expanding foam with ultra-fine nozzle?

Is it possible to use a silicone mastic with a fine nozzle end?

Cash

So along the sheets not up the corrugations where they rest on the wall plate? I'm surprised water is getting in there, have the sheets got the correct overlap? Two full crests IIRC.

Foam isn't really the right stuff, from a can it's open not closed cell so water will get through it. As some one else said a good bead of exterior grade silicone along the edge of the sheet is probably you best bet, having cleaned/removed any loose material first.

If the sheets are just nailed on is there any sealing washer under the nail heads?

JakeD scribbled...

I'd avoid foam, it will continue expanding for some time - as I know to my cost- and could split the brittle asbestos sheets.

Depends whether it forms closed or open cells when it sets. If the latter, then don't do it - it will soak up water like a sponge.

"Cash" wrote in news:bi19b3FoichU1 @mid.individual.net:

I wondered about that. I can give it a try.

However, now I have inspected the underside of the asbestos idn broad daylight, it looks as though the moisture is actually bleeding through the affected sheets. Most of the sheets are impervious and dry on the underside. Just a couple of them seems to be allowing water to bleed through.

Any suggestions what I could paint onto the top sides of the sheets to waterproof them? Something clear, that won't colour the sheets would be ideal, because I don;t want the painted sheets to sook different from the reat, and the roof is too big to paint the whole lot. Would diluted PVA do it? Or is there something better?

Thanks to all respondees.

JD

"Dave Liquorice" wrote in news: snipped-for-privacy@srv1.howhill.co.uk:

They have the two-ridge overlap. However, I'm not sure hos much overlap they have londitudinally (if that's the right word)!

On closer examionation, it looks like water is bleeding through a couple of the sheets, as the look darker in color, and droplets of water can be seen on the underside of the ridges.

JD

Not sure PVA will put up with repeated wet dry cycles will it?

How about something like

Or cheaper (not as good, but maybe good enough?)

Darren

JakeD,

Providing there are no cracks in the sheets, you could spray or brush on a clear silicone waterproof coating over the whole roof which may help.

My advice though (funds permitting) would be to re-roof with Colour Steel sheets (can be laid on top of the old sheets[1]) to give long-lasting weatherproofing[2] as asbestos sheets are a beggar to seal once they become porus[3].

Have you checked the sealing washers under the fixing to see if they are doing their job as this could possibly be the cause of the leak - especially in heavy rain?

Cash

Some of the foam guns come with a narrow conical nozzle you can put on the end of the gun (I know the Bond-It Teflon coated one does, actually I wish you could buy extra ones as they wear out).

-- Andy Burns

On Friday 27 December 2013 08:19 snipped-for-privacy@gmail.com wrote in uk.d-i-y:

And one-shot cans (non gun type) tend to have smaller stubes supplied .

It doesn't expand much but how about the space filling polyurethane glue that is officially intended for exterior woodwork repairs?

Wear gloves and eye protection when working with it - it is extremely high tack, water tolerant and somewhat flexible when cured!

snipped-for-privacy@auk.kent.ac.uk (D.M.Chapman) wrote in news:l9i4qq$8tl$ snipped-for-privacy@dont-email.me:

Thank you for these suggestions. The last link above looks like good value. I'm always a bit wary of buying products where they don't specify the ingredients (in case I'm just buying diluted PVA, but at double the price).

Can anyone else comment of the suitability of PVA solution and/or Everbuild Waterseal and/or Thompson's Waterseal?

JD

"Cash" wrote in news: snipped-for-privacy@mid.individual.net:

Yes, the washers seem okay. I think it's just a couple of the 30-odd sheets that are letting rainwater bleed through, so I'd like to try the most affordable-but-effective clear liquid sealant first, before going for anything more expensive. Thompsons Waterseal or Everbuld Waterseal (are they the same thing?) look interesting. Has anyone used these products and found them effective and long-lasting for exterior use?

Many thanks,

JD

I think for £12 you may as well just have a go & see if it sorts the prob lem?

Jim K

Jim K wrote in news: snipped-for-privacy@googlegroups.com:

That may be the thing to do, but I thought I'd ckeck first - in case, say, anyone has found the stuff to have undesirable effects on asbestos or whatever. In the field of DIY and building materials, I've learned to try and avoid taking anything for granted.

JD

Take care if walking on an asbestos roof.

I used to be able to walk on my asbestos garage roof then, ten years later, I stepped on it and went straight through it and ended up inside the garage!

That may be the thing to do, but I thought I'd ckeck first - in case, say, anyone has found the stuff to have undesirable effects on asbestos or whate ver. In the field of DIY and building materials, I've learned to try and av oid taking anything for granted.

JD

End quote/

Judicious googling will alert you to any obvious pitfalls with a plan. Rely ing too much on stuff on here without further checks is inept if not stupid sometimes.... Jim K

Moral of the story here is *ALWAYS* use a duckboard when working/walking on asbstos cement roofs (or similar, inc. corrugated steel ones) - whether new or old!

It's a hell of a learning curve when you fall through one.;-)

Cash