How is substrate moisture content considered in plastering?

How is substrate moisture content considered in plastering?

• A. It has no effect
• B. It only affects color
• C. It affects bonding and curing; must be within recommended range
• D. It only affects drying time

Answer: (C)

Substrate moisture content is a deciding factor for how well plaster bonds and cures. The moisture level at the surface controls suction—the tendency of the substrate to draw water from the plaster. If the substrate is too dry, it will suck water out of the plaster quickly, causing rapid stiffening, poor adhesion, and a fragile bond with the surface. If the substrate is too wet, suction is reduced, so the plaster may not grip properly, can slump, and curing can be uneven, leading to weak sections or surface defects. That’s why you must keep the substrate moisture within the range recommended by the plaster product and project specs. Testing the surface and adjusting with controlled dampening or priming helps ensure consistent suction, proper bonding, and a sound cure.

Substrate moisture content is a deciding factor for how well plaster bonds and cures. The moisture level at the surface controls suction—the tendency of the substrate to draw water from the plaster. If the substrate is too dry, it will suck water out of the plaster quickly, causing rapid stiffening, poor adhesion, and a fragile bond with the surface. If the substrate is too wet, suction is reduced, so the plaster may not grip properly, can slump, and curing can be uneven, leading to weak sections or surface defects. That’s why you must keep the substrate moisture within the range recommended by the plaster product and project specs. Testing the surface and adjusting with controlled dampening or priming helps ensure consistent suction, proper bonding, and a sound cure.