UKC

Brush it clean (cough) and slap some aquapol on it?

In reply to iksander:

I think its only dangerous when broken up which creates small particles. So what ever it is, wear a good mask!

In reply to iksander: If you can get plastic corrugate the same pitch, I would thing a plastic patch would be safest. You could slap it on with plenty of sealant and you wouldn't need to disturb the asbestos.

In reply to iksander:

I've fixed a few cracked roofs like this and tried different sealants.

If the problem is tiny cracks (can you just see daylight from beneath?) then use a wire brush and then this:

https://www.google.co.uk/shopping/product/15694849585374249078?q=roof+repai...

Sticks like the proverbial and never really sets so it doesn't peel off after 6 months. Smear thin layer and work into the cracks and then another neat layer to cover it.

If your roof is anything like our garage the problem is not enough asbestos! When its use to make corrugated concrete less brittle was restricted they tried reformulating but the asbestos-free ones were never quite as good.

In reply to iksander:

Brushing it will also disturb a surprising amount of fibres (as proven by some recent airtests I've been privy to).

If you're cleaning it from above give it a wet down with water/pva (3/1) mix to help bind fibres better, then clean and double bag the waste (Technically it's classed as "contaminated"), then I'd see about getting a matching profile pvc sheet and try and bed it under the next sheet up with a decent lap, before fixing it down. If you're fixing the bottom of the pvc sheet to the next sheet down I'd slap some nice thick wall paper paste down when you're drilling (again for fibres) and you should be golden.

If you can only fix it from below, I'd still wet it down, you're not going to be able to get a sheet in most likely so the lead sealant is probably your best bet.

I'd also see about getting a disposable overall on (guidelines say type 5/6, about £4 a time probably) an FFP3 facemask (the cheaper ones let everything through) and a set of disposable gloves, if its Asbestos Cement Board it's probably Chrysotile (classed as "white" but its got bog all to do with its colour), this is relatively benign by asbestos standards but can still cause harm to both you and others so not worth taking a risk.