The building that aged well

Two buildings on the same street were completed in the same year. One looks cared for and one looks neglected, and the maintenance budgets have been almost identical.

The difference is in how each was designed to weather. Rain does not fall evenly on a façade; it runs, and where it runs it carries dirt and deposits it at the point where the flow stops. A projecting sill throws water clear of the wall below, so the dirt lands on the ground. A flush detail lets the water run down the surface, and within five years the wall carries a pattern of streaks that reads as neglect however often it is cleaned, because the streaks are in the material rather than on it.

Architects call this designing for patina, and it is one of the few areas where traditional detailing is straightforwardly better rather than merely different. Drips, overhangs, string courses and deep window reveals exist because somebody watched water move. Many twentieth-century buildings removed them for a flat appearance that photographs well on the day of completion and ages badly, and the photograph is what gets published.

The second factor is which materials improve with exposure. Copper, oak, lime render and some brick change colour and are read as maturing. Painted steel, untreated concrete and most sealants change colour and are read as failing. The distinction is cultural rather than technical and it is stable enough to design around.

The practical question at the design stage is therefore not how a building will look but how it will look in fifteen years when the surface has been written on by the weather. Everything outdoors is being written on, and the only choice is whether the writing was anticipated.