Socket Outlets - Fitting Flush Metal Box

When fitting a socket outlet, a backing box or pattress is fixed in place to house the socket and the wiring connections behind. Pattresses for flush mounted socket outlets in solid walls are generally made of metal.

Tools and materials for fixing flush mounted metal pattress

In this guide we show you how to fix the back box and insert the cable ready for connecting up the socket outlet

Flush Socket Outlet in Solid Wall

Mounting the metal box used for a flush socket outlet in a solid wall is a little more involved than those for surface mounted boxes or plasterboard boxes, but still not particularly complicated.

Metal pattress held level against the wall

1. Hold the metal box in position against the wall and, using a small spirit level, ensure that it is perfectly level.

Marking outline of metal box

2. Mark around the perimeter of the box with a pencil line. If you hold the edge of the pencil against the side of the box as you run it round it will give you an extra 2 or 3 mm clearance. This will make fitting the box a lot easier.

Drilling perimeter of hole for pattress

3. Having first checked that there are no cables or pipes below the surface near where you are cutting the hole, use a masonry drill to make a series of holes around the perimeter of your outline. Wear safety goggles and ear defenders while drilling into masonry.

4. If you have a depth-stop on the drill, set this to slightly more than the depth of the box. Otherwise mark the depth on the drill bit with a piece of tape wrapped round it, so that you can see when the appropriate depth has been reached.

Cutting the socket outlet recess

Drilling the wall for recessed socket box

5. Once the perimeter has been drilled, drill a grid of holes to the same depth throughout the internal area of the outline. This should make removal of the remainder fairly easy.

Cutting out wall with cold chisel

6. Using a cold chisel and hammer, trim out the hole as neatly as you can. Wear safety goggles and ear defenders while you’re doing this.

Wall cut out cleanly for metal box

7. The neater the cut out is, the less making good you’ll have to do later.

Checking the metal box fits flush

8.Once the hole has been cut out, check that the box will fit comfortably into the recess and sits flush with the surface of the surrounding plasterwork.

Chasing the Wall for the Cable

Conduit for cable held level for marking

9. Cut a suitable length of plastic conduit for the cable run in the wall and hold this in position against the surface. Mark either side with a pencil.

Chasing wall for cable conduit

10. Wearing safety goggles and ear defenders, use a cold chisel and hammer to chase out this cable run so that it’s deep enough to accommodate the conduit allowing for a decent layer of plaster over the top.

Cable entry blank knocked out

11. Take the metal box and knock out the most suitable cable entry point. This is best done by giving it a sharp tap with a small cold chisel and hammer.

Inserting protective grommet for cable

12. Line this to protect the cable by inserting a rubber grommet. These can be purchased as open or blind. For this purpose, the open ones are best.

Fixing the socket outlet box

Marking metal box fixing points

13. Insert the metal box into the recess you cut out and mark the fixing positions by drawing a pencil mark through the holes in the back of the box.

Drilling wall for fixings

14. Remove the box and drill the fixing holes with a masonry drill bit of a suitable size for the plugs you are using.

Inserting wall plugs for fixing metal box

15. Insert the wall plugs and tap them home with a hammer.

Inserting cables in conduit

16. Cut the conduit to length and feed the cable through.

Feeding cable into pattress through grommet

17. Place the conduit covered cable in the chase in the wall. Then feed the end of the cable through the grommet making sure you have made adequate allowance for trimming and connecting the conductors.

Fixing the metal box to the wall

18. Reposition the box back in its recess. Align the fixing screws. Hold the screws steady and use a cordless driver to tighten them. Make sure that the box is held firmly and stays level.

Making good around new socket box

19. Make good the chase and around the edge of the metal box before connecting up the socket outlet.

Wall made good around socket

20. Allow the making good to set then sand smooth with abrasive paper.

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