The questions to ask before you let anyone soft wash your render
Render is the most expensive surface on your house to get wrong. A pressure washer in the wrong hands, or the wrong chemical at the wrong strength, doesn't just leave a poor finish — it can mark the wall permanently and bring the staining back faster than before.
Knowing how to choose a render cleaner comes down to one thing: what you ask before they start. Most people don't know what to ask — so here are the six questions I'd put to anyone, me included, before letting them near a rendered wall. A good cleaner will welcome every one of them.
Will you ever use a pressure washer on my render?
The answer you want is a flat no. High-pressure water is the single most common cause of render damage — it drives moisture behind the surface, opens up hairline cracks, and on through-coloured renders like monocouche it strips the colour coat and leaves patchy, lightened scars that can't be undone. Render should be cleaned with a low-pressure soft wash that lifts the staining chemically. If someone reaches for a pressure washer "turned down low", that's still a risk you're carrying, not them.
Is the biocide you use an authorised product — and will you show me the label dilution?
This is the question almost nobody asks, and it's the one that separates a professional from a chancer. Killing the algae and lichen on your wall means controlling living organisms — which means the treatment has to be a properly authorised biocidal product, used at the dilution stated on its label. Decanting generic or pool-grade bleach, adding a bit of surfactant and a scent, isn't a clever shortcut — it isn't authorised for the job. A cleaner who knows their trade will tell you exactly what they use and be happy to show you the label.
Will you identify my render type before you touch the wall?
K-Rend, monocouche, silicone systems like Weber, Parex and Wetherby, older painted render — they stain differently and they need handling differently. A method that's right for one can dull or damage another. Anyone who quotes "render cleaning" as a single flat service, without first asking what's actually on your walls, is guessing. The right approach starts by identifying the system and testing the surface before anything is applied.
How will you protect my planting, pets and drains?
Even the correct product, used correctly, needs care around your garden. The honest answer isn't "don't worry, it's totally safe" — it's a method: pre-wetting surrounding plants before starting, working at the right dilution, and rinsing down responsibly so nothing pools or runs into a drain or watercourse. Be wary of anyone who waves the question away. Managing the run-off properly is part of the job, not an afterthought.
Who actually turns up on the day — you, or a crew I've never spoken to?
There's nothing wrong with a team, but you should know before they arrive. Ask who'll be on site, whether they'll knock before starting, and how they'll handle access and gates if you have pets. A surprising amount of grief comes down to a property being entered unannounced. The person who quotes the job and the person who does it being one and the same removes most of that risk at a stroke.
Will I see before-and-after photos of my own walls?
Not stock images of someone else's house — yours. A cleaner who documents every job, before and after, is telling you they stand behind the result and have nothing to hide. It also leaves you with an honest record of exactly what changed, which matters if you ever want to show the work was done properly.
A good answer to all six isn't a lot to ask. It's the difference between a wall that's clean and protected, and one that's been gambled with.
From Stephen
I'm Stephen Fudge — I clean every render myself, I'll tell you exactly what I'm putting on your walls and why, and you'll get the before-and-after photos to prove it. Twenty-five years on the tools, and a former career as a Local Authority Cleaning Inspector before that.
Get a straight answer on your render
Send us a couple of photos of your render and we will tell you the staining type, flag any problems, and give you an honest fixed price — usually within 24 hours. Prefer to talk? Call Stephen on 01283 293283.