Here’s how it usually goes. A faint brown ring appears on a bedroom ceiling. You tell yourself it’s old, or it’s condensation, or it’ll dry out on its own. A few wet weeks later it’s bigger, darker, and there’s a smell. By the time water shows up on the inside of your home, it has already been getting in for a long time — and it has taken the scenic route through your roof timbers, your insulation and your plaster to get there.

Almost none of these problems begin where you notice them. A damp wall is often a blocked gutter. A stained ceiling is usually a slipped tile or tired & weather-beaten lead. A musty corner can be a single perished joint in a rainwater pipe two floors up. The cause is sometimes small, simple and easy to ignore. The consequence, left long enough, is none of those three things.