Building Systems, Construction, and Interior Detailing
This domain tests whether your drawings can actually be built: how structure, plumbing, mechanical, and electrical services intersect with ceiling heights, cabinetry, and finishes, and whether your sections and enlarged details communicate the assembly.
Core rules
- Know the drawing set: floor plans, reflected ceiling plan, interior elevations, sections, enlarged details, finish plans, and schedules for doors, windows, finishes, and fixtures.
- Coordinate services early: plumbing stacks want to align vertically (bath over bath); a 3 in drain needs deep framing or a soffit; HVAC trunks need 8-12 in plus insulation; a flush 9 ft ceiling under 12 in joists usually cannot carry a duct.
- Dimension to finished faces, not framing - finish floor, finished wall. Show blocking for grab bars, TV mounts, and heavy shelving.
- Ceiling math: floor-to-floor minus structure minus services minus furring equals clear height.
Worked example
A 10 ft floor-to-floor with 12 in joists and 3/4 in subfloor leaves about 107-1/4 in below joist. A 10 in round duct plus 1 in insulation plus 5/8 in gypsum consumes 11-5/8 in, so the soffit bottom lands at 95-5/8 in (7 ft 11-5/8 in) - above the 7 ft habitable minimum and above the 6 ft 8 in door head. If the client insists on a flush 9 ft ceiling, the duct must move to a chase or run between joists with a transfer, because 108 in of clear height leaves only 12 in for everything.
Traps
- Detailing to nominal lumber and forgetting a 2x4 is 1-1/2 x 3-1/2 in.
- Ignoring build-up: tile, backer board, and thinset add 3/4-1 in to a wall and shift a counter.
- Skipping return-air paths when adding a door - use a 1 in undercut or transfer grille.
- Specifying an appliance before confirming the rough opening and door swing.