How to safely soft wash asbestos roof slates, tiles & sheeting

September 15, 2021

How to safely soft wash asbestos roof slates, tiles & sheeting

Many soft wash contractors can be unsure of the safest way to soft wash asbestos roofs. So in this post we lay out the best practices we've learned from our experience of running a soft washing business since 2013. 

The procedure for soft washing asbestos

Asbestos must, at all times, be treated with care and with serious attention given to health & safety procedures.

Keeping the surface damp (the first priority when starting work) is the simplest and most important way of minimising the possibility of fibres entering your lungs.

Repeat water spraying frequently during the scraping process to ensure the asbestos does not dry out. The water will lay the fibres, preventing them from lifting into the air where they can be taken into your lungs. 

Quick tip: Never dry-scrape asbestos unless you are wearing an asbestos breathing mask or other suitable respiratory protection that is certified as suitable for filtering asbestos fibres. Click here to explore asbestos PPE

How to clean asbestos roofing

After carefully hosing off the worst of the loose organic material and collecting it safely, treat an asbestos roof with Benz Lightning Cleanze biocide diluted 5:1.

Follow this by applying Benz Tornado Cleanze as a spot-cleaner on the worst affected areas.

If there's a lot of black lichen, and leave it for a good 60 minutes to activate.

If black lichen has been allowed to grow into an asbestos roof, it will probably need gentle scraping after the first treatment with Lightning Cleanze biocide.

To do the best possible job, post-treat asbestos roofs with Benz Bio Cleanze, which will reduce re-colonisation and extend the time that the roof stays clean and free from re-contamination.

UK HSE Asbestos Cleaning Guidelines

How dangerous is it to soft wash asbestos?

Although the danger when working with asbestos in the open air is relatively small compared to working with asbestos in a confined space, the safest route is of course to wear suitable, asbestos fibre approved, breathing apparatus.

The asbestos can then be treated with Bio Cleanze and/or Lightning Cleanze. Which to use depends on the type of roof and the expectations of your customer.

Mostly we treat roofs with Bio Cleanze only but on the illustrated garage roof Lightning Cleanze turned out to be the most effective treatment, not least because the customer wanted a rapid result.

The photo at the top of this post shows the completed asbestos sheeted garage roof that we treated with Lightning Cleanze. The photo below shows three preliminary stages of the work in progress, so you can see what we were faced with and how the job progressed.

How to safely soft wash asbestos roof slates, tiles & asbestos sheeting



Soft washing asbestos roof slates and tiles

It's always good working practice to check the material of the slates you intend treating because some older man-made artificial slates (often called "composite" slates) include asbestos.The asbestos is included in the fibre cement the slates are made from.

Newer man-made slates are usually made without asbestos but anything pre 1970 should be checked. A sample can be sent away to a lab to be tested.

We check every roof for asbestos before scraping it, even though the danger is very slight given the open-air conditions, and that the slates are wet all the time when we are scraping them.

Which insurance companies cover the risk of soft washing asbestos?

Modern artificial slates such as Tegral are not made from asbestos-containing material and so are easy and safe to treat.

It's best not to work with old asbestos slates if feel unsure of what you are doing and/or you cannot get insurance.

The best insurance company for soft washing that we know of at the moment is Hiscox. Contact info below:




We hope this information is helpful and sincerely wish you great success in your soft washing business,

Ben, Leo, Fiona, Stevie & Anthony

Click here to get more practical soft washing how-to tips

How to find answers to most soft washing questions: Simply enter a relevant "keyword" or short phrase – e.g. keyword for the above link = "how-to" – into our in-site Search Engine (magnifying glass icon on the main menu).

Order Benz Softwash chemicals & equipment online or by phone:

GB (England, Scotland, Wales)

Phone: 0800 70 74 222 


Ireland and other countries

Phone: 00353 214 622 978


Lines open Monday - Friday, 9am – 5pm

Please note: The above numbers are for orders only (click here for tech support)

PS: Click here to set up your "Clean & Maintain" programme
. After completing an initial soft wash treatment, put your customer on a "Clean & Maintain" ongoing maintenance programme. Your customers will enjoy a permanently clean property and you will enjoy a steady stream of repeat business.

This is clearly a win-win arrangement for you and your customers.


Click here to explore the extensive range of Benz softwash cleaning chemicals & equipment

Benz Softwash Bio Cleanze DDAC biocide & Benz Softwash Lightning Cleanze SH sodium hypochlorite biocide

Leave a comment

Comments will be approved before showing up. Please revisit to read our response.

Also in Benz Trade Tips

Biological colonisation that soft washing controls
Biological colonisation that soft washing controls

May 24, 2024

Do you know the types of biological growth that give rise to the "dirty" appearance of properties, and customers want removed by soft washing?

Click the link on this page to find out ...

View full article →

Why does Benz Bio Cleanze contain IPA? (video)
Why does Benz Bio Cleanze contain IPA? (video)

May 17, 2024 2 Comments

Why do we add IPA (Isopropyl Alcohol) to Benz Bio Cleanze?

Click the link on this page to find out ...

View full article →

Resin bound bonded driveway
How to soft wash resin bonded/bound driveways

May 10, 2024

Many resin bound or bonded driveways come with guarantees and as such it's important not to invalidate them using chemicals that would degrade them.

Click the link on this page to learn the most effective methods for treating resin bound/bonded driveways ...

View full article →