LA homes built before 1950 — Spanish revivals, Craftsman bungalows, mid-century apartments — almost universally have lath-and-plaster walls instead of drywall. That single difference makes TV mounting a different problem than in modern homes, and it's where most amateur installs fail. Here's exactly what the right approach looks like.
Why standard stud finders don't work
Lath-and-plaster construction uses thin wooden lath strips nailed to the studs, with plaster troweled over the lath. In some 1920s–1930s LA homes, that was reinforced with metal lath — a fine wire mesh embedded in the plaster.
Standard magnetic and radar-style stud finders read either the nails in the lath (every 6–10 inches) or the metal mesh (continuous, looks like studs everywhere). The result: you get false positives that don't correspond to actual studs, and a 60-pound TV mounted on lath alone will eventually pull out.
The right tools for the job
Two stud finders work reliably on lath-and-plaster. The Franklin ProSensor 710+ uses a multi-sensor array that reads past the lath layer to find the actual stud edges. The Walabot DIY Plus uses radar that can be calibrated past lath density. Either tool, used with a known-stud reference (a doorframe edge, an outlet box screw), will give you accurate stud locations.
Tape the stud locations carefully and verify with a second tool or a small pilot bore before committing to lag bolts. The pilot bore is the final check — if the bit feels solid and bites, you've found wood; if it feels hollow or grindy, you're in lath only and need to move.
The right hardware for the load
For TVs under 55 inches mounted with a fixed bracket, lag bolts directly into stud are sufficient. Use 5/16-inch x 3-inch lag bolts with washers, and predrill with a 7/32-inch bit so you don't crack the plaster around the entry hole.
For TVs 55–75 inches with a tilt or full-motion arm, the dynamic load doubles when the arm extends. Use 3/8-inch x 3-inch lag bolts and confirm two studs minimum behind the bracket.
For TVs over 75 inches or above-fireplace mounts, we install a hardwood mounting plate (a piece of 1/2-inch plywood) lag-bolted to multiple studs first, then mount the TV bracket to the plywood. The plywood spreads the load across more studs and gives full bracket-position flexibility without trying to align directly to studs.
Cable concealment in lath-and-plaster
Routing HDMI and power cables behind plaster requires a specific approach. Cut a small drywall-style access opening (or use a low-voltage old-work bracket) below the TV at outlet height. Use a fish tape or magnet retrieval kit to pull the cables vertically through the wall cavity. The lath layer can catch the fish tape; using a strong-magnet retrieval system from below works better than blind fishing in older walls.
Cable concealment in lath-and-plaster runs slightly more than drywall installs because of the extra time, but the cost is still typically $185–$285 for clean in-wall routing.