Roof Leaking in Heavy Rain Only: What That Tells Us

Wind driven rain at flashings and verges

The most common answer. In ordinary rain water runs down the face of a chimney or a gable verge and away. In driving rain it is pushed sideways and upwards behind a lifted flashing or into an open verge joint. Note which direction the wind was coming from when it leaked, because it tells us which elevation to look at first.

Gutters and valleys overwhelmed by volume

A gutter that copes all year can overshoot in a downpour once it is half full of moss and grit, and the water then runs back under the eaves and onto the wall plate. Valleys behave the same way when debris has built up at the bottom. Neither is a hole in the roof, both look exactly like one from inside.

Hairline cracks and porous tiles

A fine crack in a tile or a porous old concrete tile only passes enough water to show up when it is being soaked for hours. That is why the stain appears after a long night of rain and not after a shower. Frost damage over several winters is the usual reason a tile turns porous.

Ruling out condensation first

Before we go hunting, it is worth checking that the damp is not condensation being blamed on the weather. Condensation shows grey and mouldy, is worst in cold spells and appears across the loft rather than in one trail. Rain related leaks stain brown and follow a path. We check both at inspection so you are not paying to fix the wrong problem.

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