When to Rinse After Softwashing

Mark Cave

I see guys all the time you know, they've just finished a brilliant roof clean, got all the moss scraped off, sprayed their sodium hypochlorite mix, and then-- and then they spend another hour dragging a heavy pressure hose up a ladder just to rinse the whole bloody thing down. And I'm standing there thinking, what on earth are you doing? You are quite literally, um, you're fighting the chemistry. You're wasting your own time, your water, and your profit margin. On a standard pitched roof, once you've sprayed that second coat of sodium hypochlorite, you- you just don't need to rinse it. The chemical, see, it's an oxidizer. It has this active window of about half an hour, maybe forty-five minutes, where it's doing the hard graft of killing off the organic spores, the lichen, the black mold. But once that reaction is done, and especially once the sun hits it, that hypochlorite breaks down rapidly. It degrades into simple salt and water. It gasses off. It becomes completely inert. So, what are you actually rinsing off? A bit of salt residue that Mother Nature is going to wash away with the next light drizzle anyway. It's- it's completely pointless. Now, I know some of you are thinking, "But Mark, what about driveways? What about patios?" And, yeah, that is where we have to look at the exceptions. Because if you've got a flat surface, say a block-paved driveway or an Indian sandstone patio, and you've got kids running around, or- or there's a cat flap with pets coming in and out... well, you can't just leave active chemical sitting there to dry. A dog walks across a dry, unrinsed patio, licks its paws... that's a call to the vet you don't want to be responsible for. In those specific scenarios, my absolute favorite phrase applies: dilution is the solution to pollution. If you've got pets, if you've got toddlers, as soon as that chemical has done its job and cleared the black spots, you grab the garden hose and you flush the entire area. You dilute that mix down to a fraction of a percent until it is totally safe and inert. But if it's a closed-off commercial yard? Or a roof thirty feet in the air? Save your water. Let the chemistry do the work, pack up your van, and crack on to the next job.

Mark Cave

But-- and this is a massive "but" --there are some surfaces where if you walk away without a thorough, meticulous rinse, you are going to absolutely ruin the job and potentially face a massive claim. Let's talk about coloured render first. Silicon-based renders, like K Rend or Monocouche... they are incredibly porous. If you spray sodium hypochlorite on render to clear the algae, and you decide to just leave it to dry... oh, boy. What happens is the water evaporates, but it leaves behind a heavy deposit of salt deep inside the pores of the render. Now, salt is hydrophilic. It loves water. It literally draws moisture out of the air and traps it inside the wall. And what does green and red algae need to thrive? Moisture. By leaving that salt residue on the render, you are actually creating the perfect, damp breeding ground. You will find that within a few months, the algae returns twice as fast and twice as thick as before. Always, always rinse render. Flush that salt out of the pores. And then there's wood. Wooden decking is the ultimate trap for a greenhorn contractor. Wood is naturally thirsty. If you spray a strong sodium hypochlorite mix onto a bone-dry deck, the wood fibers will drink that bleach deep down into the grain. And once it's in there, you cannot get it out. It carries on bleaching, turns the wood this horrible, ghostly, silvery white, like driftwood that's been lost in the Atlantic for ten years. Worse, it actually damages the cellular structure of the wood, causing it to peel and flake. It's- it's like a severe case of sunburn on human skin. To prevent that "sunburn" damage, you have to follow a very specific workflow. First, you pre-wet the wood. You give the deck a thorough drink of clean water first, so those fibers plump up. Now the wood is full, it's not thirsty. Then you apply a light, gentle softwash mix-- say 1% or maybe 1.5% strength, with a good surfactant like Clever Wash to make it stick. And then, the critical bit: you must rinse it thoroughly within fifteen to twenty minutes. Do not let it sit, do not let it dry out. Flush it clean, dilute the residue, and let it dry naturally. When you return the next day, you'll be absolutely chuffed. It'll look like brand-new, golden, Tanalised timber. Get your on-site workflows right, understand which surfaces need the water and which ones don't, and you'll protect your client's property, preserve the building's integrity, and build a reputation as a proper professional. Alright, that's enough waffling from me today. Go put it into practice, stay safe, and I'll catch you on the next chat. Bye-bye for now.