Fixing socket to plywood panel

hippo49 · 8 Apr 2009

I have plywood panelling on the side of my stair and want to install a flush socket on it. There is moderately good access to the back side of the panel from the solum under the stair. I have read that I should not use a metal box for fire safety reasons but instead should use a drylining box. I haven't come across these before but they seem to have lugs that extend out from the side of the box and tighten against the back of the plasterboard (in the normal case of use with plasterboard).

The plywood appears to be about 8 or 9 mm thick but I can't tell for sure until I drill into it, which I don't want to do until I know I'm going ahead with this!

My questions are:
Would a drylining box be safe and suitable for mounting the socket on the plywood? Btw I live in Scotland (mention that in case the regs are different in this respect).
Would the lugs grip the plywood adequately or do they require to dig in as they might into plasterboard?
Do drylining boxes have knock-outs for the cables just like metal boxes?

Thanks.

ColJack · 8 Apr 2009

yes
should do, might need some packers if they don't pull up tight..
yes..

hippo49 · 8 Apr 2009

Thanks, ColJack. Straightforward answers to all the questions! I'll go and look for a drylining box now.

cabinman · 8 Apr 2009

I have read that I should not use a metal box for fire safety reasons

surely, the plywood would burn through, before the metal box did?

and a drylining box would melt, as its made of plastic?

ban-all-sheds · 8 Apr 2009

hippo49 said:
I have read that I should not use a metal box for fire safety reasons but instead should use a drylining box.

I don't know where you read that, but you should stop looking there.

wingcoax · 8 Apr 2009

If you did use a metal box what wood(sic) you fix it to?

hippo49 · 8 Apr 2009

I can see why you are puzzled but I didn't know that drylining boxes are made of plastic. Can you get metal drylining boxes?

I read about the suggestion of using a drylining box here:
//www.diynot.com/forums/viewtopic.php?t=30865

I used the term "metal box" just to mean the conventional galvanised metal box I am familiar with. I had presumed that there must be some feature about "metal boxes" that makes them less firesafe than drylining boxes for using with wood. That was why I asked about knock-outs, thinking that perhaps a drylining box has a more sealed and therefore safer kind of cable entry.

As to where I would fix a metal box to, I suppose I'd have to fit a batten behind the socket aperture and screw the metal box on to that. (I have reasonable access behind the plywood from the solum below.)

Any more thoughts would be gratefully received.

wingcoax · 8 Apr 2009

Only joking! You use the type of box that is required for the job. There is nothing wrong with using a dry-lining box where there is a void behind the surface with nothing to fix a metal box to, plastic cavity boxes are not sealed and have easy knock-out points in the sides and the back.Use one by all means, just make sure you are within regulations.

powersurge · 9 Apr 2009

Hope you don't mind me jumping on the back of these answers, but I would suggest checking that the proposed new accessory fits properly over the dry lining box, (sometimes a problem when mixing different makes) reason being: I had previously used 2 in my home - perfectly fit for purpose but the switch and socket that were on them didn't fully hide the lip of the box, and you could see it on all four sides. Being somewhere I passed several times every day it annoyed the hell out of me and after a while I decided they had to go!
Just changed them for some with a smaller outer lip and it looks 100% better - of course better to do it right from the outset !

hippo49 · 14 Apr 2009

Thanks, Powersurge. I had the same problem of fit. The first switch/socket plate I bought (a brass effect one to go with the varnished plywood) didn't fit over the drylining box. You get so used to all these things being standard sizes and everything fitting everything else but this one didn't fit because the earth strap bar was near the edge of the face plate. The drylining box, being a bit smaller internally than a metal box (a fact I should have realised but didn't), fouled up on it. The second switch/socket plate I tried does not foul up but it has no lip and so I have the problem that you had - I could still see the white edge of the flange of the drylining box. However in my case the socket is in a darkish place and so all I did was "paint" round the edge of the flange with an indelible black marker pen - just something to take away the obviousness of the white. It looks ok for now. I'm not going to try a third socket plate!

Thanks to all for your advice.

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Fixing socket to plywood panel

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