"Plaster and lath" refers to an older style of interior wall that uses wooden lath attached directly to the studs; the lath is then embedded with plaster.
The plaster dries to form a hard, smooth surface suitable for finishing with paint or wallpaper. Plaster and lath is rarely used now, except to repair existing plaster and lath walls.
The Original Way To Finish a Wall--Long Before Drywall
A majority of homes built prior to World War II used plaster and lath construction. After the War, drywall (i.e., plasterboard or wallboard), came into vogue and supplanted plaster and lath as the main mode of interior wall construction.
This style precedes the use of drywall as a means of covering up studs on the interior of a house. Essentially, drywall acts the same way as plaster, since both are mineral products.
The difference is that the "plaster work" has already been done ahead of time, in a factory (thus, the word "dry" in drywall). Since drywall is stiff, lath is not necessary and it is nailed directly onto the studs.
Plaster-and-Lath vs. Drywall
Plaster and lath walls are usually as thick or thicker than most drywall. While cracking plaster is a common feature of older homes, as long as the material is intact, there is no reason to replace it with drywall.
However, if you are demolishing your plaster walls, for most homes it is recommended that you replace them with drywall. Drywall is exceedingly easier for DIY homeowners to work with. The only exception would be if you are restoring a historic home.
Plaster and lath is a process that takes several days.
- Lath Built: A substrate in the form of a grid of lath is nailed perpendicular to the open house studs roughly a finger-width apart from each other. Lath is rough, unfinished wood about 1" to 2" wide and about 3' to 8' long. Sometimes, in lieu of wooden lath, this base surface is a metal grid.
- Plaster Stage: A thick layer of wet plaster is hand-troweled onto the lath.
- Keys Develop: Globs of plaster are pushed out of the back side of the lath and dry, forming a myriad of secure grips for the rest of the plaster. These dried globs are called "keys," and make demolition of plaster down the road much harder.
- Finish: The finish surface, such as paint or wallpaper, is applied.
Although few houses are built from scratch with the lath and plaster technique, countless houses remain with this type of building material.
Homeowners can repair plaster walls by themselves quite easily. Also, companies which specialize in finishing drywall may be able to repair plaster walls, as well. Of course, urban areas that have a large quantity of older houses may have tradesmen who specialize only in plaster application and repairs.