Roofing felt for shed - nails or adhesive?

[Lobster]

I'm replacing the knackered felt on my shed roof - sloped roof with an apex, and the felt will go on as four strips, lengthwise.

So I fit the 'lower' lengths first, ie above the eaves, and these will be nailed down obviously. Then the 'upper' lengths go on, overlapping the lower lengths by 2-3 inches and covering the nail heads. Question - should this overlap be fixed using just felt adhesive, or with nails (or with both?) Have googled a bit about this and all three permutations crop up and am not sure what;s for the best. I'm concerned that adhesive alone won't hold the felt down and it will eventually succumb to wind; however if I nail it then isn't that introducing a water track into the roof timbers?

Thanks for any thoughts David

[Tim Watts]

Lobster wibbled on Thursday 17 June 2010 09:33

No nails, loads of gloop - is how I did it. Nails just around the vertical edges (and some gloop too).

BTW - if you use as much gloop as I did, sheet the shed contents, it will drip through. But the felt didn;t come off and we get some pretty high winds here at times.

Have you considered torch on felt - some here have used it and report excellent results?

[Man at B&Q]

I would use the Wickes self adhesive system, having used it to refelt a flat roofed porch.

MBQ

[John Rumm]

Lower first - so the higher ones overlap over the lower.

If nailing, then you really need *three* layers for a proper job. A hessian reinforced nailed layer - large clout nails in a random pattern all over on a 6" spacing or there abouts. Then a fully bonded underlay felt, then your top coat felt. Having done my first workshop like this, I concluded that it worked very well, but was a PITA and very slow to do.

Much *much* simpler, is get a rubberised torch on felt - two layers, one undercoat, and one top coat. Large f'off blowtorch - roll up the precut felt, position on the roof and torch it as you unroll it. Sticks like the proverbial to a blanket. Then do the top coat. The top coat has a joining strip (about 4" of adhesive facing upwards and no chippings), which you align with the overlap. This forms a very good seal between the sheets.

[NT]

Bitumen in solvent's pretty good. Nails do lift and let water in.

NT

[brass monkey]

I used adhesive but how about nails and gunge over the top of each?

[Lobster]

Thanks, all. Reckon I'll go for the adhesive-only based solution then... I'm sure the torch-on solution would be optimum, but in my case the shed is only an old, pretty knackered garden one TBH and I don't think worth spending much effort or dosh on; this is just a way of wringing out just few more years of life, using some felt I already have 'in stock'!

David

[Dave Liquorice]

No gloop, just nails here.

At least a 6" overlap. Top edge of underlying sheet nailed every 6" or so. Bottom edge of top sheet nailed every 2". 1/2" hot dip galvanised clouts (might have been 3/4"). Doesn't leak the felt seals around the nails, haven't had the felt rip through or nails come loose.

So do we, ordinary 8 x 6 garden shed. The orginal roof (2 sheets of

3/4" OSB plus a bit) was lifted off as unit and deposited 30 odd yards away having cleared a 6' wall 10 yards from the shed and nearly clearing a 4' one at 30 yards. A few years later the shed was empty after being reclad and it was rolled, as unit, up against the wall the roof cleared.

shed has now been fixed to the ground in each corner with 3cm square stake driven in as far as possible (18" to 2') and bolted through to the shed frame. It hasn't moved since and niether has the the felt come off...

[John Rumm]

I should have said felt + glue cost more than just torch on felt!

If you want a quick fix, just torch on a top coat over whatever is there.

[NT]

Where are you getting cheap torchable? Wickes felt is only =A313 for the grotty stuff, and 5.99 for enough bitumen

[John Rumm]

I pay about £27 for 4mm SBS torch on usually[1]. Felt at £13 a roll sounds like crappy 1 or 2mm shed felt - which lasts a couple of years if you are lucky. The glue goes fairly fast as well if doing nail prep and a couple of layers (I think I used about 10L for about 16m^2 of roof.

[1] Last lot I got from Ashphaltic roofing - however that was not their list price which was something silly like £54, buy a few rolls and the price tumbles - then keep the receipt and make sure they always match their better price in future.

[NT]

yes, better stuff twice that

might try that next time, cheers

NT

[Tim Watts]

John Rumm wibbled on Thursday 17 June 2010 12:18

Just out of interest - how f'off?

Largest on a can, or something that needs a full-on caravan tank of propane and the torch is on a long rubber hose?

[John Rumm]

Well the list price is getting on for twice that - (4mm is the better stuff, the cheaper stuff is 2mm usually)

It definitely works - a mate of mine was slapping a layer over his existing flat roofs - so we ordered something like 25 rolls. And got a decent price. He went back for an additional roll and got charged full whack for it. So next time I went there I took both receipts and queried it and promptly got a refund for the difference.

[John Rumm]

I use one of:

the main attraction of that is comfort working - you can stand and kick the roll in front of you as you move forward (you play the heat over top and leading edge of the roll and the surface at the same time so they both go together hot).

You can easily get enough heat out of a smaller torch with a large end on it. Say something like:

this is handy for edges, and drips etc, it would not be a easy to use for larger areas.

I use the smaller torch on the dinky 4.7 kg propane bottles. The big one can run at up to 36kW IIRC, so that would probably be better on a 12kg tank or larger unless you are only doing a couple of rolls.

[Tim Watts]

John Rumm wibbled on Friday 18 June 2010 14:54

Thanks John. The top one looks the sort of beastie I've seen roofers using.

For a small shed I could manage with the 2nd.

[John Rumm]

Yup, with a wide nozel on the end it will produce the sort of flame you need - you just need to stoop over (or work on your knees) to use it.

Avoid the technique demonstrated by a mate of mine though. He was putting a torch on felt coving on a prefab/mobile home roof, wearing light weight shoes and frayed jeans. He has got aformentioned f'off blow torch in one hand, and was holding something else in the other. He was getting into a spot of bother when he worked out the ill fitting jeans were slowly falling down as he walked forward. In an effort to pull them up he manage to set fire to the frayed ends of the legs! Then begins the panic "mooning dance" for the spectators! He passed the lit torch to the lass who was helping him on the roof, but basically she was too convulsed with laughter to be much further help.