Room 31B is the western portion of Room 31W. it measures 2.9 x 2.5. Twelve strata were identified in 31B including post-occupational units, roof-fall, and a floor. The most recent stratum, the floor complex, revealed evidence of the fire that destroyed Salmon Pueblo. Five features were associated with Room 31B, including a San Juan period wall dividing 31B from 31A.