Penetrative damp

[darlingsweetpea]

Hello, I have a damp external wall and it is driving me crazy. The wall was bone dry during the summer and the second it rains, the wall is wet again.

I've replaced the window, the render outside is brand new and there is nothing wrong with the roof. I have had 3 roofers round and they have all said the roof is fine.

So what can it be or what can I do? I'm honestly at a loss now and totally fed up as this was a preexisting damp problem when I bought my house in January.

Thanks!

Does the wall have a damp course?

Has a previous owner paid for cavity wall insulation that has breached the damp course?

Is the wall cavity filled with debris that is breaching the damp course?

Its a first floor bedroom and there is no cavity wall insulation, the cavity is empty as I saw when I had a new window fitted.

Would you have a damp.course on the first floor?

What about the guttering? Any gaps?

No, no damp course up that high.

I had a damp bedroom wall during a cold spell, the winter before last, couldn't work it out. I could see moisture on the inner wall of a centrally heated, first floor bedroom.

I guessed it was condensation, so I went outside, put up a ladder and looked closely at all the brickwork along that stretch. There had been something attached to the exterior wall before I owned the house (tv ariel bracket?) and there were three large holes in the mortar which no-one had bothered to fill in.

The cold air was getting into the cavity, chilling the inner wall, and causing inner condensation. I filled the holes and the problem went away.

Could it be that?

You had the wall rendered or the previous owner?

That pattern (bone dry in summer, wet as soon as it rains) does sound like water getting in from outside rather than condensation, so you're right to keep looking. On a first floor wall with a new window and new render, the usual suspects I'd check are:

The window sill and the seal around the frame. If the new sill doesn't stick out far enough or has no drip groove underneath, water runs back into the wall below it. Missing sealant at the corners does the same.

Where the render meets anything else: window reveals, the eaves, pipes, any brackets. Hairline gaps there let water in behind the render and it then shows up inside.

Gutters and downpipes in heavy rain specifically. Go out in a downpour and watch for an overflowing gutter, a leaking joint, or water pouring down the wall.

The lintel/cavity tray over the window. If there's mortar or debris bridging the cavity around the new window, water can cross to the inner wall.

Note exactly where the damp patch starts (under a window corner, top of the wall etc) as that usually points straight at the cause. A builder with a ladder and a hose, wetting one section at a time, can often find it in an hour or so.

How high up the wall is the wet patch? Inside or out? Post some pics please. I would suspect a blocked or faulty gutter,