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What is Lath and Plaster?

Updated: Sep 11, 2020

Lath and plaster were the materials used for interior walls in older buildings and homes. Today, new builds no longer use lath and plaster however with restoration and historic preservation lath and plaster remain.

Lath, also known as slats, refers to the narrow wood that is installed between the vertical support posts of a soon-to-be wall. The word, although traditionally known as the above, has now become synonymous for any backing for plaster.

Two examples of lath and plaster at The O'Rourke Building; the team will repair these spots, maintaining as much of the original parts of the building as possible.

Plaster is the paste-like component that is smeared over the lath sealing the spaces and securing the robustness of the wall, and is more appealing to the eyes. This material is typically made out of sand, lime, gypsum and water. Its application goes on wet and dries to create a sturdy solid.

Lath and plaster was not the first of its kind. As long ago as 6,000 years, structures were built using a technique known as wattle and daub. Wattle is the strips of wood woven into a grid between support posts. Daub refers to the act of applying material to cover the wattle. This substance was commonly made of clay, sand, straw and/or animal excrement.

From left to right: A close up of wattle and daub; two structures built using wattle and daub

With time, this rudimentary technique became refined. But wattle and daub established a foundational piece in the construction of buildings and homes. The process of the current day remains nearly identical; once the lath is in place, plaster is spread across the surface to cover the space and create a wall.

Even older than wattle and daub is plaster. The word plaster comes from the Greek work "to daub on." (Everything comes full circle.) Plaster and plastering can be found in ancient architecture from the Egyptian Pyramids to Ancient Greece. It was also the canvas for Michael Angelo's Sistine Chapel ceiling. Not only was plaster used for covering interior walls, it was also used for patchwork and molding into decorative elements. Today these earliest plasters remain intact and as strong as ever.

Right: Ancient Egyptian art on plaster

Left: A Decorative head from Ancient Greece made of plaster

Now that drywall has taken the place of lath and plaster the need for repairs are few and far between. However, with projects such as The O'Rourke in Butte, Montana, maintaining and thus, repairing the lath and plaster will be done to maintain as many original elements of the building as possible. It is also more time and budget efficient to fix small spots or larger gaps than to replace an entire wall.

The methods of construction continue to advance. As new materials and technologies become available the trade grows and moves away from older processes. Lath and plaster will eventually disappear as older buildings are torn away for new much like its predecessors. At the core of it, the overall reason for plastering, wattle and daub, lath and plaster remain; a basic need for shelter and stability.

Lath and plaster from The O'Rourke Building.

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