The brown coat is applied over the scratch coat to prepare the plaster base for the finish coat application.
The brown coat is the second coat of stucco applied to the wall. The brown coat creates the level surface that’s desirable for the finish coat. Mix the brown coat, following the manufacturer’s instructions. Ensure that the proper proportions of cement, sand, and water are used in the mix. Generally, the brown coat requires slightly more sand than the scratch coat in order to make it weaker. Let the mix sit for 20 minutes before remixing it for application. Make sure to dampen the scratch coat before applying the brown coat.
Apply the brown coat to the wall at a uniform thickness of 1/4-inch to 3/8-inch, except at architectural details, where it may be thicker. The brown coat provides architectural character, such as slopes and edges. After it’s applied, screed the brown coat, and create a smooth, consistent surface with an 8′ level or straight edge.
Screeding causes stucco to drop off the wall onto horizontal surfaces, such as manufactured stone or brick, that may already be in place. Clean excess stucco from horizontal surfaces immediately after screeding. Hydrate the brown coat in the same manner as the scratch coat.
Scratch coats are mixed at 1 part cement to 2-1/4 to 4 parts sand, brown coats are mixed at 1 part cement to 3 to 5 parts sand, and finish coats are 1 part cement to 1-1/2 to 3 parts sand.
