Hi, I have a garage with an old corrugated asbestos roof. The roof has a number of small holes where the rain gets in. Also, a draught gets in through gaps where the sheets overlap. Would expanding foam be suitable to plug these gaps and holes?
Cheers,
Al
Al 1953 :
I don't know but faced with the same problem I used clear silicone sealant to good effect. It kept the rain out and it was inconspicuous.
Al 1953 wibbled on Saturday 27 March 2010 12:18
Yes, foam should work very well on the overlaps. For the holes, the foam willbe too exposed to the sun, which rots it. Silicon some patches of rubber or plastic or ali sheet over these could be one simple answer.
could be. Or use any frame sealer designed for exterior us, or even a mastic or putty.
Its only a hole, innit?
Dunno about expanding foam, I've avoided it since I made a mess all over the window frames.
I'd have a first try with the acrylic roof repair with fibres in it, that wickes sell, this deals with small gaps.
Next I'd look at hot melt on hi performance roofing felt. I've used this on an asbestos fibre garage roof where yobbos had through a brick through it, still good after 10+ years.
AJH
Read a couple of recent threads on asbestos and its hazards, particularly for roofing.
gets in through gaps
Squirty foam is great on the gaps in overlaps. However it has little strength and very poor UV resistance, so it's not good for holes. If you do use it for holes, you'll certainly need to cover the outside with something opaque, such as aluminum tape. or even thick aluminium foil (caterer's buffet trays, in my shed).
A better repair though might be more asbestos, such as offcuts of other sheets.
A really useful tube mastic here is the black very slow drying bituminous one from Wickes or Screwfix, sold as roof repair mastic. It's sticky, flexible, and it just doesn't care about water. You can seal wet boards, even while it's still raining.
Al 1953 pretended :
Ordinary mortar works well on the larger holes, if the panel is cleaned up a little first. Silicon frame sealant works well to stop both blown rain and drafts, if forced into the overlap from the inside. Sometimes it can help if the gap is prised apart gently to increase it, before pushing the sealant in.
The message from Al 1953 contains these words:
Expanding foam fine for along the edges of sheets if used from the inside.
For small holes, cracks etc. Any sort ofd scrim with several layers of thick bituminous paint. Stick it into the first layer and then paint over several times.
Which laps are the gaps in, bottom or side ?. Stitch bolts and plastic washers are used to fill old fixing holes.
Kipper at sea wrote in news: snipped-for-privacy@t23g2000yqt.googlegroups.com:
Thanks for the great suggestions, everyone. the gaps are at the overlaps, at the ends/bottoms of each sheet. I had to repair the roof using some corrugated asbestos that was slightly different "wavelength" to the original stuff... or maybe the original stuff had got flattened a bit over the years. So I have bigger gaps than I would have if the whole job had been done with identical sheets. Owing to a scarcity of spare sheets to affect the repair, I have ended up with only 4" overlaps down one strip of the roof. So the expanding foam will be particularly necessary, for stopping the wind blowing rain back in, under the overlaps.
Al
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