Hang a heavy mirror on a lath and plaster wall

Locate solid timber behind your wall safely, then hang a heavy mirror securely and level, without cracking old plaster.

AB-01Check your wall type and gather your kitLath and plaster is old timber strips (laths) nailed to timber studs or joists, covered in a skin of lime plaster, usually found in houses built before about 1930. It feels slightly springy when pressed and sounds duller than modern plasterboard. Lay a dust sheet below the work area and clear furniture out of the way, since old plaster crumbs make more mess than plasterboard dust.

1 each · Dust sheet

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1 each · Tape measure

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1 each · Pencil

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1 each · Spirit level (600mm)

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1 each · Stud/pipe/cable detector

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AB-02Mark the hanging height and fixing pointsHold the mirror up (or get someone to help) and mark a light pencil line at the height you want the top edge. Use the spirit level to keep this line dead straight, then measure down from it to mark exactly where the mirror's rear fixing points or wire will sit. Double-check the two fixing points are level with each other before you go any further.

AB-03Find the timber behind the lath and plasterLath and plaster is almost always fixed to timber studs or joists, not metal ones, but confirm this rather than assume it. Run your detector over the marked area, then tap gently across the wall — a dull, solid knock means timber behind the lath, a hollow knock means you're between studs on the lath alone. Drill a small pilot hole at your marked point: fine pale dust means you've hit timber; if the drill drops straight through with no resistance, you've missed the stud and are only in the lath and plaster skin, which will not hold a heavy mirror on its own.

1 set · Drill bit set (2mm–4mm)

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AB-04Check for cables and pipes before you drill for realCables and pipes can run almost anywhere in a wall, and detectors miss deep cables, cables in metal conduit, and anything behind old metal lath mesh sometimes used under lime plaster. Treat the detector as a first check only, and still assume something could be there until you've drilled a small test hole and proved otherwise. Find your stopcock now, usually under the kitchen sink, and check it turns freely, so you can shut the water off fast if you hit a pipe. If you have any doubt at all about what's behind this spot, turn off the relevant circuit at the consumer unit before you drill.

AB-05Drill the fixing holes through the plaster into the timberStick a strip of masking tape over each mark first — this stops old lime plaster crumbling and cracking as the drill bites. Drill slowly on a low speed with no hammer action, starting with a small pilot bit, then opening out to the size needed for your screw. You need to go through roughly 15-25mm of lath and plaster and at least 40mm into solid timber, so use a screw or masonry-length bit long enough to reach that depth without falling short.

1 roll · Masking tape

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1 set · Drill bit set (4mm–6mm)

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AB-06Fit the right fixing for the weightFor a heavy mirror going into solid timber behind the lath, use a wood screw driven into the centre of the stud — no wall plug needed, the timber grips the thread directly. If your marked fixing point doesn't land on a stud, don't rely on the lath and plaster alone; fit a short timber batten across two studs first, screwed into both, then fix the mirror to the batten instead. If you later find your wall is actually plasterboard, dot-and-dab, or solid masonry rather than lath and plaster, the fixing changes: plasterboard between studs needs a toggle or hollow-wall anchor rated for the weight, dot-and-dab needs a fixing long enough to pass through the void and grip the masonry behind, solid brick or block needs the correct plug and drill size for that screw, and metal stud framing needs a proper metal-stud toggle fixing, never a wood screw or plastic plug, since it strips straight through thin steel.

2 each · Wood screws (60mm, No.8)

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1 each · Timber batten (25mm x 50mm, cut to length)

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AB-07Hang the mirror and check it's secureLift the mirror onto the fixings carefully, using two people if it's large or awkward. Check it's level with your spirit level and adjust the fixings slightly if needed. Give the frame a firm, gentle pull test from the bottom to confirm it's not shifting or pulling the fixing out of the plaster.

AB-08Clear up the plaster dustVacuum up loose plaster dust and crumbs from the floor and skirting before they get trodden in. Fold the dust sheet inward to trap any dust, then wipe down the wall below the mirror with a damp cloth. Put any spare fixings and offcuts away for next time.

1 each · Damp cloth

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