Inland, heat arrives as glare. You shade a window and the room becomes usable. On the south coast, heat arrives as humidity, and shading a window does almost nothing. The room has to breathe or it is unusable by midday, whatever you do to the glass.

That single difference reorganises a building. Openings stop being about view and start being about cross-ventilation, which means they come in pairs and runs rather than one to a wall. Walls get thicker so they hold the day’s heat instead of passing it straight through. The roofline softens because a hard parapet edge, on a coast where the light is that strong, reads as a cut rather than a building.

Salt is the other half of it. It gets into reinforcement, and once it is there the problem is structural rather than cosmetic. Cover to steel matters more, mixes matter more, and the fixings that would be fine in Kikuyu will bleed rust down a wall in Diani within a season.

None of this is new. The Swahili building tradition solved it a long time ago, and the answers are still the right ones: lime-white render over thick walls, tall arched openings set to catch the breeze, coral rag stone where the building gets touched, and a perforated screen wall that ventilates, shades and decorates at the same time.

The screen is the piece worth dwelling on, because it is the one that looks decorative and is not. A jali wall moves air through a stair, keeps the sun off the treads, and throws a shifting field of light across the plaster opposite as the day goes round. Three jobs, one gesture, no moving parts and nothing to maintain. That is a better piece of engineering than most of what we bolt onto buildings now.

Getting a full-height perforated wall to run true, though, is a bricklaying problem before it is anything else.