Help installing electrical back boxes!

[GSDog]

Hi all.

I'm in the process of renovating a house with my brother and he insisted that we install all the flush mounted back boxes for the electricians to save money.

I've never done this before in my life so it's been a bit of an experience. The back boxes are now in place but I'm not sure how to secure them properly.

We went a little too deep when cutting out the back boxes for a couple of them and so we filled the holes with plaster to allow us to screw the back boxes in. However, the plaster has now set and I cannot remove the back boxes to drill holes and put the wall plugs in to screw them in.

Do they need to be screwed in or is it OK if they're secured with plaster behind the boxes?

I'm not sure how to secure them now and the electricians are starting on Monday expecting them to be done.

Any help would be appreciated.

 

[holmslaw]

..

 

[bernardgreen]

Relying on plaster is not a good idea. Especially after a few weeks of plug being pulled out pushed in. Metal warms up expands, plaster doesn't expand so much.

If you really cannot get them out then drill one hole through the centre of the box. Use a drill large enough to get the rawl plug through the hole in the box. Then use a cup washer under the head of the screw if the hole is larger than the head of the screw.

 

[sparkwright]

You don't need to remove the boxes to fix them to the wall.

Use a 5.5 mm drill, and drill through the box fixing hole into the brickwork. Push a red plug into the hole, tap in fully so the plug is just past the metal box. Then fit the screw. Use two fixings if possible.

Be sure to fit rubber grommets where the cable enters the cable entry. If your brother says there's no need, ignore him.

Be sure all boxes are level. Use a spirit level. If they are crooked the sockets you fit may also end up crooked.

Be sure all sockets are at the same height, if you are out by an inch or so it can be very noticeable.

It would be a good idea to use pvc oval conduit or capping to protect the cables in the wall. Will protect cable whilst plastering, and may assist in future alterations to the wiring. Trust me, it can help if there's a problem with the wiring.

 

[GSDog]

Thanks everyone.

I've done what you said and drilled through the box fixing holes and fitted the rawl plugs that way, they are all nicely secured now.

Be sure to fit rubber grommets where the cable enters the cable entry. If your brother says there's no need, ignore him.

My brother didn't mention this. Would I be able to buy the rubber grommits from somewhere like B&Q?

EDIT: Is this what you mean? http://www.screwfix.com/p/pvc-grommet-open-pack-of-100/11833

It would be a good idea to use pvc oval conduit or capping to protect the cables in the wall. Will protect cable whilst plastering, and may assist in future alterations to the wiring. Trust me, it can help if there's a problem with the wiring.

I was going to leave that for the electricians to do since they're doing all the wiring, etc. I will ask them if they're using it though.

Thanks for the help.

 

[sparkwright]

Yes, that's the type of grommet. B&Queue will do them, or any electrical wholesaler. You, or the electrician if he is running the cables, need to fit them before the plastering is done.

It sounds like your electrician will probably supply and fit the grommets.