The first was the scratch coat which was a rough mixture of lime, sand, and water applied to the lath about 1/4 to 3/8″ thick and scratched with hand tools to provide a good bond for the second coat called the brown coat.

Traditionally plaster walls were applied in three successive coats. Rock lath, popular in the historical cusp years of of the 1940s and 1950s were 2×8 sheets of early drywall that were nailed to the studs and then the plaster was applied over top of it. There were other forms of lath popular in later years like metal lath which is still used today as a base for stucco applications and rock lath was a predecessor to drywall. This gap would allow the plaster to push through and form a “key” that once dry would hold the plaster securely to the wall. The plaster was applied over traditional wood lath which was nailed horizontally to the studs leaving small 1/4″ gaps between each strip of wood.

It could take up to a month (or even longer in cold climates) for a plaster wall to cure fully enough to allow for painting which slowed the construction process down. Plaster walls were applied wet by a skilled plasterer using a hawk and trowel. Understanding these walls will help you navigate things as diverse as the differences in hanging things on a plaster wall versus drywall, repair and patching techniques, and even WIFI issues and potential resolutions! Anatomy of Plaster Walls Whether it frustrates or inspires you it’s worth understanding what a plaster wall is and what some of the pros and cons are of this historical wall covering. Plaster was used for centuries as a wall covering and it wasn’t until the mid-1940s that it began to be replaced in favor of newer and faster option, drywall. Depending on your situation they can be both beautiful and annoying. Lath and plaster walls are a part of life in an old house.

Plaster walls plaster vs drywall