For a roofer, an attic is what an X-ray is for a doctor. What you see as a cluttered space with belongings and insulation is a record of every time water has come through the roof.
And you can read a good part of that record yourself. Take a good torch, a phone for photos and half an hour. What you find will save the roofer a whole search later.
Four marks and what they mean
Water rings on timber. A light edge around a darker centre. Each ring is a time when water collected and then dried again. Several rings means a recurring leak, so weather-dependent.
Limescale or salt streaks. White, grainy streaks on timber or brickwork. Water that has come through brickwork or mortar carries salts with it and leaves them behind when it dries. Follow the streak upwards and you will reach the source, often a chimney or wall junction.
Rust at nails and screws. A rust ring around a nail point means moisture regularly gets there. A row of rusty points shows a path the water takes.
Dark, soft or fluffy timber. Beyond a mark: here the damp has been present for longer. Push with a screwdriver. If it gives, the roof boarding is affected, see
replacing roof boarding.
“On a roof, water never runs straight down. It looks for the path of least resistance, and that path is drawn on the timber.”
Fouad, owner of Astrodak Service
How to follow the trail in the right direction
The rule is simple: marks point upwards. Start directly above the spot where it is visible indoors, and then work your way up the slope. Look especially at the top of the rafters and at the place where a rafter meets the roof boarding, because that is where water likes to run.
Do not lose the trail if it stops for a while. Water can run some distance over the membrane without leaving a mark and only reach timber again further on. In that case, keep going up and look for the next ring or streak. If you end up at a chimney, a valley gutter, a roof window or a penetration, you have almost certainly found the source.
Reading the marks
from the bottom
to the top
Several rings
recurring
weather-dependent
Not sure about the right approach?
I would rather come and look at your roof with my colleagues first than come up with a solution from a distance. During the free inspection you hear what is really needed, even if that is less than you thought.
What to photograph and write down
Overview and detail. First a photo that shows where you are standing, then the close-up. Without an overview, a detail photo is impossible to place later.
With a reference point. A roof window, the chimney, the hatch. Then the photo shows where in the roof this is.
Date and weather. Note the date and whether it was raining or windy that day, and from which direction. See
leaks in driving rain.
What is dry and what is wet. Feel the roof boarding and insulation with your hand. Where it changes from damp to dry is a clue to the edge of the problem.
When to leave it to a roofer
If you find no marks but water is still coming in, if the trail runs on under the insulation, or if the insulation covers the roof boarding completely so you cannot get to it. With a roof insulated from the inside, the underside of the roof boarding is not visible, and then this method cannot be used.
In those cases we come and work with a water test or moisture measurement. How that works is explained in
tracing a leak. And if you have found the marks: send the photos with your request, then I often know where to look before I arrive. See
free roof inspection.
What you should not remove before someone comes
The marks themselves. It is an understandable reflex to dry a damp spot or wipe away growth, and it is exactly what you should not do. Those rings and streaks are the only information there is about where the water has run.
The same goes for wet insulation: leave it where it is until someone has looked at it, because the place where the damp stops tells you how far it has got. Taking photos is of course always fine, and it is even the best preparation there is.
Frequently asked questions about marks in the attic
