Coating asbestos roofs is a recognised method of solving leaks and extending the life of the roof sheets.
The key thing to bear in mind is that condition is everything. If the roof sheets are delaminating (literally breaking apart) in large areas, then unfortunately, the roof is beyond coating and you will need to look at overcladding the asbestos roof, or replacing the asbestos roof sheets.
However, if the roof sheets are in decent condition, then coating might be a good option.
The process of coating an asbestos roof can usually be carried out even when the building beneath is occupied.
There are three stages:
- Cleaning the roof
- Preparing the roof
- Coating the roof
Looking at these in turm, cleaning the roof is typcially carried out in one, or a combination of the followsing ways;
Wet Scrape – this involves dampening the roof with water and then scraping off excessive moss and weed growth with mechanical scrapers or trowels. The reusltant debris should then be double-bagged in designated asbestos waster bags.
In some (rare) cases, this might be all the maintenance that is required. If the roof isn’t leaking, it might be best left alone!
Closed Box Pressure Washing – a closed box pressure washer is rather like a patio cleaner attachment on a jet wash machine, except that for large industrial roofs, a larger machine and cleaning head is required.
Steam Cleaning – This is a relatively recent development and involves using a powerful machine that superheats the water and creates a jet of steam that cleans the roof sheets using a steam lance. It is slower than a closed box pressure wash and is not approved for use by the HSE.
However, steam results in a cleaner substrate and it is ideal for use on fragile substrates. The water run-off from the cleaning process is vastly reduced and much easier to manage.
All waste from cleaning must be disposed of as asbestos contaminated waste and, waste water must be filtered to prevent asbestos from entering the drainage system.
The next stage is “surface preparation,” where any small repairs are taken care of and metal fixings are treated to prevent rust-breakthrough. The fixings are then sealed with a suitable sealant.
The final stage is to coat the roof with a suitable coating system throughout.
Asbestoseal from Liquasil Ltd is a purpose-made protective coating.
Coating can be an economical way of extending the life of an asbestos roof but this is entireley dependent upon the overall condition of the roof.
An independent asbestos roof survey is essential, because many such roofs have now reached or exceeded their economic life expectancy.
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