Residential Building Inspector B1Wall Construction and Wall CoveringsMedium
A homeowner is installing exterior stucco over a wood-frame wall. The plans specify a total stucco thickness of 7/8 inch. What is the minimum number of coats of stucco required for this application?
- AThree coats
- BTwo coats
- CFour coats
- DOne coat
Show answer & explanationAnswer & explanation
Correct answer: A. Three coats
According to IRC R703.7.3.1, stucco applied over wood frame construction, regardless of thickness, must be applied in not less than three coats: a scratch coat, a brown coat, and a finish coat.
Why the other options are wrong
- B. Two coats are sometimes used for thinner applications or specific systems, but not the minimum for traditional stucco over wood frame.
- C. Four coats are not typically required for standard stucco installations and would exceed the minimum specification.
- D. One coat stucco is typically for specific applications like direct application to masonry or concrete, not wood frame.
Stucco Coats (Wood Frame)
Stucco applied over wood frame construction requires a minimum of three distinct coats for proper adhesion and durability.
- First coat: Scratch coat (embeds lath).
- Second coat: Brown coat (builds thickness, provides level surface).
- Third coat: Finish coat (decorative and protective layer).
- Minimum 7/8 inch total thickness over wood frame.
Memory trick: Stucco coats are like a layered cake: first the scratch, then the brown, then the finish.