FLAT ROOF - ONE LAYER OF FELT?

[artfuldodger128]

I am planning to replace my existing flat roof.

I bought this Protect A1 underlay sheet from Screwfix which claims to be better than traditional felt underlay. The plan is to lay a sheet of this stuff (instead of the normal 2 layers of underlay) and have a capsheet on top.

Will this work?

Further, I am also very wary of moisture coming through over time. Would it be possible to place a damp-proof membrane underneath the capsheet using felt adhesive?

Any advice will be appreciated.

 

[Deluks]

Keep your receipt! I believe the A1 is meant to go under tiles on a pitched roof. AFAIK Screwfix don't sell any flat roofing materials.

Felt adhesive should only be used on felt, a good quality felt is what's needed, and ideally 3 layers. How big an area do you have to cover?

 

[artfuldodger128]

Many thanks for the response.

The flat roof is about 2m x 2m. The reason I am looking for alternatives is that I dont feel felt will last. I had a guy who did some work on the same flat roof about 3yrs ago, and water has penetrated onto the board and now I have to replace the whole lot! And I paid a lot of money for it as well!

Are there alternatives other than felt?

Also, can you respond on the point I had on the damp proof membrane? Cheers.

 

[^woody^]

Felt, done properly should last more than 10 and up to 25 years in the right place.

Bitumen felt is a layer system. One layer is bonded to the deck and then another one or two laid on that. You can't fit a DPM on the deck first, and there is no advantage in it in any case.

Water does not penetrate felt over time. It gets in if a joint opens, or the felt is punctured.

Don't let that cowboy job put you off felt. Done right, it will last.

And alternative is rubber/epdm cover. Lots of posts on here about it

 

[datarebal]

2 mtr x 2mtr should not have cost much.. certainly not worth faffing around with cold adhesives etc

 

[vinty]

I am planning to replace my existing flat roof.

I bought this Protect A1 underlay sheet from Screwfix which claims to be better than traditional felt underlay. The plan is to lay a sheet of this stuff (instead of the normal 2 layers of underlay) and have a capsheet on top.

Will this work?

Further, I am also very wary of moisture coming through over time. Would it be possible to place a damp-proof membrane underneath the capsheet using felt adhesive?

Any advice will be appreciated.

use torch on felt, you can get 2mm underlay then a layer of 4mm torch on cap sheet on top, the felt itself is a form of damproof membrane. be careful when using a cas torch.