Plastic capping and boxes when damp

[sharpspark]

The house we are doing up has damp walls and will be rewired after dpc has been injected and new floor and dpc laid. The damp man has advised that plastic capping and plastic knock-out boxes should be used downstairs as the damp will cause corrosion of galvanised stuff due to salts in the bricks. This is certainly very evident in some of the current capping. I nipped down to the local electrical trade outlet and they stock neither as there is no demand for them. Does anyone have any comments on this advice? I'm not keen on plastic capping because of limited protection but don't see a way round it. Does anyone know where you can get plastic flush boxes mail order - couldn't find them in Screwfix or TLC, other than dry lining boxes. We are planning to use Platon breather membrane on the walls with standard plaster on top.

 

[il78]

What are you paying the damp proof guy for? If the damp goes, so will the corrosion...shouldn't it?

I've on ever seen:

Plastic Pattresses
Plastic Conduit Socket Boxes
Plastic Dry Line Socket Boxes

 

[masona]

What are you paying the damp proof guy for? If the damp goes, so will the corrosion...shouldn't it?

Yes,100% correct

 

[ban-all-sheds]

Immediately? Won't it take a while for what's there to dry out?

'spose one of these could help

 

[sharpspark]

All general guide lines I've seen give approx 9 months for a solid 9" wall to dry out so I guess that gives time for corrosion and it was certainly damp to start with. Interestingly we have plastic knock-out boxes in our present house (approx. 27 years old) but never seen them anywhere else. Long time foreman from specialist building firm that does things like National Trust work also assumed we'd be using plastic. I feel like metal would be OK but don't want to go against advice if it's from peoples long experience. Some of the removed capping was badly corroded and none of it was near floor level where new flush sockets will be.
Any idea why I didn't get emails to say replies had been posted after I had ticked the box?

 

[ban-all-sheds]

Have you asked said long-time foreman where you can get plastic boxes?

Plan B might be to cut very neat holes so that the boxes can be fixed by screws, and not need any plaster/filler around them, and replace them in a year once the walls have dried out.

 

[masona]

Could you not treat the metal box with a heavy duty rust-proof paint or have them hot dip by a company ? There are many good brands, you could try the boat shop as they specialise paint for metal in sea salt water...........

 

[ban-all-sheds]

That might be expensive. Regular galvanised ones ought to last a year, especially as the walls will be drying out all the time?

 

[loftus75]

I suspect the foreman is thinking of dry lining plastic boxes or surface mounted pattresses. However if you use a dehumidifier this should accelerate the drying out period and the metal boxes should be able to tolerate the moisture for the required period.

 

[masona]

I suspect the foreman is thinking of dry lining plastic boxes or surface mounted pattresses.

I did think of that earlier,maybe it's possible to screw the dry lining plastic box into the wall somehow?

 

[loftus75]

I did think of that earlier,maybe it's possible to screw the dry lining plastic box into the wall somehow?

It is possible to do this, though you'd have to allow for the odd shape and the fact that the plactic box would not have the structural integrity of a metal box.

 

[sharpspark]

Thanks for all this, I had wondered about putting paint on, maintaining earth integrity of course. It would be fairly quick to do as looks aren't exactly important! Changing after a year doesn't sound good as cutting neat holes in these variable bricks is unlikely. Capping could likewise be painted but more messy so probably have to use plastic for that but protection not so good. It could have been plastic surface mount that the foreman was talking about, unfortunately he's not contactable at the moment.

 

[masona]

Just thought of something else,you could use Denso tape round the metal box,it can be a bit messy but you only got to do it once or how about wide insulation tape and then forget about it.

 

[supersparks]

how about, getting a weatherproof box(plastic) recessing it like you would a normal box, running the cables down to it in hi impact plastic conduit, then mount your metal box inside that. then it has a water guard arround it
something like this, just remove the lid, they come in all sizes and depths http://www.tlc-direct.co.uk/Products/GWBX442.html
AR

 

[sharpspark]

Hmm, sounds expensive the number of sockets we're putting in! Maybe a layer of duct tape will do the job. Could do the capping as well. I'm prepared to make some effort rather than surface mount everything.