What is the role of a brown coat in a multi-coat plaster system?

• A. To build thickness, increase strength, and provide a smooth surface for the finish coat
• B. To add decorative texture
• C. To seal moisture
• D. To color-match the plaster

Answer: (A)

In a traditional multi-coat plaster system, the brown coat is the thick, structural layer that builds the wall thickness and adds most of the system’s strength. After the scratch coat creates a key and base, the brown coat is applied to reach the required thickness and to harden into a solid substrate. It is then floated and leveled to produce a true, smooth plane that the final finish coat can bond to and decorate. It isn’t meant for decorative effects, moisture sealing, or color; those roles belong to the finish coat or other system components. The finish coat is what provides texture and color, while the brown coat provides the solid, even base.