There are few things more quietly maddening than a damp patch that keeps coming back.

You dry it out. You repaint it. Three storms later it's back — same corner, same tide-mark, same sinking feeling. And it doesn’t stop there – it only seems to happen when the wind blows a certain direction, or there’s a blue moon…. And because water travels in ways that don't respect logic (or plasterboard), the wet patch on your wall is very often nowhere near the actual point of entry.

At Upcycle Interiors Ltd (UIL) we investigate water ingress across Weymouth, Portland and Dorchester more often than almost any other call-out — and on our exposed stretch of the Dorset coast, with salt-laden horizontal rain and freeze-thaw doing its worst every winter, that's no surprise. This post covers the main ways water gets into a building, explains the unsung hero of cavity wall construction — the cavity tray — and walks you through a recent investigation in Rodwell, Weymouth, where the camera told us something the wall had been hiding for 20 years (literally).