Sorry to dig up an old thread, i have a new warm deck flat roof approx 60sqm with no expansion joints. The roof makes the most almighty banging noises in the morning when the sun heats up the roof and late afternoon throughout the night as the roof cools. It is horrific, i've seen many posts suggesting removal of the GRP roof in favour of EPDM. Has anyone done this and did it work?
Noise from GRP flat roof
- Thread starter ajs1954
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It would certainly work - EPDM is highly elastic, it def won’t make any noise.
The only thing I find on my garden office is on a hot summers day there’s a slight smell of burning rubber - and it gets chuffing hot in the sun
'removing grp' sounds easy....but it means either grinding it off (no guarantees that would silence it, the resin penetrates the osb) or ripping the osb up and replacing it, not easy if it's been screwed down and the heads are full of resin!
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Hello everyone I too have a grp driving me mad had it fitted 2021 the noise coming from the roof is horrendous booms cracks there seems to be a few all thermal related. October to March is the only time we have peace then the noise starts morning then the sun hits the front about 4 then the cooling down about 6 for 2 hours then silence it takes over your life
Ours is the same (approx 6x6m GRP warm roof built 2022). The expansion noise is horrendous.
I’d like to know what went wrong in the construction. Surely not all GRP roofs do this?
I am never getting a GRP roof again (or even any flat roof to be honest). Nightmare.
thanks. Yes, that would be one solution (or EPDM) - does stripping the GRP involve removing the whole deck (boards/insultion/boards) or can it just be mechanically stripped off the top layer?
Also - what is the proper way to make a GRP roof that doesn't have expansion problems? Why are so many roofers doing it the 'wrong' way?
Grinding GRP off is possible but very tedious and might not solve the problem (depends how deep into the OSB the resin has gone).
Usual problem is not fixing the deck securely to the joists.
Quick way to do an insulated flat roof is set the joists (or just reuse existing), chuck the sheets of PIR on top then fix the deck boards to the joists through the PIR boards with very long screws.
If the screws aren't long enough or miss the joist or only pick up an edge there will be an opportunity for flexing right there.
Even if the screws are done properly (min 40mm bite into joist) there is much reduced friction so the deck boards will still be able to move independently.
And then there is my pet theory about the temperature gradient when the underside of the deck boards isnt ventilated.
Usual problem is not fixing the deck securely to the joists.
Quick way to do an insulated flat roof is set the joists (or just reuse existing), chuck the sheets of PIR on top then fix the deck boards to the joists through the PIR boards with very long screws.
If the screws aren't long enough or miss the joist or only pick up an edge there will be an opportunity for flexing right there.
Even if the screws are done properly (min 40mm bite into joist) there is much reduced friction so the deck boards will still be able to move independently.
And then there is my pet theory about the temperature gradient when the underside of the deck boards isnt ventilated.
thanks oldbutnotdead - I suspect missing the joists or insufficient fixings is exactly what happened. These guys usually do cold roofs so I imagine they just don't have the experience to know how to do it properly (my mea culpa for choosing them).
What's your pet theory? You don't mean above the plasterboard and under the deck should be ventilated do you?
Consider.
18mm osb deck covered in grp in the sunlight.
On a cold roof that heat can reradiate both ways - back up into the sky or down into the roof space.
On a warm roof (with insulation hard up to the deckboards) very little heat can escape down into the roof space therefore the deck temperature will be higher than for a cold roof (given the same energy capture).
That's my pet theory anyway.
18mm osb deck covered in grp in the sunlight.
On a cold roof that heat can reradiate both ways - back up into the sky or down into the roof space.
On a warm roof (with insulation hard up to the deckboards) very little heat can escape down into the roof space therefore the deck temperature will be higher than for a cold roof (given the same energy capture).
That's my pet theory anyway.
So are you advocating that overall a cold roof is to be preferred?
Or is it that GRP isn't suitable for warm roofs?
I am wondering where to go next really with this roof of ours - rip it off in favour of a cold roof or replace with another warm roof (felt or EPDM)
Remember my warm roof theory is a theory, not proved.
I've only done cold roof GRP and all quite small (biggest about 10 sq m). No noise problems with any of them (mostly bay windows).
Big advantage of GRP is with fiddly shapes- on large surfaces EPDM is probably a better bet, GRP relies on totally solid deck, completely dry when resin applied, you have to apply the correct amount of resin (too little and you risk air pockets, too much and you can get cracks forming as it cures), you have to work every square inch of mat/laminate to avoid pinholes,
I've only done cold roof GRP and all quite small (biggest about 10 sq m). No noise problems with any of them (mostly bay windows).
Big advantage of GRP is with fiddly shapes- on large surfaces EPDM is probably a better bet, GRP relies on totally solid deck, completely dry when resin applied, you have to apply the correct amount of resin (too little and you risk air pockets, too much and you can get cracks forming as it cures), you have to work every square inch of mat/laminate to avoid pinholes,
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