Nairobi is kinder to buildings than the coast, but it is not gentle. The sun is strong at altitude, the long rains are heavy, and dust gets into everything for months at a time. Those three things decide which finishes are still worth looking at a decade later.

The useful test is what a material does when it stops being new. Coursed stone left unrendered weathers and gains depth. Painted render, on the same wall, cracks along every movement joint and shows a line of repair each time it is patched. Neither is wrong, but one of them is a maintenance commitment and the other is not, and that should be a decision rather than a discovery.

Roofs follow the same logic. A clay tile keeps its colour because the colour is the material. A coated steel sheet keeps its colour until the coating goes, and then all of it goes at once. Steel is lighter, cheaper to frame and perfectly sensible, particularly over light-gauge trusses. It just has a replacement date and tile mostly does not.

Inside, the same question. Timber floors, whether hardwood or a caramelised bamboo, can be sanded and re-oiled several times across a life. A lacquered finish cannot: when it goes it has to come off entirely. Large-format tile is close to permanent, which is a virtue in wet areas and a liability in a room whose use will change.

The arithmetic is unromantic. Materials that age well usually cost more at handover and less across the twenty years that follow. For someone building to sell in three years that is a bad trade. For someone building the house they intend to grow old in, it is the only trade that matters, and it is worth asking a client which of the two they actually are before specifying anything.