even if the insulated plasterboard has no foil component ?

Not committed, looking at 17mm PIR bonded to 9.5mm plasterboard, as the insulated plasterboard. I'm a little nervous about the dew point also. And I do think we have to assume there will be some gaps between the rockwool locally in a few areas... Does that make sense ?

Ok thank you. So no risk of interstitial condensation?

Wall build up 100mm Brick 50mm cavity 100mm rockwool slabs 100mm concrete block Insulated plasterboard (not yet built) Does the insulated plasterboard require an integrated VCL ? (assume dot + dabbed).

I looked at this product myself but couldn't find third party verification/certification of the claimed conductivity.

Exactly. The other key point of aerogel is that it is vapour permeable, making it suitable for retrofit in older buildings. Having looked at aerogel for wall looking, we're now making use of an insulated plasterboard with just 17mm of PIR bonded to 9.5mm of plasterboard.

Can you provide more information on the problem you are trying to solve?

Okay, I think this is very bad, but want to get opinions: We have a finished flat roof: 100mm warm deck above, and for some reason, 25mm between the joists ?! The insulation between doesn't appear to be pressed up tight against the plywood above (which I understand is the thing to do when doing this), but instead, there is a gap due to the piece of wood running across above the joists I'm concerned about interstitial condensation Is the only sensible option is to remove the 25mm insulation between, and live with 100mm insulation above... and make up on the SAP elsewhere ?