Interior Construction and Finishes
Interior Construction and Finishes
This LICT-Interior domain tests the built interior: cold-formed steel framing, gypsum board assemblies, ceilings, substrates, millwork, and finish flooring. Questions often ask you to compare an installed condition with a standard, a listing, or the manufacturer's written instructions, then decide whether to accept, reject, or require correction.
Core rules
- Cold-formed steel framing follows ASTM C754: studs at 16 or 24 in. on center, track anchored per design, and deflection track where structural movement occurs. Do not cut stud flanges to make services fit.
- Gypsum board application follows ASTM C840 and GA-216. Stagger joints on opposite sides, keep fasteners just below the paper surface, and use the board type the assembly requires: Type X for fire resistance, moisture-resistant board in damp areas, and cement backer board where direct water contact occurs.
- A fire-rated assembly is a tested system, not just a board type. The UL or GA listing controls board thickness, layers, fastener type and spacing, stud spacing, and joint treatment.
- Ceiling grid and hangers follow the manufacturer's layout and the seismic design where required; main runners, cross tees, and perimeter attachment must match the approved submittal.
Worked example
A corridor wall is specified as a 1-hour assembly with 5/8 in. Type X gypsum board on 16 in. o.c. steel studs. The crew installs the correct board but uses 1 in. screws at 16 in. o.c. in the field; the approved listing shows 12 in. o.c. at board edges and in the field. The correct decision is to reject the work. ASTM C840 gives general installation rules, but the listed fire-resistance design is more restrictive and governs. The fix is to add screws at the listed spacing without overdriving them.
Traps
- Treating Type X as a substitute for moisture-resistant or abuse-resistant board.
- Overdriven screws that break the paper face and reduce holding power.
- Omitting control or expansion joints at large openings.
- Using generic sealant instead of the listed firestop system at penetrations.