The conversation is almost always the same: there is a stain on the ceiling, somebody painted over it, the stain came back. It gets painted again, it comes back again. By the third round, the right question starts to appear — where is the water coming from?
Water travels before it shows
Water gets in at one point, runs along the top of the slab or through the inside of a wall, and comes out at the lowest or most porous point it finds. That point can be metres from where it got in.
That is why painting the stain never solves it: you are treating the exit, not the entrance.
Where we find leaks, in order of frequency
1. Details, not membranes
On a terrace, what fails is rarely the membrane in the middle: it is the detail at the wall, a short flashing, a threshold with no drip, or a badly sealed downpipe. The membrane is the easy part.
2. Silicone at the end of its life
In a bathroom, the silicone between the shower tray and the wall lasts a few years. When it opens, the water gets through and the neighbour below is the first to know. It is the cheapest repair there is and the one most often put off.
3. Blocked gutters and downpipes
Leaves, nests, grit. The water overflows and runs down the facade, getting in through any crack it finds.
4. Cracks in the facade
One fine vertical crack on a facade exposed to the south and the rain is enough to wet the inside wall after a single winter.
5. Condensation, which is not a leak
Dark patches in the corners of external walls, in winter, with mould. No water is getting in: it is the moisture in the house condensing on the coldest surface. That is solved with insulation and ventilation, not with waterproofing.
How we look for it
- We look from the inside first. In the loft, in the garage, on the ceiling of the floor below. The shape of the stains tells you which direction the water is coming from.
- We look at the weather. If the stain only appears with rain and wind from one direction, that points at a particular facade.
- We run a water test. One area is wetted at a time, in order, and then you wait. It is slow and it is the method that gives the right answer.
What not to do
Do not have a whole terrace waterproofed before you know where the water is getting in. It is the most expensive answer and, if the problem is a flashing, it will still be there after you have spent the money.
If you have a stain that keeps coming back, tell us where it is. We will come and look, and we will tell you what we found even if the answer is that it is not a job for us.
