Very mild damp

[londonbairn]

We have very, very mild damp on one of our walls in our extension. We noticed as one of our RCDs started tripping very infrequently, and on taking a socket off, we noticed one was slightly damp. After some tests and trial and error with the electrician, we are pretty sure we have isolated the cause.

As we wanted a new board done, we got a new one installed with RCBOs, with the offending circuit temporarily on a MCD. The socket is also dry now as we are using heating (the flow/return pipes run very near).

To fix this, we have a few options..one involves the Newton membrane with sealed backboxes, or we go the whole hog, lift the floor up, check damp proofing etc. This would be destructive as its a wood floor, but possible to do.

What is the best way around this? Feels like I am chucking a lot of money at a small problem. The damp itself is so small you cannot see it on the wall. It's only "in the wall". Also the portion that has it neighbours onto the neighbouring extension, so the theory is that when they put their extension in, their damp proofing is above ours and they didn't properly mitigate for this.

Are there alternatives that are most cost effective?

 

[boxman2000]

All I know is that it doesn't take much dampness to do big damage over a period of time. Best to get it sorted properly.

 

[londonbairn]

What is the best way? Pulling back to foundation and fixing it beyond any shadow of doubt?

 

[boxman2000]

Have you costed up the options? Are you 100% certain the cause has been identified?

Causes of dampness and leaks can be a nightmare to identify. My first house had terrible damp issues and we were getting quotes of £10's of thousands of pounds by specialists. They were telling us we had to basically rip up all the floors, install dampcourse (they couldn't tell if there was one or not) and basically having to put in controlled circulating fans into each of the rooms for airflow. It turns out I sorted it myself for free - the previous owner had put down some new gravel around the outside of the property which was higher than the damp course. I simply reduced substrate level and problem resolved.

My point is I would really make absolutely certain before spending money.

 

[londonbairn]

Agree, to be honest we are 95% sure but I want to be 100% sure. Our builders are family friends so quotes are reasonable. Problem is it is a party wall. I might ask the neighbors actually if they have issues, but the evidence so far points to their DPC being higher than ours.

I guess the best way would be to break out part of the wall to inspect what is going on exactly? Another potential problem is their extension isn't as long, so maybe they have something going on in the corner of theirs (e.g. guttering etc); will check

 

[bitslice]

I guess the best way would be to break out part of the wall to inspect what is going on exactly?

Yep, I'd do this.

(as an aside while we are on the topic, injectable damp proof courses are often a con)