Picking interior materials isn't just an aesthetics exercise. Every wall covering, ceiling tile, and floor finish carries fire performance ratings, acoustic properties, indoor air quality implications, and cost consequences that directly shape whether a building meets code, program, and budget. The IBC classifies interior wall and ceiling finishes into Classes A, B, and C based on flame spread and smoke-developed indexes tested per ASTM E 84. Those classifications vary by occupancy group and location within the building; exit enclosures demand higher-performing finishes than general rooms. Beyond fire, architects must evaluate acoustic performance (NRC and CAC ratings for ceiling systems), material emissions (low-VOC and formaldehyde-free requirements), durability, and sustainability credentials. For PPD Objective 3.4, NCARB expects you to select materials and assemblies that satisfy programmatic, budgetary, and regulatory requirements simultaneously, then evaluate how those choices ripple through the total building design. That means analyzing trade-offs: a suspended acoustical ceiling tile system rated for high CAC might solve noise transmission between floors but conflict with the mechanical engineer's ductwork routing. A Class A wall finish in a Group A assembly occupancy costs more than a Class C finish permitted in a small office. This topic walks through the fire classification system, acoustic performance metrics, indoor environmental quality standards, and the evaluative framework you need to make defensible material selections on exam day.