Should you scrape moss from a roof before soft washing?

When soft washing a roof, should you first scrape moss from the roof, or not? This is a question we are frequently asked. So we thought to clarify the practicalities and legalities of removing moss from roofs in light of our experience.

A spray-only treatment – with any softwash chemical – of roof moss is never completely satisfactory.

There is also an important regulatory consideration. The control of moss is regulated under the Plant Protection Products Regulations, and products making claims to control moss require the appropriate Plant Protection Product authorisation.

Click here to read the current HSE guidance on the control of moss.

You can also read our Trade Tip explaining the regulations and practicalities of controlling moss when soft washing.

Through numerous trial and error experiments over several years, manual scraping prior to treating the biofilm with Benz Bio Cleanze proved to be the most effective approach.

Spraying with Benz Lightning Cleanze

In the past we experimented with spraying moss with highly concentrated Lightning Cleanze.

This approach quickly turned the moss into a mush. The problem was that, if not removed from the roof, rain washed the mush into gutters, downpipes and drains. Obviously this could cause serious, hard to remove blockages.

Removing the mush by hand, prior to it entering the drainage system, proved to be messy, difficult, potentially dangerous and highly unpleasant.

This approach led to the possibility of active sodium hypochlorite remaining in the mush, so stringent H&S precautions, including appropriate PPE, had to be implemented.

Why we scrape moss before soft washing

Quick tip: HSE currently states that the control of moss is regulated under the GB and EU Plant Protection Products Regulations. Products making claims against moss therefore require the appropriate Plant Protection Product authorisation.

For this reason, and because we have found it to be the most practical and effective approach, we always remove the bulk moss by manual scraping before treating the remaining biofilm with Bio Cleanze.

Through many years of experience, we've found it to be most effective to remove moss from a roof prior to soft washing by using Benz Professional Roof Moss Scrapers.

Treating the roof after scraping

After the bulk moss has been removed, treat the remaining biofilm and biological growth with Benz Bio Cleanze.

For a scraped slate or tiled roof, Bio Cleanze is typically applied at approximately 25:1, following our current application guidance.

Click here to read our full roof softwashing use guidelines.

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

The Benz Team

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