Soft washing
| Soft washing | |
| Type | Roof cleaning method |
|---|---|
| Pressure | Low |
| Agent | Biocidal solution |
| Result | Appears over weeks, not on the day |
| Defined by | Trade practice; no statute or standard |
Soft washing is the application of a biocidal solution to a roof at low pressure, leaving the growth to die back and weather off over the following weeks and months rather than removing it mechanically on the day. No statute or published standard defines the method, so the description here is of established trade practice and carries no citation for the technique itself. What is regulated is the surrounding activity: the work is work at height,[1] and any biocidal product applied must be authorised for that use.[2]
How it works[edit]
The solution is applied at a pressure high enough to distribute it and no higher, so the covering is wetted rather than struck. The chemical then needs contact time: it kills the growth, and weather removes what is dead over a period that is measured in weeks for algae and can run to a season or more for established moss and lichen.
The immediate visual result is therefore small, which is the method's principal commercial difficulty and the source of most disputes about it. A roof soft washed on Monday looks much as it did on Sunday.
Why it suits fragile coverings[edit]
Because nothing abrades the surface, the method does not remove the fired finish of a clay tile[3] or the applied surface of a concrete tile,[4] and it does not disturb slates held by tired nails. On coverings where the surface is not renewable, that is the whole argument for it.
It also keeps the operative off the roof more often than mechanical methods do, which sits higher in the hierarchy the Work at Height Regulations set out.[1]
Regulatory position[edit]
Soft washing is biocide application, so the product used must be authorised for the use and applied on the conditions of its authorisation.[2] The exposure of the person applying it is separately governed by the Control of Substances Hazardous to Health Regulations 2002.[5] Run-off reaches gutters and then the ground or the drainage system, and where an authorisation restricts that, the restriction is a term of lawful use.[2]
See also
- Biocides in roof cleaning
- Pressure washing a roof
- Roof cleaning
- Biological growth on roofs
- Biocidal Products Regulation
References
- abThe Work at Height Regulations 2005. legislation.gov.uk. Retrieved 2026-09-05
- abcRegulation (EU) No 528/2012 concerning the making available on the market and use of biocidal products. legislation.gov.uk. Retrieved 2026-09-05
- ^BS EN 1304:2013: Clay roofing tiles and fittings. Product definitions and specifications. BSI. Retrieved 2026-09-05
- ^BS EN 490: Concrete roofing tiles and fittings. Product specifications. BSI. Retrieved 2026-09-05
- ^The Control of Substances Hazardous to Health Regulations 2002. legislation.gov.uk. Retrieved 2026-09-05