Cleaning and Maintenance
of Asbestos Roofing

After several years of use, the external surface of an asbestos roof becomes discoloured and is often found to be covered in lichens, algae and moss.

Although some people feel that this adds to aesthetic value of the roof, giving it a weathered look, it's sometimes necessary to clean the roof, for example, when wanting to apply a new surface coating.

There are several methods commonly employed for cleaning asbestos roofing:

	Dry Scraping. Often carried with a wire brush, this method should be avoided, as it can result in high exposures of fibre release.
	High Pressure Water Jetting. This used to be a common method for cleaning asbestos roofs but it has several problems including: - breaking down the cement matrix, causing fibre release; - asbestos fibres cannot absorb water - it creates a large amount of virtually unmanageable slurry, containing unbound asbestos fibres, leading to contamination of surrounding areas - subsequent cleanup can be very expensive!
	Remote Cleaning. There are remote controlled cleaning units available with enclosed rotary cleaning heads that use high pressure jets and brushes to clean asbestos cement roofing sheets. The operator is remote from the cleaning area, but provision still needs to be made to collect the resultant slurry.
	Surface Biocides. There is a wide range of approved pesticides available to kill plant material growing on asbestos cement surfaces and these will generally cause no damage to asbestos cement if used in the recommended concentrations in non-frosty conditions. They should be applied as a low pressure spray or a wash. Once the moss and algae is dead, they can be safely removed with water using gentle brushing. Dead lichen crusts are more difficult to remove and should be left in place. Roots of dead mosses may hold loosened asbestos fibres.

Working With Asbestos Cement Roofs

Maintenance covers a wide variety of activities such as the installation of replacement panels (if spares are available), the repair of panels and of course smaller works such as making attachments, fixtures or fittings to the sheets.

When conducting any maintenance to an asbestos cement roof (or any asbestos cement product, such as a downpipes, gutters etc.), there are a number of general precautions that must be taken to prevent or at least control exposure to asbestos fibres.

These include (but is not be limited to):

	Using non-asbestos materials
	Avoiding the need to attach items to asbestos cement products, or routing wiring or pipes through it
	Ensuring that surfaces prone to getting covered in dust and debris from the maintenance are covered in polythene sheeting
	Keeping the asbestos cement material wet when working on it
	Avoid breaking asbestos cement
	Using hand tools in preference to abrasive power or pneumatic tools. (Where power tools have to be used, they should be set at the lowest effective speed with additional precautions such as local exhaust ventilation. The area should also be shadow vacuumed with a suitable Type H vacuum cleaner)
	Wearing suitable protective clothing and respirators
	Keeping the area clean and tidy
	Avoiding cleaning methods such as dry sweeping and brushing
	Ensuring that the work area is thoroughly clean on completion of the work

Dismantling & Removing Asbestos Cement Sheeting
(These methods do not apply to any other form of asbestos)

Dismantling and removing asbestos cement sheets presents special problems, especially if they are old and crumbling.

On roofing, in addition to the risks associated by working at heights, asbestos sheeting is quite fragile and may not stand the weight of a person - even when new.

If demolishing a building or simply replacing an asbestos roof, the roof panels should, wherever possible be removed first, with extra care being taken not to break the panels.

The roof panels should be kept wet at all times during the dismantling and wherever possible, the sheets should be carefully lowered onto a clean hard surface.

Waste and debris should be kept damp and removed from the site as soon as possible to prevent it being crushed underfoot or by moving vehicles.

Broken asbestos sheets should never be bulldozed into piles.

Asbestos debris and waste should never be dry-swept.

The asbestos waste must be disposed of properly and safely. Wrapping in polythene is recommended, prior to loading into skips.