The brown stain on the ceiling is almost never under the hole. That is the first thing to understand before opening anything up — and the reason why so many ‘failed’ repairs are nothing of the sort: they were simply done in the wrong place.
How the water travels
Water gets in at a high point, drops onto the roofing underlay or a rafter, then follows the slope of the timber. It can run two or three metres along a purlin before finding a knot, a notch or a drilled hole to drip through. That is where the stain appears, not directly below the fault.
Another trap: the leak that only shows up in a steady westerly wind. Vertical rain is not enough to reveal it; you need driving rain that pushes up under the tiles. That is what explains the “intermittent” leaks you can never reproduce on the day of the visit.
The most common points of entry
- The flashing around a chimney stack: the first suspect, by a long way.
- The valley between two slopes, especially if it is old or clogged.
- The joint around a roof window, when the flashing kit does not match the roof covering.
- A shifted or cracked tile, sometimes invisible from the ground.
- A flat-roof waterproofing upstand that has shrunk back.
- A gutter that overflows and backs up under the first row of tiles.
The method that avoids opening up at random
We start with the facts: since when, in what conditions, with which wind. Then a visual inspection of the loft and the roof. The thermal camera then maps out the damp area inside the wall — it does not show the water, it shows the temperature difference the water creates.
Finally comes the water test: we spray zone by zone, from the bottom upwards, waiting between each zone. The moment the leak reappears marks the point of entry. It takes longer than a quick look, and it costs far less than a repair carried out on guesswork.
Watch out for condensation
Drips under the roofing underlay, a faint stain in winter, a loft that ‘weeps’: it is not always a leak. A poorly ventilated loft or a punctured vapour barrier produces exactly these symptoms. The treatment is nothing like the same, and you have to tell them apart before charging for a repair that changes nothing.
