Hang a neon sign or light box on a lath and plaster wall

Fit a neon sign or light box securely on a lath and plaster wall, wired safely, without cracking the old plaster.

LP-01Plan the job and check the weightRead the light box's instructions for its total weight and the spacing of its fixing holes. Pick a wall position away from damp patches, near enough to a socket for the transformer lead, and clear of any ceiling void pipework above. Lath and plaster is brittle, so plan on using the longest, thinnest fixing that will still take the weight, rather than a big chunky screw.

1 each · Tape measure

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1 each · Pencil

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LP-02Find hidden cables and pipes, and check your isolation pointsRun a cable and pipe detector over the whole fixing area before you mark anything, but do not trust it completely. Detectors miss cables that are deep, run in metal conduit, sit behind foil-backed plasterboard, or lie outside the normal safe zones, and old lath and plaster walls often have odd wiring runs. Find your stopcock now (usually under the kitchen sink) and check it turns, so you can shut off water fast if you hit a pipe. If there's any real doubt about what's behind the wall, isolate the relevant circuit at the consumer unit before drilling, and turn off the water at the stopcock before cutting into anything that could carry water.

1 each · Cable and pipe detector

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LP-03Confirm you actually have lath and plasterTap gently across the wall — lath and plaster sounds slightly springy and hollow over the timber laths, while solid brick or block sounds dead and solid. Drill a 3mm pilot hole in an inconspicuous spot: fine white dust with a thin sliver of wood confirms lath and plaster, flat grey dust with a hard stop means solid masonry, and a hollow gap behind a plasterboard-thickness sheet means the wall has been overboarded. If you find a stud wall or dot-and-dab instead, follow the matching fixing method in Step LP-06 rather than the lath and plaster one.

1 each · 3mm drill bit

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LP-04Find the timber uprights behind the lathsUse a stud detector or a magnet dragged across the wall to find the line of nail heads holding the laths — these mark the timber studs or noggins behind. Try to land at least one fixing point on solid timber, since screwing into a stud is far stronger than relying on the laths alone. Older walls usually have uprights every 400-600mm, so measure across to find the pattern before you mark your holes.

1 each · Stud detector

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LP-05Mark up and drill the fixing holesHold the light box's bracket against the wall, check it's level with a spirit level, and mark each fixing hole with a pencil. Drill a 3mm pilot hole through the plaster and lath at each mark, angling slightly if needed to hit solid timber where a stud is present. Drill slowly on a normal rotary setting; lath and plaster cracks easily under a hammer action or fast, forced drilling.

1 each · 3mm drill bit

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1 each · Spirit level

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LP-06Fit the right fixing for each pointWhere a fixing lands on a timber stud, drive a 40-50mm wood screw into the centre of the timber for a strong hold. Where it only catches the laths and plaster with no stud behind, use a plasterboard-rated toggle or spring fixing sized for the light box's weight — plain screws and plastic wall plugs pull straight through brittle laths. If your pilot hole test in Step LP-03 showed a different wall type: use a wood screw into the stud centre for plasterboard on timber studs; a self-drilling or toggle metal-stud fixing (never a wood screw or plastic plug, which strips straight through 0.5mm steel) for metal studs; a fixing long enough to reach the masonry behind the dabs for dot-and-dab; and a plastic wall plug (usually 6-8mm) with a matching screw for solid brick or block. Always check the fixing's packaging states a safe working load higher than the light box's total weight.

4 each · 40-50mm wood screws

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4 each · Plasterboard toggle fixings

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4 each · Metal-stud self-drilling fixings

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4 each · Wall plugs and screws (masonry)

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LP-07Don't rely on a metal stud fixing for anything heavy or that gets pulledIf your test showed metal studs behind the plaster rather than lath and plaster, remember a metal-stud fixing alone won't hold a large sign that gets knocked, or anything heavier than a light picture. Fit a timber noggin between the studs, or fix through to the masonry behind, before hanging anything substantial. Our own lath and plaster job is usually light enough for a rated toggle fixing, but check the manufacturer's weight figure against the fixing's rated load to be sure.

1 length · Timber noggin (50x50mm)

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LP-08Hang the light box and check it's secureLift the light box onto its fixings following the manufacturer's bracket instructions, and check it sits level with a spirit level. Give it a firm, gentle tug before letting go completely, to test the fixings are holding. If anything feels loose or the wall flexes, stop and re-fix with a stronger toggle or land it on a stud instead.

1 each · Spirit level

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LP-09Connect the light box to powerMost neon signs and light boxes plug into a normal 13A socket through their own transformer or driver — route the cable neatly and keep it clear of any walkway. Do not hardwire the sign into the fixed wiring or add a new socket yourself. Switch on and check the sign lights evenly before you tidy up.

RULES

KNOW THE RULES

Adding a new socket or connecting into the fixed wiring is notifiable electrical work under Part P of the Building Regulations in England and Wales. Plugging into an existing socket doesn't need this.

LP-10Clear up and dispose of dust and debrisVacuum plaster dust from the floor and skirting — lath and plaster dust is fine and travels far. Wipe down the wall around the fixings with a dry cloth to remove any remaining dust. Recycle the light box packaging and dispose of any lath or plaster offcuts safely.

1 each · Dust sheet

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