A spread-footing foundation case study for a two-story wood-frame residence on 2,500 psf soil — a full roof-to-footing load takedown, a strip footing sized by IRC prescriptive minimum instead of the bearing calculation, and an isolated garage-header pad footing worked from a real point load.
The project brief: a 28 ft x 44 ft two-story residence needs a shallow spread-footing foundation on moderate, ordinary soil — no basement, slab-on-grade first floor, roof and second-floor loads carried down exterior stud walls to a continuous perimeter strip footing, plus isolated pad footings under porch and garage-opening posts. It's the most common foundation problem a civil/structural engineer sees, and the real skill it tests is running a complete load takedown and correctly recognizing when a code-prescriptive minimum, not the calculation, governs the final dimension.
This module walks the whole design the way a real foundation engineer would: a per-linear-foot load takedown from roof through wall to footing, a strip footing bearing check that gets overridden by IRC Table R403.1's prescriptive minimum width, a separate frost-depth embedment check, and a fully worked isolated pad footing under a garage header post. The full worked numbers, complete bill of materials, and finished design reasoning are part of the unlocked module below.