Oversheeting Asbestos Roofs (2023 Update)

[Autolycus]

While investigating the options for replacing the 35 sq metres of asbestos cement roof that blew away in Saturday's gale, I have discovered just how expensive asbestos disposal has become. One local firm has quoted £50 per sheet if I took it to them, or £850 for a skip. Derbyshire County council will only accept 2 square metres at a time at their sites.

I'm hoping the insurers (Zurich) will pay for the disposal of the smashed sheets and the remainder of that roof which is now in a precarious state, but I have another building of around 120 square metres which is structurally sound but has a number of leaks in its big-6 asbestos sheets as well as quite severe condensation problems on the underside of the roof. I don't relish removing the existing sheets, and I certainly don't relish paying for their disposal.

Does anyone have experience of "oversheeting" with steel, onduline, or other materials? I believe it can be done directly onto the sheets, having first removed all the nails, or onto battens.

[EricP]

Such is the hysteria that we now face for disposal of this simple mineral.

I look out of my window at acres of garage roofs covered in the stuff. I hope it lasts a bit longer.

[raden]

In message , Autolycus writes

Don't forget that with e.g. corrugated steel, you will be liable to get condensation from the roof dripping everywhere unless you have some cunning scheme to overcome this

[raden]

In message , EricP writes

I used to erect pre-fab concrete garages. Fixing the roof on entailed one being on top with a drill and screwdriver and one underneath holding the clips in an atmosphere thick with asbestos dust.

Of course, the danger depends on the type of asbestos , but I never see this mentioned

[Dave Stanton]

You wont!, it does'nt suit peoples interests to give all the facts. Same as mobile phones and all this talk of radiation, radio waves are a FORM of radiation, but the way the media present it, gives the impression of nuclear radiation !!.

Dave

[Mcluma]

You don't know how lucky you are m8

If you would have lifed in the Netherlands, Germany or the US, yo would't be able to gone have back in your house until it was cleare off the stuff and have given the all clearance

This stuff is dangerous, and get it out of your life sooner the latter, DO NOT LISTEN TO PEOPLE who don't see the danger of this stuff SCIENCE has come up to level with the danger of this stuff.

DO NOT TAKE ANY CHANCE

-- Mcluma

[Huge]

UN-altered REPRODUCTION and DISSEMINATION of this IMPORTANT information is ENCOURAGED.

[Grunff]

You are pretty clueless on the subject, and should avoid giving advice until you have read up on it.

[N. Thornton]

Fwom:Autolycus ( [e-mail])

local

sheets,

Maybe its time for the famous disposal trick? For those so desperately poor as to be unable to afford a skip, building materials can be put in domestic trash, a bit each week. Slowly it all goes away, free. Just bag it in small bags rather than rubble bags, carrier bags ideal.

Asbestos should be double wrapped in plastic before being landfilled, what the law says about putting it in the household trash I dont know, cant tell you.

But I cant see this being much of an issue, since your insurer will be liable for disposal anyway. Unless you decide to settle for cash and dispose as cheaply as poss.

Re your 2nd building, I presume cement sheet, which is what asbestos sheet is, could be cement lined to renovate it. Mixing fibres in for reinforcemenr would make it behave musch like the asbestos there already. Presumably one could make a good superstrong mix and trowel it thinly onto the asbestos already there? Certainly be a big cost saving.

Strong cement mix:

3:1 is ideal ratio for standar sand/cement only mix. Add pva for increased adhesion Add fibres for increased tensile strength and crack control Add extra fine non-organic silt as well to improve granule packing, thus increasing both comprssive and tensile strengths.

You could either treat the whole roof like this or just spot patch.

NT

[raden]

In message , Dave Stanton writes

So it's ... unclear radiation then

[Autolycus]

Assuming that by "cement lined" you don't mean trying to render the _underside_of corrugated sheet, three problems spring to mind:

Preparation of a moss and lichen-encrusted, slightly friable area of asbestos-cement sheet to accept a trowelled-on cementitious mix would be non-trivial: filling the troughs completely, and having say an inch of render above the peaks would require around 6 cubic metres of concrete - over 12 tonnes more load on the structure, and a hell of a lot of mixing and lifting; then, of course, if (when) any cracks do develop through thermal or structural movement, water could well run down the very corrugations that are leaking now.

I don't know whether the extra thickness would provide enough insulation to solve the condensation problem.

Not easy to spot patch _and_ profile it so water running from further up the roof doesn't pond in a corrugation - and there's still the preparation problem.

Thanks for the ideas - but I don't think we're there yet.

[N. Thornton]

Power wash it to get the bulk off, the PVA content in the mix should provide enough adhesion to deal with any remaining bits, and resolve the friability problem. Bear in mind the new stuff would only need to stick in patches for it to be fully successful.

concrete -

The original sheeting is 5mm thick: why ever would you want to put a couple of inches onto it? Thats a completely untenable idea, your structure will only take so much load.

A more sensible 5mm gets rid of that one.

You'd be replacing like with like, asbestos cement sheet with d-i-y asbestos cement replacement bedded onto asbestos cement sheet, so performance should be similar.

insulation

unlikely. That would need a bit of insulation if its a problem.

As long as the patches are trowelled so the leading edge is sloping slightly they should work ok, the slope at the patches will be very reduced of course, but as long as it doesnt slope the wrong way it should still function ok. Even horizontal will function.

not really

Maybe 'we' arent.

NT

[Christopher]

QUITE CLUE LESS !! iN aFRFICA i WORKED WITH BAGS OF LONG FIBER ASBESTOS AND I AM AHEATHY 87 TRS OLD. IT IS THE SHORT FIBER WHIC IS DANGEROUE BECAUSE IT IS LIKE TINY NEEDLES IN SHAPE.

[Brian Gaff]

What are you trying to say? Its got lost in the translation. Brian