Porous cement/asbestos sheet roofing

[David Hearn]

As the rainy season approaches, I'd like to try and stop our garage getting wet. It appears that there's a leak of some sort (there's always a wet patch after heavy rain) and looking this morning after last night's rain it seems that the cement/asbestos sheeting for the roof is actually damp underneath - I guess it must be porous.

Is it meant to be porous? Its been there many years by the looks of it (though we've only been here 4 months). Is there anything I can paint on it (bearing in mind its not exactly a clean roof!) to stop it passing water through it?

The amount of water though that has come through (small long puddle under one of the metal supports) makes me wonder if its actually being blown under the capping, running down the underside of the sheets and then dropping off the metal supports where it touches the sheets.

Any suggestions? Its annoying having everything getting wet when it rains (well, boxes end up sitting in water, acting like sponges and then get smelly - I've lifted some up off the ground - but its a pain to have to do lots of them).

Thanks

D

[robgraham]

No, it's not meant to be porous, but it gets like this after a time. I've tried painting mine with the bitumastic adhesive that you stick roofing felt on with, diluted with a bit of paraffin or paint thinners. Works sometimes.

Rob Graham

[NJF]

No, it's not meant to be porous, but it gets like this after a time. I've tried painting mine with the bitumastic adhesive that you stick roofing felt on with, diluted with a bit of paraffin or paint thinners. Works sometimes.

Some car underseals work quite well, but you need to protect the surface from the sun afterwards, a good bathroom emulsion or eggshell paint on the underside will help as well, but plan on re-roofing it, perhaps retaining the original roof and putting a layer of insulation between. The cost of proper safe removal if it is an asbestos roof is frightening, so sealing and stabilising is the way I'm going, with a new covering layer over....

Niel.

[David Hearn]

I've looked into the disposing of the old sheeting, and our council tip ("Waste Transfer Station"!) takes them (I think up to 6 sheets at a time) free as long as they're double bagged and marked up as asbestos. They recommend soaking them (so you don't get lots of dust) and not breaking them up - but they're happy to take them.

Cement based asbestos sheets are, apparently, very low risk - other kinds of asbestos is very different.

[NJF]

I've looked into the disposing of the old sheeting, and our council tip ("Waste Transfer Station"!) takes them (I think up to 6 sheets at a time) free as long as they're double bagged and marked up as asbestos. They recommend soaking them (so you don't get lots of dust) and not breaking them up - but they're happy to take them. Cement based asbestos sheets are, apparently, very low risk - other kinds of asbestos is very different.

Your lucky then, most places down here won't touch them, and proper PPE, bagging equipment etc would still be required when handling. Having some experience of working in an industry where asbestos was a real problem I would not say ANY form is low risk, bound by cement and wetted you still will get fragments of fibres and thats all it takes... The quote for getting out double garage re-roofed was 2-3k more if we had the roof professionally removed, and atleast then should anything go wrong the contractors are properly insured etc. diy isn't a realist option IMHO.

Niel.

[Martin Moore]

Had the same problem myself with porous asbestos cement garage roof . It was dripping with water every time it rained... I used 2 coats of Thompsons Roof Seal to paint the whole roof (can be applied to damp surface) and its never leaked since.

Martin

[David Hearn]

Excellent - sounds like what I might be after. Do you know if its the sort of thing you can roller on? The roof has quite a shallow pitch, and I'm unsure how I would reach the middle of it without actually putting weight on the roof.

Thanks

D

[David Hearn]

("Waste Transfer Station"!) takes them (I think up to 6 sheets at

They recommend soaking them (so you don't get lots of dust) and

of asbestos is very different.

bagging equipment etc would still be required when handling.

problem I would not say ANY form is low risk, bound by cement

the roof professionally removed, and atleast then should

realist option IMHO.

That is a little strange, as when I was originally looking, I found a number of County Councils who said on their website that they took it - though I guess that doesn't mean they all would.

"cement bonded asbestos (as in sheet and guttering) does not present any significant health risk provided it is handled correctly"

"It contains a small amount of asbestos encapsulated within cement, which, in good condition, does not normally present a health risk."

Friable asbestos (eg. loose insulation) is very dangerous - this is where you can disperse the fragments just by touching it. Non-friable or bonded asbestos is very low risk. To disperse anything you need to cut or break the sheet, and even then its not guaranteed that any asbestos will be dispersed. As such, cement bonded asbestos sheeting is very different from the type that the Government *requires* licensed contractors to remove.

Obviously, you can choose to get someone in to do it, and let them take the risk - it very much depends on your temperment, approach to risk, and even spare cash! Also, as you said it was a double garage, I assume there's quite a lot of it.

From what I've seen of my garage, the number of sheets, the fact I'm 5 minutes from the place to drop off the sheets - I personally feel I would be happy to dispose of it myself - however, I accept not everyone would be, and that's fine. :) Also, I wouldn't be able to find £2-£3k to spend on it even if we needed to. ;)

D

[Dransfield]

I've started painting mine with "Roof Seal" which I think was from Homebase. It looks like it will do the job nicely, but it says to do 2 coats. A single garage roof is much bigger than I expected - its takin blimmin ages to do 1 coat! And I still haven't decided how I'm going to do the middle bit - put scaffy planks on roof and climb on it, or screw paintbrush to a broom handle and stay on stepladder.

Dranz

[Michael McNeil]

You work from longish planks or a sheet of board. The plank must cross the purlins. If you coat it with sealant couldn't you unroll a sheet of polypropylene over it and that should stick to the sealant (forming a completely watertight cover until the birds or some-such peck through)?

They normally crack top to bottom. If you can get the same profile you can cut strips to fit over the leaks. It would have to be pretty old to be the dangerous type. And plenty of people would have pointed it out to the council long before it became your problem.

Sealant by itself will fail eventually as the sheets move a lot in the wind. The movement causes the sealant to creep and after a while.....

[Martin Moore]

I used a cheap 4" brush, one of those plastic handled things with the white bristles that you use for walpaper paste, wouldn't recommend using a roller. Don't be put of by what people tell you about cracking or birds pecking through it as it dries flexible. Mine has been done over a year now and no signs of damage.

You can buy it in Homebase it comes in Grey or Black in 4 litre tins.

Just make sure you put some boards across the garage roof to work off.

Martin.

[David Hearn]

I have just realised that one side of the garage is up against a neighbours garden, so I'd need to get into their garden to do that side of the pitched roof... grr - things are never quite as straight forward - though I'm sure it'll be okay once I try it.

Thanks for the help.

D

[Asher Hoskins]

bagging equipment etc would still be required when handling.

problem I would not say ANY form is low risk, bound by cement

Restrictions on the disposal of fibre-cement sheeting have rather a lot more to do with successful lobbying of the HSE by the asbestos removal industry than actual risk. I forget the full details (if anyone's interested I can find out, my dad edits a scientific journal dealing with this sort of thing[1]), but as far as I can remember the asbestos undergoes a chemical change when mixed with cement which renders the fibres considerably less toxic should they later be released from the cement matrix.

I currently have all the roofing sheets from my 10'x14' garage (now reroofed in felted OSB - a dramatic improvement) lurking in my garden waiting for me to find a tip that'll take them. The annoying thing is that they're not even asbestos-fibre cement but glass-fibre cement. The two types look identical (I had some samples analysed to find out what their composition was) and so the same disposal restrictions apply.

Asher, not a fan of fibre-cement roofing...

[1]

[Mr Fiendish]

Felted 18mm OSB3 def. the way to go - I've recently redone mine and on the belt, braces AND spare bit of baler-twine principle also put a cover of lightweight corrugated galv. iron over the top to protect the felt. Oh yes - and painted the upperside of the OSB with bitumous paint before putting the felt down.

Had to use this roof as an access to a higher roof last week - feels really stable even with a 20' ladder standing on a board across the iron.

Carefully weighed the board/felt/iron - very little heavier than the asbestos/cement panels it replaced.

Barley Twist (Please put out the cats to reply direct)

[Stephen Gower]

"NJF" has a soton.ac.uk address, so I assume he is Southampton based and Netley Recycling Centre on Grange Road would be "round here". They take concrete asbestos for disposal.

[David Hemmings]

I prefer OSB over shuttering ply, and it is several pounds/sheet cheaper - saying that there is an increased board price working its way from manufacturers at the moment.

And even though OSB3 is structurally guaranteed and has the EN numbers stamped on it and standard 'CDX' play isn't structurally guaranteed, try convincing most builders to use OSB .......