North-Facing Patio Cleaning: Heavy Black Spot Removal

Start with the thing nobody in this trade says out loud: the photographs are wet. Every before-and-after you have ever scrolled past, including the ones further up this page, was taken while the surface was still soaked — because wet stone is saturated stone, the colour goes deep, the contrast doubles, and the result looks perhaps a third better than it will look on Tuesday. This patio dried and went quieter. It was still an excellent result. It was not the photograph.

We photograph wet because that is when we are standing there with the kit in the van and the light still good, and because it is genuinely the moment the work looks like what it felt like. But if a contractor shows you only soaked surfaces and never says why, they are letting an optical effect do some of the selling. So: expect your patio to look like the wet picture for about an hour, and like a good version of itself after that. Anyone promising otherwise is selling a sealant and has not mentioned it yet.

As for why this patio and not the other one — it was the north side, and that is almost the entire explanation. The front of the same house, the same slabs, laid at the same time by the same people, took a few minutes. This side sits between a wall and a fence facing away from the sun, so after rain it stays wet for hours longer than the front does. Colonisation is not a function of neglect or of how much traffic a surface gets. It is a function of how long the surface stays damp, and aspect decides that.

The black spot here was not a sheet, it was a population — discrete colonies scattered dense across the whole area, some the size of a five-pence piece, some merged into patches. That changes the work completely. A uniform film you can treat in passes. Colonies have to be met individually, worked, and in places revisited, because the treatment only does anything where it actually lands and stays. Which is why this took the afternoon rather than the hour somebody estimating it from a photograph would have allowed.

This is the honest reason surfaces like this are hard to quote. With window cleaning you can be genuinely accurate — a given house, a given number of panes, and experience closes the gap to a few minutes either way. A colonised patio has two variables that do not behave: the area, which you can measure, and the density and maturity of what is growing on it, which you cannot, not reliably, not from the pavement and sometimes not until the first section is done.

Which leads somewhere uncomfortable about how this industry is organised. Take an eight-hour day and put fifteen jobs on it and you have thirty-two minutes per job including the drive between them. Put twenty on and you have twenty-four. I have seen worksheets like that. Nobody on one of those sheets is dwelling a treatment for an hour or working a lichen colony twice, not because they are bad at the work but because the arithmetic has already decided what they are allowed to do. Splash and dash is not a character flaw. It is a schedule.

There is one more variable and it is the one nobody puts in writing: the tradesman. I am not twenty any more, and I have physical health conditions, so the pace I work at is a chosen one rather than a maximum one. That is not an apology. Work done at a sustainable pace on a surface like this is better work — steadier passes, more attention paid to the patches that need it, fewer decisions made because the light is going. A trade that treats speed as the only measure of competence ends up with neither.

This one did not begin well, either. I was late, because one job had run into the next, which is the commonest reason any tradesman is late and the least often believed. What I got on the phone, and again on arrival, was rudeness of a sort I do not accept any more. So I said so, calmly, and offered the choice: the conversation changes or I go. It changed. Her husband, meanwhile, apologised, moved everything off the patio himself, and could not have been more decent about any of it.

When it was done he came out and said “wow”. Then apologised again, then said it a second time. That is the entire review and I have never needed a better one. It is also why the job got finished, because a household is not one person and none of it was his fault. Setting a boundary at the start is what made the rest of the afternoon possible — and the afternoon is what the photographs are of.