Fitting sockets in damp walls

[davetheglitz]

I've been asked to quote for a rewire of an old farmhouse with big damp problems - existing metal back boxes rotted out. Rising damp to 5ft. Customer does not want surface mount sockets - and will be replastering with lime plaster (it's a builder thing - my understanding is that it breathes so when drainage is sorted outside it will dry out). The customer is adamant that he will not be fitting dry lining to battens.

Anyone got any experience with this situation?

My plan is as follows:-

• All cabling to be fed from top down to sockets
  
• Fit plastic conduit surface mount boxes - but recess back into the walls. Due to wet /unstable walls I intend to bed them onto plasterboard adhesive.
  
• All cables channelled in and fed into back boxes via cable glands.
  
• Cables to be rough plastered in with plasterboard adhesive prior to finish plaster.
  

What do you reckon?

 

[PeatBog]

I would avoid any gypsum (spelling!) based products and they can expand with damp and blow off the plaster (or lime).

I think plasterboard adhesive and bonding coat are both gypum based?

Sand and cement is probably best?

 

[davetheglitz]

I would avoid any gypsum (spelling!) based products and they can expand with damp and blow off the plaster (or lime).I think plasterboard adhesive and bonding coat are both gypum based?

Sand and cement is probably best?

Thanks - makes sense. Quick setting sand/cement mix seems to be the order of the day. Does anyone know if a PVA mix would help?

 

[batty]

When I have done damp walls I have always used a very strong sand and cement mix to bed boxes in, you could use plastic boxes with conduit chased in. I always leave at least an inch of cement behind boxes. The jobs that I have done they have been tanked and an expensive waterproofer is put in mix.

Batty

 

[Bez]

Wouldn't oval conduit help, just a thought. Or you could go the whole hog and use round conduit and gland it in to the boxes.

 

[ianmacd]

If they are plastering after, why not just cover the cables in capping?

 

[batty]

If they are plastering after, why not just cover the cables in capping?

Not a good idea eventually the cables will fail with moisture.

 

[ianmacd]

Agreed if this was not a habitable dwelling that the damp problem will be sorted and the walls will dry out.

 

[Lurch]

Not a good idea eventually the cables will fail with moisture.

But the damp problem is being sorted so before the cables even notice the damp it should be gone.

 

[davetheglitz]

Wouldn't oval conduit help, just a thought. Or you could go the whole hog and use round conduit and gland it in to the boxes.

I did think about going the whole hog - but thought it would add a hell of a lot of channelling - hence the idea of using the compression glands as an entry. The oval conduit might be good idea as securing cable to an unstable wall might be a bit awkward.

 

[batty]

Agreed if this was not a habitable dwelling that the damp problem will be sorted and the walls will dry out.

I think I would still rather use conduit easy to work with and easier to rewire if necessary.

Batty

 

[davetheglitz]

But the damp problem is being sorted so before the cables even notice the damp it should be gone.

In an ideal world - but personally I've got my doubts!

 

[batty]

In an ideal world - but personally I've got my doubts!

My thought too.

 

[ianmacd]

If the damp isn't sorted then they will never get sign off from labc anyway.

 

[Apache]

If the damp isn't sorted then they will never get sign off from labc anyway.

They might in summer

 

[davetheglitz]

I think I would still rather use conduit easy to work with and easier to rewire if necessary.Batty

You might be right - though hopefully no-one will be re-wiring in my lifetime. I'll suss it all out when I do the site visit (the job's in Wales for a family friend - long way from Cornwall!). Thanks for the help.

 

[Lurch]

If the damp isn't sorted then they will never get sign off from labc anyway.

What sign off?

 

[davetheglitz]

If the damp isn't sorted then they will never get sign off from labc anyway.

Sad to say - not my concern. However - I've never really understood the authority of the LABC. They own the existing property and are improving the drainage - but it might take years to dry out even if they have got the diagnosis right. Are the LABC going to say that you can't live in your own house until it dries out? As they don't intend moving does it matter if the LABC don't sign it off?

 

[kme]

As regards your original post Dave - I`d prob. mix some PVA in with the fastset.

Other option can be fast setting floor tile adhesive

HTH

KME

 

[PeatBog]

I'ved used flexible conduit a few times both with singles and as extra protection for twin & Earth. The 20mm glands fit into a normal metal backbox but best with 35mm deep boxes. You normally have to trim the gland back to the nylon nut to give yourself enough space in the box. The flexible conduit can be made to fit snuggly against a wonkey wall. The polypropylene (if undamaged) will be waterproof. However, it is much more effort that tacking some twin & Earth up the wall!!

The stuff I've used is called Easi-flex from www.cablecraft.co.uk