Lath and Plaster

Lath and Plaster – a common method of finishing interior wall and ceiling framing prior to the late 1950s after which lath and plaster was largely replaced with drywall.

lath and plaster wall seen from the back with brown coat oozing through

The lath and plaster process consists of tacking thin strips of wood lath over the entire wall or ceiling framing members with approximately 3/8 inch gaps between the strips.  Lime or gypsum based putty is then applied in three coats.  The first, called the scratch coat is applied about 3/8 inch thick and is also forced between the gaps in the laths forming “keys” that lock into the gaps and ensure a solid bond.  The “brown coat comes next.  It is also approximately 3/8 inch thick and is troweled into a semi-smooth uniform surface. A final 1/8 inch thick “white coat” is applied which completes the process leaving a uniform, smooth textured surface that is ready to paint.