BD-05Fit a plywood backing board across the studsA barn door track and door are heavy, and old lath and plaster alone will not hold the load — you need a solid timber backing board screwed into whatever is behind the plaster. Cut an 18mm exterior-grade plywood board the length of your track run and 150-200mm deep, then hold it against your level line and mark through it onto the wall. For timber studs, screw through the board and plaster straight into the centre of each stud with 4x60mm wood screws, at least one fixing per stud. For metal studs found in a refurbished wall, do not use wood screws or plain plastic plugs — they strip straight through 0.5mm steel; use self-drilling metal-stud screws, but know a metal stud alone won't carry a barn door, so fit a timber noggin between the studs first or fix through to solid masonry behind if there is any. For solid brick or block found behind the lath, drill a 6-7mm hole through the board and plaster, insert masonry wall plugs, and use 6x75mm screws so they bite at least 40mm into the masonry. If you discover the wall is actually dot-and-dab plasterboard on masonry rather than true lath and plaster, the adhesive dabs won't hold the weight either — use 75-100mm screws long enough to pass through the board, the plasterboard and the dab void, and bite at least 40mm into the solid wall behind. Pack any gaps behind the board with thin timber shims so it sits flat and doesn't crack the old plaster as you tighten the screws.