Softwashing Takes More Than Chemicals: 240 Things to Get Right

Mark Cave

Picture this. You're standing on a driveway, looking up at a concrete tile roof. It's streaked black and green. The customer says, "Can't you just blast it off? Surely that's quicker." In about ten seconds, you've got a decision to make. That one decision touches surface identification, chemistry, water getting under the tiles, your own safety, and the price you're about to quote. Ten seconds. That's what I want to unpack today.

Mark Cave

I'm Mark Cave, founder of SoftWash UK. We recently mapped out everything a properly trained contractor needs to understand, and the list came to 240 topics. Two hundred and forty. Not because we enjoy making things complicated, but because that's what the trade actually involves. If you caught the episode on why patios turn green again, you'll remember it wasn't about force. It was moisture, porosity and biology. Today I'm zooming right out.

Mark Cave

Let's start with that roof. Marley Roofing says the use of high powered jet washes is not recommended, because it can damage the surface of the tile and reduce its expected life. Wienerberger, who make Sandtoft tiles, warn that the spray can strip colour from concrete tiles. Forticrete say power washing removes fines in the concrete and would invalidate their guarantee. So the quick option can cost the customer their warranty. The approach those manufacturers point towards is manual scraping of the bulk moss, then a low pressure biocidal treatment. It's slower. It's harder work. But it leaves the roof intact.

Mark Cave

And here's something that catches people out. Sometimes a roof looks patchy or bleached after cleaning, and the contractor gets blamed. Often, the cleaning has simply revealed what was already there. Worn aggregate, lost surface fines, a coating that had gone years ago. The dirt was hiding it. If you didn't photograph the roof before you started, how do you prove that?

Mark Cave

Now move to the walls. Through colour monocouche render, and silicone render on external wall insulation, can be permanently damaged by pressure or by chemical that's too strong. Painted render can chalk, flake, or fail at the binder if there's an underlying defect nobody noticed. Then there's stone. Limestone and travertine are acid sensitive, so the wrong product can do real harm. Indian sandstone is porous, so how long you leave a chemical on it matters enormously. Same job description, "clean the surface", completely different decisions. That's why I keep saying knowledge comes before products.

Mark Cave

Which brings me to chemistry. Sodium hypochlorite works by rapid oxidation. It's brilliant on organic biofilm like algae and bacteria. But it gives no residual protection against spores landing on the surface afterwards. A quaternary ammonium biocide such as DDAC works differently. It's a slower clean, but it can suppress regrowth on roofs and masonry. Neither is better. They do different jobs.

Mark Cave

And here's the mistake I'd urge you to avoid. Sodium hypochlorite does nothing useful for rust, efflorescence, lead staining or oil. If you put bleach on a rust stain, you waste product and you risk etching the surface. Rust needs something like oxalic acid. Diagnose first, then choose the chemistry. Which also means never letting acids and hypochlorite near each other. Mixing them produces toxic chlorine gas. So segregation, labelling and a clear mixing procedure aren't paperwork. They're how you go home safe.

Mark Cave

Then there's dwell time and wetting, and this is where I see strength used as a crutch. A good bleach compatible surfactant, Clever Wash is the one we make, lowers surface tension so the mix clings to a vertical wall instead of running off into the flowerbed or towards a drain. If your product won't stay put, the answer is rarely a stronger mix. That just means more risk for plants, more runoff, and more wasted chemical. Fix the cling and the contact time first.

Mark Cave

Let's talk safety, because low pressure does not mean low risk. Holding a safety data sheet isn't a COSHH assessment. A proper assessment reflects the actual task, the actual site, how people could be exposed, and the ventilation. Same with drainage. Before you spray a drop, find out where the water goes. A surface water gully often leads towards a stream, not a treatment works. Pre wetting nearby plants helps protect them, but it isn't a substitute for containing runoff.

Mark Cave

And now the one that hits your wallet. Underquoting is very often a technical knowledge problem disguised as a pricing problem. If you quote on spray time or square metres alone, you've forgotten the survey, protecting surfaces, taping sockets, setting up access, controlled rinsing, and dealing with waste. You haven't priced the job. You've priced the fun part. Someone who understands the process knows what's involved, quotes for it, photographs existing defects, explains honestly that a slow biocide may take weeks or months to show its full result, and sometimes walks away from a failing surface. That discipline is what a splash and dash cleaner doesn't have.

Mark Cave

So what can you do this week? One, photograph every surface before you touch it. Two, identify before you choose. Ask yourself, is this organic or inorganic? Three, test patch somewhere discreet and watch what happens. Four, check where the water is heading. Five, write down what's included in your price, including the boring bits. None of that costs anything.

Mark Cave

Podcasts, articles and free guides are a great starting point, and our Softwashing Knowledge Centre at softwashing.uk has plenty. But a quick clip online can't replace structured learning across chemical selection, surface identification, equipment setup, safety and pricing. That's exactly why we built the CPD Certified Softwash Training Course. It's online, so you learn at your own pace, and it's built from years of real industry experience to help you avoid expensive mistakes. Completing it also gives you the opportunity to become an Approved Softwash Applicator, with a directory listing and a place in the National Association of Softwash community. The aim has always been to raise standards, and you can see the training and resources at softwashing.uk.

Mark Cave

Here's a challenge before the next episode. Pick one job you've done recently and ask honestly, which of those 240 topics did I guess at? Whatever you land on, that's your next thing to learn. Thanks for listening, and I'll catch you in the next one.