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Lath and plaster

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Lath and plaster is a way to finish indoor walls and ceilings.

Lath
Lath

This method makes a solid surface for a room. It works by using many small pieces to build a large wall. Builders often use this for dividing walls inside a house. It is a very old way of building. It actually comes from an even older method called wattle and daub. Even though we use new things now, this method is still very important to know about.

Lathwork and plaster
Lathwork and plaster

To start, builders nail thin strips to the wall frame. These strips are called laths. They can be made of wood, metal, or split boards.

Lath
Lath

The laths are nailed horizontally across the studs. In the United Kingdom, builders often used split hardwood laths. In North America, they usually used sawn wood. There are small gaps between each strip of lath. Next, a worker uses a wooden board to spread wet plaster. They drag the board upward over the wall. This forces the plaster into the gaps. The plaster curls behind the laths to form shapes called keys. These keys hold the plaster in place. Sometimes, horsehair is added to the plaster to make it stronger.

Building with lath and plaster has changed over many years.

Lathwork and plaster
Lathwork and plaster

In the United States and Canada, people used wood lath for a long time. They used it well into the second half of the 19th century. As people moved west, they used split beam lath because saw mills were not always nearby. By the end of the 19th century, metal lath became more common. Around 1900, a new kind called rock lath began to be used. This was an early form of drywall. By the late 1930s, rock lath was the main way to do residential plastering. In the United Kingdom, plasterboard became popular after the 1930s.

There are many specific details about how these materials look and work.

Lath
Lath

Wood laths are usually thin and narrow. Metal lath can come in large sheets. Rock lath sheets are often four feet long. This length is special because it spans three studs perfectly. When applying plaster, a worker might apply three different layers. The first layer is the base coat. The second layer is a rough, sandy layer called a brown coat. The final layer is a smooth, white finish coat. Once the plaster is completely dry, the wall is ready for paint. This careful process creates a very thick and heavy wall.

Modern builders often use drywall instead of lath and plaster today. Drywall is faster and costs less money to install. However, lath and plaster has some special advantages. It is much better at blocking sound from traveling through walls. It is also very good at stopping fire from spreading.

Lathwork and plaster
Lathwork and plaster

This helps protect the wooden floors in old buildings. Another great thing is that lath and plaster is flexible. It can be used to make rounded or curved walls. Modern drywall is not flexible enough to make tight curves like this. This makes the old way perfect for unusual or beautiful shapes.

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