How to choose a soft washing company: questions to ask and red flags

Updated 6 November 2026 · By the Soft Wash team

Short answer: Choose a soft washing company that can tell you exactly which product it uses on your surface and why, explain how plants, windows and drains will be protected, describe how it will reach high areas safely, and give a clear written price. Be wary of anyone who plans to use high pressure on render or roofs, will not say what chemicals they use, or promises results that sound too good to be true.

How to choose a soft washing company: questions to ask and red flags

Why it matters

Soft washing is simple to describe but easy to get wrong. The wrong solution strength can mark render, bleach timber, damage plants or leave streaks. Too much pressure defeats the point of the method. Poor rinsing leaves residue on glass and paintwork, and careless run-off can kill plants or pollute a stream. The difference between a good and a bad result is mostly down to the knowledge of the person doing it.

Questions to ask

Question	What a good answer sounds like
What product will you use on my surface?	A named product or active ingredient, matched to your render, roof or masonry
What pressure will you clean at?	Low pressure for application and rinsing, not a pressure washer on render or roof tiles
How will my plants and lawn be protected?	Pre-wetting, covering where needed, controlled application and rinsing afterwards
Where will the run-off go?	Diluted and kept out of surface water drains, ponds and watercourses
How will you reach the high areas?	Poles, ladders, towers or powered access, with a plan for working safely at height
Will all the staining go on the day?	An honest answer that lichen and some marks fade over weeks
Can I see the safety data sheet?	Yes, without hesitation

Chemicals and the law

Most soft wash solutions are based on sodium hypochlorite or quaternary ammonium compounds. Products sold to kill algae, moss and mould are biocides, and in Great Britain biocidal products are regulated by the Health and Safety Executive. Contractors also have duties under COSHH to assess and control the risks from the chemicals they use.

You do not need to be an expert in this, but a competent contractor should be comfortable telling you what they are using, showing you the safety data sheet and explaining what precautions they take. Vague answers such as a secret mix or just bleach, with no explanation of strength or safety, are a warning sign.

Red flags

Planning to pressure wash render, painted walls or roof tiles
Refusing to say what product will be used
No mention of plant protection or rinsing
Letting run-off go straight into roadside or yard drains
Walking all over a fragile roof rather than using safe access
Promising all staining, including rust and paint, will disappear
Cold calling and pressure to book on the spot
A price far below every other quote with no explanation

Comparing quotes

Make sure each quote covers the same surfaces and the same scope. One company may include gutter clearing, window rinsing and outbuildings, while another quotes only for the main walls. Ask whether access equipment is included, whether the price is fixed, and what happens if some staining remains after the agreed time.

Send every company the same photos of each elevation, the roof if relevant, and the type of surface. That makes it easier to compare like with like, and it helps spot a quote that has misjudged the job.

Questions about your particular property

Every property has its own quirks, so ask how the contractor will deal with yours. If you have silicone or monocouche render, ask whether they have cleaned that type before and whether they will check the render manufacturer's guidance. If the house is old, with soft brick, stone or lime mortar, ask how they will keep the treatment gentle. If there is a conservatory, a pond, a vegetable garden or a car port close to the walls, ask how each will be protected.

For roofs, ask how they will get onto and work on the roof safely, how much they expect to walk on the tiles, and whether gutters will be cleared afterwards. For taller buildings, ask what access equipment they will use and whether any permits are needed to place it on a pavement or road. A contractor who has clearly thought these things through is far more likely to do a careful job.

What a good job looks like

Plants soaked and protected before any solution is applied
Windows and doors kept shut during application
An even application with no streaks or tide marks
Glass, frames and paintwork rinsed clean afterwards
Plants and paving rinsed again at the end
A walk round with an honest explanation of what will keep fading
Gutters and paths left free of moss and debris

A good contractor will also point out problems they notice, such as cracked render, leaking gutters or slipped tiles, because these affect how long the clean will last.