Gypsum lath should be applied with the long dimension perpendicular to which structural element?

Gypsum lath should be applied with the long dimension perpendicular to which structural element?

• A. Supports
• B. Joists
• C. Studs
• D. Beams

Answer: (A)

Gypsum lath acts as a rigid base for plaster, and its strength comes from how it’s fastened to the framing. The correct practice is to run the long dimension of the lath across the structural members, not parallel to them. When the long edge sits across supports, each edge of the sheet is anchored to a framing member, giving solid footing and preventing sagging. This orientation also helps the plaster grip the lath better and distributes movement across multiple supports, reducing the chance of cracks as the plaster dries and as the structure settles. If the long dimension runs along the supports, the sheet can bow between them and lose edge support, leading to cracks and a less stable plaster base. So orient the lath so its long direction is perpendicular to the underlying supports (across studs on walls, across joists on floors/ceilings).

Gypsum lath acts as a rigid base for plaster, and its strength comes from how it’s fastened to the framing. The correct practice is to run the long dimension of the lath across the structural members, not parallel to them. When the long edge sits across supports, each edge of the sheet is anchored to a framing member, giving solid footing and preventing sagging. This orientation also helps the plaster grip the lath better and distributes movement across multiple supports, reducing the chance of cracks as the plaster dries and as the structure settles. If the long dimension runs along the supports, the sheet can bow between them and lose edge support, leading to cracks and a less stable plaster base. So orient the lath so its long direction is perpendicular to the underlying supports (across studs on walls, across joists on floors/ceilings).