Site Work, Foundations, and Concrete
What this domain tests
Site preparation, footing and foundation construction, and concrete placement are where Michigan's climate does the most damage. Items test grade and drainage, frost-depth footings, reinforcement and anchor placement, air entrainment, and cold-weather practice.
Core rules
- Grade: finish grade slopes away from the foundation, about 6 in. within the first 10 ft. Strip topsoil before footing excavation.
- Footings: minimum 6 in. thick, sized from the load and soil-bearing values, bearing on undisturbed soil below frost depth.
- Foundation walls: minimum 2,500 psi concrete; anchor bolts at least 1/2 in. diameter, spaced no more than 6 ft on center and within 12 in. of wall ends and corners.
- Drainage: footing drain tile, washed gravel, filter fabric, and damp-proofing or waterproofing before backfill. Backfill after the foundation inspection, in compacted lifts.
- Air entrainment: Michigan freeze-thaw exposure calls for roughly 5–7% entrained air, with a low water-cement ratio - not extra cement to compensate.
- Cold weather: protect fresh concrete once air temperature approaches 40°F and falling; maintain curing temperature and never place on frozen subgrade.
Worked example
A 24 ft x 30 ft garage slab at 4 in. thick: 720 sq ft x (4 ÷ 12) ft = 240 cu ft, and 240 ÷ 27 = 8.9 cu yd. Add 5% waste for grade variation and spillage: 8.9 x 1.05 = 9.3, so order 9.5 cu yd. Ordering 8.9 cu yd leaves the last third of the slab short.
Traps that cost marks
Using slab thickness in inches without converting to feet; backfilling before the foundation inspection; assuming 3,000 psi mix makes air entrainment unnecessary; setting anchor bolts after the pour; sloping grade toward the house to "drain the yard."