Leak in external single-story annexe wall Damp can be a major issue in the home. Find answers to questions or post your own here.

[alex879]

First time poster and DIY novice here, so please excuse my ignorance!

I recently noticed a leak coming through my single-story annexe wall. The water is coming out of a wall-mounted plug socket (not chased in).

After making the socket safe, I went round the back to the external wall to check for damage.

All mortar seems adequate except the tiny vertical strip shown in the image below. The mortar seems to be absent entirely, though it looks/feels like there's more brick underneath.

The strip of absent pointing *roughly* aligns with the location of the leak. No pipes run through this wall.

The other potential culprit is weathered copings on the parapet of the flat roof above. Presumably they could be letting water into the wall cavity? But if that was the case, I'd assume there'd be a larger damp patch. This leak seems to be only coming through the plug socket. Moisture readings elsewhere on the wall are about 5-12%.

What do you all reckon? Is this bit of absent mortar likely to be the cause? All suggestions and comments welcome.

[stoneyboy]

Hi alex879,
The hole in the external mortar is unlikely to be the source.
Whilst you say the socket is not buried what about the supplying cable? If this has been run through the cavity and water is getting through the parapet wall, the cable may be acting as a wick. Trace the cable.
Regards S

[alex879]

That makes total sense - thank you! A builder came to look at it today and also thought the coping stones leaking into the cavity are the likeliest culprit. He has quoted to repoint them and apply StormDry to the walls and coping stones.

An electrician is visiting for a different job on Monday and has agreed to remove the socket and trace the cable. Should get to the bottom of the problem.

[stoneyboy]

Hi alex879,
Thanks for the update.
What you propose will not stop water ingress through the joins between the coping stones when they crack with the inevitable movement.
Suggest the coping stones are removed and a DPC fitted underneath them covering the whole width of the cavity wall. Lead would be ideal so it can be dressed down the wall.
Regards S

[alex879]

Brilliant, I will get the builder to remove the stones, check for a DPC, patch it if existent and install one if not. Thanks so much for your advice.