New sockets in lathe & plaster walls? Extending cables?

Sorry if this has been already been asked but...

1) Am needing to re-route a couple of sockets (they're on a stud wall which is being removed) - but the only walls in the room then will be old lathe-and-plaster over sandstone.

Now my plan is to lift floorboards and run cables along the joist to the wall (not yet sure where they've come from), and then run them across the joists (drilling holes) until we're below where I want the socket.

But then what?

In other rooms in the house the sockets are the surface mounted ones, but don't look particularly good - my father suggests this is because it's not possible to fit recessed ones if its lathe & plaster - is he right? Am I really going to have to cut out the plaster to run the cable up the back and then reinstate?

2) If the existing cables aren't long enough whats best way of extending them - was planning to use a terminal block, tape it up well, and fix to side of joist?

You can't fit flush sockets into lath and plaster, because as soon as you start making holes, the plaster will crumble, the laths will move as you try to cut through them and you will end up with a huge hole where the wall used to be.
If you want flush ones, you will have to remove a section of the wall and fit a piece of plasterboard instead.

tullula said:

was planning to use a terminal block, tape it up well, and fix to side of joist?

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No. Use a proper junction box if the joint will be accessible (it probably won't be). If not accessible, crimp or solder the cables.

If you are careful, you can cut a dryline box into the lath using a padsaw, but expect a bit of crumbling nearby, not actually sure how good an idea it is with a socket tbh, with plugs being inserted and removed, it might crumble at a laster date.... if you can find an upright, cut a standard metal box in at that point, and sink it into the upright using a wood chisel (don't remove too much though)

And folow the other guys advice on joining cables

You have two problems here: getting a solid fix for the back boxes and running the cables up to them. Adam_151 is spot on about finding an upright. I always do this in stud partition walls. The cabling might not be so easy. It all depends upon how much clearance you have between the laths and the sandstone. You are looking for a continuous vertical gap between a wall that is naturally uneven and the ridges of plaster behind the laths. A lot will depend upon how thick the uprights are.

To find an upright you can use careful tapping or search for nail heads with a metal detector - or both. When you think you have one, drill a series of small (I use 5/64") test holes to find its edges. Next, drill a larger hole through which you can pass a small weight on the end of a piece of fishing line. If it goes down to the floorboards you're in luck, though you might have to cut upwards through a board if they go right up to the wall. Obviously, if you do get your line through you can use it to pull something stronger and then pull the cables in.

Cut the hole for the box VERY carefully. Drill holes at the corners first and then use a fine-toothed saw that cuts on the back stroke. A jigsaw blade will do nicely. As an added precaution, hold a straight edge against the plaster and cut along it, not so much to get a straight line as to support the plaster and prevent crumbling. For a real belt and braces job, cut a template hole in a piece of plywood and screw this through the plaster (pre-drill the holes) to the upright. You can re-use this jig many times.

If, as is likely, you have to sink the box partially into the upright, drill multiple holes to the correct depth with a flat bit then finish off with a chisel. Watch out for stray nails. There's always one lurking out of sight just waiting to wreck your best chisel.

In my experience i've always found it best to measure the height of your socket and mark it out. Then using a pad saw find the gap in the lath just above and below your socket and cut it out all the way to the timbers holding the lath either side of your new socket position. You then need to cut the lath out completely leaving you a hole a similar hight to your socket and as wide as the studs. Then fix your socket box to the wall using timber to pack it forward to the desired depth with a bit of timber either side of the socket box. Fit a bit of plasterboard or mesh either side of the new socket box and skim up the hole. The advantage with this method is that you never put stress on the surrounding lath and plaster when putting plugs in to the socket.

Remove all the lath and plaster, expose the sandstone walls, clean them up, tidy up the pointing, get a few boxes of Kleenex and invite RF to do his thing.

There's always one lurking out of sight just waiting to wreck your best chisel.

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I no longer have any best chisels.