Roofing felt questions.

[T i m]

Hi all,

My old 8x4 shed / mini workshop (18th birthday present) is still in Mums back garden and a few years back a mate (with me helping) replaced the (flat / sloping, whatever that's called) stock roof with a larger (greater overlap on the front / door end) OSB panels.

We felted it from bottom to top, felt nails ever few inches on the overlaps and round the edges and the sides had fascias screwed over them.

Mum phoned during the recent storm to say that most of the top strip had come off and in following winds, as did the rest of that strip later on.

Now, there was no adhesive visible and I can't remember it being used so what might have allowed it to pull off so cleanly / completely?

All the nails are still there (felt ripped round), as are the fascias that are trapping the top strip on 3 sides so it really has been ripped off?

I was wondering if it was being flexed (sucked) up and down in the middle of the strip it might have worked hardened the edges where it goes over the edges and behind the fascias and that's where it initially let go?

So, when we get a mo (and on a warm dry windless day) I intend to remove the fascias (screwed on), all the nails on the overlap and re felt and nail the top strip, but should I also glue it on?

Cheers, T i m

[The Marquis Saint Evremonde]

T i m [e-mail]> posted

I had the same problem in the December gales. I stuck the new felt down with Everbuild Black Jack bitumen felt adhesive, painted onto the (carefully cleaned) wooden roof panels.

I had to wait eight weeks for a dry windless day :)

[Davey]

That sounds like the instructions on some lawn weedkiller my Dad bought years ago, which included the instructions to "apply 5 hours after and five hours before rain".

I believe he just did the best he could.

[Bob Minchin]

Felt is a waste of time and effort. Use EPDM and do it once only

[harry]

If you want to secure roofing felt, do it by nailing battens on top. (Running from apex to eaves.) Paint the underside of the battens with bitumous paint and nailon while wet.

[PeterC]

The only felt that I've found to be strong was one with glass fibre in it. The ordinary felt could be torn with thumb and 2 fingers of one hand; the g-f felt I couldn't tear. Got it from a proper roofers place near Doncaster.

[tabbypurr]

It's incomaptible with bitumen though, so you generally have to replace the deck as well. Steel is cheaper IIRC.

NT

[tabbypurr]

I've seen the results of that, so would not recommend it. Perhaps in severe wind areas where risk of rip-off exceeds risk of the batten nails splitting the felt.

NT

[ss]

I done that 6 years back and after it was installed went around and used this for around the felt nails and the joints, been good since. It seals the joints and stops the wind getting underneath the felt.

[T i m]

On Sun, 24 Mar 2019 17:48:54 +0000, Bob Minchin [e-mail] wrote: <snip>

Well, I've had the shed over 45 years and I can't remember having to re-felt it very often?

A quick check, 3 x 4m of 1.2mm is around £100, plus adhesive, carriage and Vat etc.

An advantage looks like it's reasonably easy to apply and durable so I might check it out ...

On similar lines I was thinking of laying some woven fibreglass mat directly over the OSB?

Cheers, T i m

[harry]

It's normal practice.

[Brian Gaff]

Well it tends to go very brittle where its bent so any corners not covered by any baton or whatever tends to rip letting the air get underneath and it gradually gets worse in height winds.

I cannot say I've ever glued it on though. Might be a pig to remove when you have to if you do! Brian

[Kipper at sea]

The shed felt must have been cheap DIY thin felt. Try a good quality flat roof type from a roofing suppliers or builders merchant.

[tabbypurr]

Yes, and where it's not needed it causes roofing failures. Stick to high wind areas.

NT

[Rob Morley]

Two layers of chopped strand mat works well on OSB, you'll need a gel coat too.