Almost everyone who calls me about a leak tells me where the stain is. That makes sense, because it is the only thing you can see. But the place where the water comes out of the ceiling is almost never the place where it got in.
Water that gets through a roof doesn't go straight down. It runs over the membrane, along a tiling batten, over a beam, sometimes for metres, until it finds a hole or a seam and can get down. I've had leaks where the stain was in the living room and the cause was at the chimney on the other side of the roof.
How tracing works in practice
I never start on the roof. I start in the attic, because that is where the evidence is. On the underside of the boarding and on the beams, water leaves traces that tell you where it came from.
First follow the trail back. Damp rings on timber, lime streaks on a beam, a faint trace on the membrane. Those traces always lead upwards to the source. This is the most important half hour of the whole job.
Then the four usual suspects. In most homes the leak is in the lead flashing at the chimney, in a valley gutter, at a roof window or dormer, or at a roof penetration. Those are the places where two materials meet.
Then the roof surface itself. Broken or slipped tiles, loose ridge tiles, a torn membrane. Less often the cause than people think, but it happens after a storm.
If in doubt, a water test. Wetting the roof bit by bit from the bottom up while someone watches in the attic. Slow work, but it gives certainty instead of a guess.
“The stain on your ceiling tells you where the water came out. The attic shows where it got in.”
Fouad, owner of Astrodak Service
What you can already establish yourself
You don't need to go onto the roof. What you can do is note down three things before anyone comes, because that speeds up the search considerably.
When it appears. Straight away during the rain, or only a day later? Straight away points to a hole or a failing detail. Hours to days later points to moisture that first collects in the insulation layer, or to
condensation.
In what weather. Only in strong wind from one direction? Then it is often in a connection that can't cope with driving rain. See
leaks in driving rain.
How much water. A stain that slowly grows, or drips you can count? That difference decides whether it is an emergency.
What is above it. Look in the attic directly above the stain and photograph what you see. Even if it looks dry: that is information.
A leak? Do not let it spread.
A leak you leave for a season usually costs ten times as much in follow-on damage. Call or send a message: you will get an answer today, from me personally, not from a scheduler.
Why acting quickly really matters
A leak you leave for a season is a different problem from a leak from last week. Moisture that soaks into the roof boarding makes the timber soft. Insulation that gets wet doesn't recover and has to come out. And in a damp attic, mould spreads faster than you would expect.
One leak or several weak spots
On a fifteen-year-old roof, a leak is almost always one defect: a flashing, a tile, a penetration. On a roof of thirty years or older, it is usually the first of several weak spots. That is why I don't just check the spot above the stain but the whole roof surface, and I tell you what else I see coming.
Sometimes the conclusion is that one repair is needed and you'll have peace of mind for years again. Sometimes the conclusion is that the roof has reached the end. Which of the two it is, you can read in
repair or replace. We trace leaks in Vught,
Den Bosch,
Boxtel and the surrounding area, see the
page on roof leaks and emergencies.
Frequently asked questions about tracing leaks
