Answer :

The 3 coats of plaster used over expanded metal lath are:

  • Scratch coat- The first plaster coat, is scratched to create a bond for a second coat.
  • Brown coat- The second plaster coat, is applied after the scratch coat and used to level the surface. (about 1/4 ")
  • Finish coat- The third and final application of plaster gives the surface its desired texture and final leveling. (1/8 "thick)

What is plaster?

A paste-like cementitious substance that is applied to lath or brickwork to create a completed surface and is typically based on gypsum or Portland cement applied either manually or by a machine.

What is lath?

A foundational substance to which plaster is put. Most laths used nowadays are either prefabricated gypsum boards or expanded metal.

What is the purpose of metal lath?

The stucco cementitious membrane is embedded and fastened to the building's structural components using metal lath as a platform. Without the lath, applying stucco to open-frame or sheathed construction would be difficult or impossible.

Learn more about lath: https://brainly.com/question/8236547

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Final answer:

There are typically three coats of plaster used over expanded metal lath: the scratch coat, which keys into the lath; the brown coat, which provides strength and levels the surface; and the finish coat, which is the final aesthetic layer.

Explanation:

When applying plaster over expanded metal lath, there are typically three coats used, each serving a specific purpose:

  1. Scratch Coat: The first layer applied directly to the metal lath. Its primary role is to key into the lath to provide a strong mechanical bond. It is rough and not smoothed out because as it dries, the scratches will help the next layer, the brown coat, adhere better.
  2. Brown Coat: This is the second layer applied over the scratch coat. It helps to even out the plaster base for a smoother surface and provides additional strength and stability for the plaster wall. It also helps to level the surface and prepare it for the final coat.
  3. Finish Coat: The final layer of plaster, which is smooth and provides the appearance of the wall. It is meant for aesthetic purposes, as it can be colored or textured according to the desired final appearance.

Each coat plays an essential role in creating a durable and visually appealing plaster finish over metal lath.

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