Flat roof material

I used EPDM rubber when I re-did all the flat roofs here about 9 years ago, the rubber has collected some algae, but that's about all, apart from having to give the PVC edging a damned good rub-down with this stuff a couple of years back.

Probably means the only way he knows how to do. Rigid materials last far longer.

NT

EPDM rubber seems to be the way to go these days. It needs different adhesives, flashings and edging extrusions etc so some roofers might prefer to stick with the processes they are familiar with ie best for them, not necessarily best for you.

I've done one small flat roof as DIY but only been in situ for a few months - too early to tell. Rubber has 30 year warranty.

I went with felt because my roofer (who did a superb job on the tiling) did not know any other, except having a bad experience patching someone else's fibreglass roof that sprang a leak (a crack).

The felt was not planned but we discovered the deck was shot so I had to go with a rapid replacement.

Next time (which is probably 10-15 years away) I will be ready to consider a more permanent material. Probably sheet metal, provided it is not too noisy in the rain. Hardly matters what it looks like, no one can see it except Google ;0

I put an EDPM rubber membrane under the green roof on our shed. Been up about 6 years now with no problems. (Well protected from UV of course, with six inches of green roof on top.)

I have a felted 'flat' (except it's not flat) roof here - where the attic room was extended to the rear. So something like 6 x 5 metres in size. Properly made with slight slopes to the centre, which in turn slopes to the edge. And decent marine ply underneath.

This was constructed some 25 years ago.

Any roof which is badly constructed can give problems. And flat roofs often are as it takes more time during construction to provide a slight fall.

I'm quite willing to accept there are better materials than a decent felt

- but not on the basis of it having lasted a few years. ;-)

Sheet metal /is/ noisy in the rain. It never bothered me though. Its handy to have advance warning of rain, the first 2 drops and you know its about to rain.

NT

Well, this will have 3/4" OSB and 100mm celotex then PB between it and my ears - so I wonder if it will still make any noise then?

Yes. My workshop pitched roof is a metal sandwich with 75mm PIR foam. Even light rain can be heard.

I have concrete.

Noisy as anything in heavy rain.

Owain

Thank you - that's worth knowing...

So - what *is* the best material?

EDPM seems one of the better ones, as long as no one gets ham fisted with it later (dropping sharp pointy things).

Fibreglass seems to have problems cracking.

Metal is noisy.

Not sure there's any such thing, all the good ones have their strengths & weaknesses. On a flat roof of course you're a long way from best roofing practice whatever you put on it.

That's ok. Its very ugly when rusty though

NT

Well, I was thinking ali rather than iron...

Or copper, but some pikey would nick it.

Layer of roadstone over your preferred membrane? Helps fire resistance.

I don't know if the following applies to all closed-cell foams, but I found that a rubber band round a block of polystyrene foam was very loud when twanged, as if all the little voids acted as drums (you can try this at home!). If Celotex is the same it'll transmit the sound.

Zinc.

Comes on a roll with two blokes to fit it:-)

I am shortly visiting a friend who has a recent *grand design* with a relatively shallow pitch zinc roof. I'll ask about rain noise.

Fibreglass. Roofers don't generally understand it so don't use it. Also, unlike felt, it doesn't give them a job for life.

Properly done it lasts for a very long time and will not crack. Cracking is caused by poor installation - usually too much resin and too little glass mat or trying to do the roof with just one layer of glass. It is easy to mould around pipes, drains etc and more than strong enough to walk on once cured. If you do manage to damage it it can easily be repaired and the repair is as strong as the original.

A fibreglass flat roof on an garage I helped with 40 years ago is still going strong and has never needed repair.

Peter Parry posted

Both the roofers who have been round so far have dissed fibreglass on the grounds that it can't cope with movement in the structure.

Thanks.

This is a flat roof so pitch is just a very few degrees.