AsbestosRoofing.co.uk

With age, the surface of an asbestos roof is likely to be discoloured and, unless it’s been regularly maintained, also covered in moss, algae and lichen.

Although some people are of the opinion that this aged look adds character, lichen in partcular, can cause severe damage if it grows through to the underside of the roof, when asbestos contamination to the space below can occur.

This is a piece of moss taken from an asbestos cement roof

This is the underside of the moss - complete with the asbestos residue

We recommend that roofs affected by moss and lichen are cleaned off and sealed with a proprietary sealer.

As you can see from the two images above, the moss actually eats in to the roof fabric, which delaminates and breaks off.

If you do not use a competent contractor, the moss, along with asbestos and cement residue can find itself into the water course, which is against HSE guidelines and can result in heavy fines, or in severe cases, imprisonment.

There are several methods of cleaning an asbestos roof but in many cases, the cost of health and safety equipment (scaffolding, netting etc) can exceed the actual cost of doing the works!

Dry Scraping
Often carried out using a wire or stiff brush, this method should be avoided, as it can result in high fibre release.

If a roof is heavily contaminated with moss growth however, this should be scraped off or loosened prior to the roof being properly cleaned. This can be done using soft brushes as long as the surface is thoroughly wetted beforehand.

Any moss and other debris on the roof, should be collected and placed into approved asbestos waste bags for proper disposal, since the moss will undoubtedly contain asbestos fibres and must therefore be treated as contaminated waste and disposed of properly.

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 – subsequent clean-up 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.

This work is usually carried out by specialist contractors who have not only the correct equipment, but also the necessary filtration plant necessary to collect the slurry and prevent asbestos fibres from entering the drainage system of the building.

It is vitally important to conduct an initial feasibility study (roof survey) of the roof in question, as some areas of the roof might be weaker than others and these need to be marked out prior to commencement of cleaning, to ensure that the pressure of the water can be adjusted in those areas.

Some roofs are not suitable for cleaning using this method.

WARNING: Without taking these essential precautions, your asbestos roof could fail and contaminate a property and the surrounding area. Do not leave your choice of contractor to chance – tender the works to suitably qualified contractors with the correct levels of insurance.

Once properly and professionally cleaned, an asbestos cement roof should be re-sealed, with particular attention paid to roof lights and fixings which will often be rusty, with failed gromets.

Ideally, your chosen contractor should also reseal the roof and be able to offer an on-going maintenance programme – otherwise, you coluld find that you have difficulty with any guarantees, or of problems arise later.

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 and gentle soft-brushing.

Dead lichen crusts are more difficult to remove and should be left in place. Roots of dead mosses may hold loosened asbestos fibres. This waste must be properly collected and disposed of.

Live lichen and moss, when left in-situ prior to coating a roof, will continue to cause problems afterwards, though some contractors will try and tell you that by sealing them in underneath a waterproof membrane, that they will die off.

This is true, but unfortunately, as they die off, the detach from the roof and often take the new coating with them, leaving you unsealed and vulnerable areas.

Asbestos Roof Cleaning Costs

The cost of cleaning an asbestos roof is expensive, as it must be carried out by competent roofers using specialist materials and safety equipment.

Often, it’s the safety equipment that increases the cost – things like scaffolding, safety netting and cherry pickers need to be factored in.

For this reason, it’s often wise to consider cleaning an asbestos roof when you’re also looking at re-coating or overcladding, as the safety equipment will be required anyway.

The cost of cleaning a roof varies from company to company, but in our experience, at least £15-£20 per square metre should be allowed if it’s to be done properly with all of the correct health and safety equipment. This does not include re-coating and sealing the roof aftwerwards.

As independent and unbiased asbestos and building surveyors, we can prepare a full specification of works and tender the job on your behalf, following a comprehensive roof survey to determine the suitability of your roof for cleaning.

Our fees for running such a project are 10% of the contract value, but this will repay itself with the other savings that we can make on your behalf.

Roof surveys start from £750 plus VAT.

We regret that we are not able to assist domestic customers.

Please note that our PI insurance dictates that we cannot recommend individual companies without first having carried out a feasibility survey. 

To discuss or arrange a commercial property  asbestos roof survey anywhere in the UK,
please call David Carter on 0121 711 7110 Mon-Fri 8:30am – 6:00 pm) or complete the form below: