Floor, Wall, and Ceiling Framing
Floor systems
Platform framing proceeds from the sill plate (drilled for anchor bolts) to the band or rim joist, then floor joists, bridging or blocking, and the subfloor. Joist size and spacing come from span tables - never guess. Boring and notching rules are heavily tested: a notch may not exceed one-quarter of the joist depth, may not be located in the middle third of the span, and a hole may not exceed one-third of the depth and must stay at least 2 in from the top and bottom edges.
Wall and ceiling framing
Walls are laid out on the subfloor with studs at 16 in or 24 in on center, measured center to center, starting from a corner or from the end of the wall. Learn the parts of an opening: king stud, trimmer (jack) stud, header, cripple stud, rough sill. A double top plate ties walls together at corners and partitions, and fire blocking is required at specified intervals. Ceiling joists tie opposing rafters and resist outward thrust.
Worked example: a 20 ft wall at 16 in o.c. is 240 in ÷ 16 = 15 spaces, plus one stud = 16 studs, then add studs for corners, openings, and intersections.
Traps: measuring spacing from stud edges instead of centers; forgetting the extra stud; forgetting that stud length equals wall height minus the plate thicknesses.