How to soft wash thatched roofs

Thatched roofs require a different approach to most exterior cleaning projects. While algae, moss and fungal growth can shorten the lifespan of a thatched roof and spoil its appearance, using the wrong cleaning method can cause more harm than good.

If you plan to clean a thatched roof, focus on treating the biological growth while preserving the reeds. In most cases, that means using a quaternary ammonium biocide such as Bio Cleanze rather than a sodium hypochlorite-based treatment.

Treating a thatched roof with Bio Cleanze

Bio Cleanze works particularly well on thatched roofs because it penetrates deeply into the thatch and targets the algae, moss and fungi growing within it.

Apply two thorough treatments at a dilution suitable for the level of contamination. Heavily infested roofs often benefit from a stronger mix, while lighter growth can be treated at higher dilution rates. The goal is to fully saturate the affected areas and allow the product to reach as deeply into the thatch as possible.

The biological growth will normally die within a few days. Rain, sunlight and natural weathering then continue the cleaning process over the following months, gradually improving the appearance of the roof without the need for aggressive cleaning methods.

This approach cleans the roof while helping to preserve the integrity of the thatch.

Why we do not recommend Lightning Cleanze on thatch

Lightning Cleanze delivers near-instant cleaning on many exterior surfaces, but thatched roofs are different.

The priority when cleaning thatch is to preserve the reeds while controlling biological growth. For that reason, we do not recommend treating thatched roofs with Lightning Cleanze, Tornado Cleanze or other sodium hypochlorite-based products.

Bio Cleanze provides a safer and more suitable treatment for this type of surface and allows contractors to clean the roof without exposing the thatch to unnecessarily aggressive chemicals.

Does the thatch need treatment or replacement?

Cleaning and treatment can remove biological growth, but they cannot repair worn or deteriorated thatch.

If you are unsure whether a roof requires treatment or replacement, speak to an experienced local thatcher before carrying out any work. A qualified thatcher can assess the condition of the roof and determine whether cleaning is appropriate.

Many contractors build strong relationships with local thatchers and regularly refer work to one another. This helps ensure the customer receives the correct advice while creating additional opportunities for both businesses.

Is the IPA in Bio Cleanze a fire hazard?

No.

Bio Cleanze contains isopropyl alcohol (IPA) as part of the formulation that allows the product to hold its high concentration of active ingredient. Once diluted to normal working strengths, the amount of IPA applied to the roof is extremely small.

Any IPA present evaporates rapidly after application and does not create a practical fire risk when Bio Cleanze is used at the recommended dilution rates.

Listed buildings and permissions

Many thatched properties are listed buildings or are located within protected areas.

Before carrying out any treatment, check whether permissions or approvals are required. Property owners will often already know which local authority or conservation officer is responsible for the building.

Obtaining written confirmation before work begins helps protect both the contractor and the customer.

Ongoing maintenance

Regular maintenance helps prevent heavy recolonisation and reduces the need for more extensive treatments in the future.

Inspect the roof periodically and retreat when early signs of biological growth begin to appear. A proactive maintenance programme helps keep the roof cleaner for longer while reducing long-term costs for the property owner.

For contractors, maintenance treatments also create valuable repeat business and long-term customer relationships.

We hope that was helpful and wish you all the best in your soft washing business,

Team Benz