Fungicidal Wash

A number of fungicidal wash products exist on the market that can help clear moss and other fungal growth from asbestos roofs.

Most are simply diluted bleaches that kill moss on contact, resulting in it detaching from the roof surface and falling into the gutters.

However, this process can take several months to take effect before the moss disappears.

Bearing in mind that all waste from an asbestos roof is considered to be contaminated, there is no effective method of collecting the waste and preventing it from entering the drainage system.

If all you wish to do is remove the fungal growth, then a wash might be the cheapest option, but bear in mind that the roof will not be clean enough for coating afterwards, so there is only limited benefit in using this method of cleaning.

Closed Box

It is dangerous to use pressure washers with ordinary nozzles on asbestos roofs, since the pressure can destroy the surface, contaminating the area beneath.

A safer and HSE Approved method is to use a closed box pressure washer.

This is similar to a patio cleaner attachment, but larger and more complex, often with wheels to allow it to be pulled up and down roof slopes with ease.

Because the jet of water is constantly spinning and the box is moving, it is less likely that it will damage the surface of the roof.

This method can result in water ingress and gutter overflow due to the amount of water being used.

All waste water must be filtered and slurry collected and disposed of as contaminated waste.


Wet Scrape

Most asbestos roofs are covered in moss, lichen and other types of fungal growth.

This adds to the weight of the roof and in extreme cases, can penetrate the asbestos cement, severely weakening the already fragile surface.

The first stage to cleaning should therefore be to wet down the roof and scrape off any weed or moss growth, which should be placed into designated asbestos waste bags.

The waste must be considered to be contaminated and therefore should be disposed of by a licensed disposal contractor and a consignment note issued and filed for the health and safety file.

A wet scrape can be carried out in isolation if all you need to do is remove heavy vegetation.


Steam cleaning is less commonly used than other methods, as it is not an HSE approved process.

This doesn’t mean that steam cleaning cannot be undertaken, rather that more care has to be taken to ensure that safe working practices are adhered to.

Steam cleaning machines are available that deliver up to 150°c steam to the lance. This kills moss and lichen on contact, resulting in a much deeper clean that using water alone.

The steam begins to evaporate as soon as it leaves the lance, resulting in far lower water run-off into the gutters, reducing the chance of water ingress and overflow.

Waste water needs to be filtered and residue disposed of as contaminated waste.

Asbestos Roof Cleaning Considerations

If your roof is leaking, it is likely to leak even more during the cleaning process

If you have damaged roof lights, it is good practice to replace these prior to cleaning

Expect water and slurry to overflow from the gutters during a closed box pressure wash

Pressure washers and steam cleaners are noisy when in use.

Cleaning an asbestos roof is a specialist job requiring specialist equipment

Keep your neighbours informed because they will be watching!

If you would like further information or assistance on this subject, please call one of our building surveyors on 0121 709 5352

Commercial Property Surveys Ltd

Unit 3 Radway Industrial Estate
Radway Road
West Midlands
B90 4NR

Tel: 0121 711 7110

Liquasil Ltd

Unit 8 Radway Industrial Estate
Radway Road
West Midlands
B90 4NR

Tel: 0121 709 5352

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