Damp problems in sockets... solutions?

[HappyHippyDad]

I have a customer who lives in a grand old house which suffers from damp.

The ground floor sockets (2 different circuits) IR test at around 0.3Mohms L/N-E. This was actually 0.01Mohms but I have already done some fault finding and managed to improve it.

Most of the back boxes are very rusted and flaking to bits with moisture inside them. As stated, I have done some improvements to the sockets and boxes but this has only managed to get the IR up to 0.3Mohms (L/N-E). I have looked thoroughly for any more sockets/FCU's that I may have missed but I now feel the remaining fault(s) are within the walls, even though this doesn't make sense as I can't see how moisture would have got inside the cable (Its black/red metric PVC).

I think the existing cables have metal capping within the damp walls, but again, even if this capping is rusting I cant see how it will affect the PVC covered cable. The wiring is approx 25 years old

My questions are..

1. What can you do about damp? It's pointless to rewire as the damp problem will still be there. Are there ways to protect the boxes and sockets from damp?

2. What are the solutions if I cannot raise the IR above 0.3Mohms? I'm guessing I have to map out the entire circuit, and find every single fault, but then what? It's an immaculate house, surface trunking not an option, new cable in wall not really an option as existing damp problem already somehow affecting cables in walls (unless some kind of cable joints in walls which are affected).

3. Are these designed to be installed in the wall? 2 Gang 35mm PVC Flush Box Round Corners with 20mm Conduit KO White (Sold in 1's) - https://www.cef.co.uk/catalogue/products/1063228-2-gang-35mm-pvc-flush-pattress-box-round-corners-with-20mm-conduit-ko-white

Usually fault finding is easy. 1 fault, bit of IR testing, fix fault. In this case there are faults everywhere and not just in the actual sockets!

 

[Jm1980]

Sounds like significant damp if it is rusting things noticeably. I guess they really should look at getting it treated.

Regarding the circuit, id be tempted to map it out completely, disconnect all sockets/FCu's and everything so you just have the cable ends sticking out of the wall..........then do your continuity and IR tests on each leg noting the results. From this you can build up a better idea of the faults that exist............who knows, it may only be 1 troublesome leg where you might be able to re-route that leg in a bit of D-line on the surface or something that avoids damaging the decor.

I think you really need to find the issues on the circuit first off. Also dont discount something random somewhere giving odd results........seen plenty of outside lights spurred straight from the back of a socket that were giving issue's.

 

[DPG]

I can't imagine any flush mounted accessories would be possible without sorting the damp issue first. Sounds a nightmare.

 

[HappyHippyDad]

I can't imagine any flush mounted accessories would be possible without sorting the damp issue first. Sounds a nightmare.

I'll let the customer know that they are fxxxxx then

 

[DPG]

I'll let the customer know that they are fxxxxx then

Sorry, yeah I wasn't much help there was I. Just thinking out loud

 

[telectrix]

ventilationis necessary in old houses. might also help investing in a de-humidifier.

 

[Pretty Mouth]

Rising damp is usually treated by injecting a chemical DPC into the wall, and then rendering to a height of 1m up the wall with a damp resisting render. Belt and braces.

However I have found when cutting into such walls, that they can still be damp behind the render, so perhaps the chemical DPCs aren't all they're cracked up to be. The render traps the moisture in the wall, resulting in permanently damp brickwork, whereas it might have dried out somewhat had it not been there.

So getting the place damp proofed may not be the silver bullet.

If I were to rewire a job like this, and the client wanted everything chased in, I would use plastic backboxes such as the one you linked to above (it says flush mount so I assume fine for this), and plastic conduit glanded in. Where bedding in any backboxes etc, I would use a strong 3:1 sand to cement mix, with a generous splash of waterproofing admix such as this (I have used this mix to patch repair damp-proof render such as above, and it works well):

Sika Proof Liquid Waterproofing Admixture - 5L | Wickes.co.uk

Sika Proof Liquid Waterproofing Admixture - 5L

www.wickes.co.uk

 

[timhoward]

I think getting the customer to call in a damp specialist is best advice. I did this once and they injected a DPC. It was an entire redecoration job but seems to have worked.

Only other thought is doing something unusual and extreme like running conduit outside and through to surface mounted accessories

 

[Petej999]

I have a customer who lives in a grand old house which suffers from damp.

The ground floor sockets (2 different circuits) IR test at around 0.3Mohms L/N-E. This was actually 0.01Mohms but I have already done some fault finding and managed to improve it.

Most of the back boxes are very rusted and flaking to bits with moisture inside them. As stated, I have done some improvements to the sockets and boxes but this has only managed to get the IR up to 0.3Mohms (L/N-E). I have looked thoroughly for any more sockets/FCU's that I may have missed but I now feel the remaining fault(s) are within the walls, even though this doesn't make sense as I can't see how moisture would have got inside the cable (Its black/red metric PVC).

I think the existing cables have metal capping within the damp walls, but again, even if this capping is rusting I cant see how it will affect the PVC covered cable. The wiring is approx 25 years old

My questions are..

1. What can you do about damp? It's pointless to rewire as the damp problem will still be there. Are there ways to protect the boxes and sockets from damp?

2. What are the solutions if I cannot raise the IR above 0.3Mohms? I'm guessing I have to map out the entire circuit, and find every single fault, but then what? It's an immaculate house, surface trunking not an option, new cable in wall not really an option as existing damp problem already somehow affecting cables in walls (unless some kind of cable joints in walls which are affected).

3. Are these designed to be installed in the wall? 2 Gang 35mm PVC Flush Box Round Corners with 20mm Conduit KO White (Sold in 1's) - https://www.cef.co.uk/catalogue/products/1063228-2-gang-35mm-pvc-flush-pattress-box-round-corners-with-20mm-conduit-ko-white

Usually fault finding is easy. 1 fault, bit of IR testing, fix fault. In this case there are faults everywhere and not just in the actual sockets!

PVO??

 

[7029 dave]

External walls in old houses suffer this quite a lot, also chimney breast walls can be damp, rusting back boxes. I would advise getting a builder round to address the damp and treat, then replace all the rusting boxes and sockets if need be, this will help improve the IR big time.
Maybe minimize sockets on external walls if practically possible.