What is the difference between 'lath and plaster' and 'plaster over gypsum board'?

What is the difference between 'lath and plaster' and 'plaster over gypsum board'?

• A. Lath and plaster uses gypsum board backing; plaster over gypsum board uses lath backing.
• B. Lath and plaster uses lath backing; plaster over gypsum board uses gypsum board backing with veneer plaster.
• C. Both methods use gypsum board backing with veneer plaster.
• D. They are the same technique with identical backing.

Answer: (B)

The difference comes down to the backing and how thick the plaster coating is. In traditional lath and plaster, plaster is applied over a framework of lath (wood or metal) that provides a rough surface for the plaster to key into, and the plaster is built up in multiple coats to create a thick, durable wall. In plaster over gypsum board, the backing is gypsum board (sheetrock) and a veneer plaster coat is applied on top as a thin final skin, resulting in a lighter system that relies on the gypsum board as the substrate. That’s why the statement that matches reality is: lath and plaster uses lath backing; plaster over gypsum board uses gypsum board backing with veneer plaster. The other descriptions mix up the backing or imply both use the same approach.

The difference comes down to the backing and how thick the plaster coating is. In traditional lath and plaster, plaster is applied over a framework of lath (wood or metal) that provides a rough surface for the plaster to key into, and the plaster is built up in multiple coats to create a thick, durable wall. In plaster over gypsum board, the backing is gypsum board (sheetrock) and a veneer plaster coat is applied on top as a thin final skin, resulting in a lighter system that relies on the gypsum board as the substrate.

That’s why the statement that matches reality is: lath and plaster uses lath backing; plaster over gypsum board uses gypsum board backing with veneer plaster. The other descriptions mix up the backing or imply both use the same approach.