Section 1803: Geotechnical investigations required for: buildings >1 story, retaining >4ft, piles/piers, structures on potentially problematic soils. Report includes: soil classification, bearing capacity, settlement analysis, lateral pressures, groundwater. Section 1804: Excavation/grading/fills — fill placement in max 12in lifts, compacted per geotech recommendations. Section 1806: Foundation design: presumptive bearing values (Table 1806.2): crystalline bedrock 12,000 psf, sedimentary 4,000, sandy gravel 3,000, sand 2,000, clay 1,500. Or per geotech report. Section 1808: Footings — depth below frost line, min 12in below adjacent grade. On stable undisturbed soil or compacted fill. Section 1810: Deep foundations — piles: driven, drilled, helical, micropile. Minimum 2 test piles per building. Load test per ASTM D1143. Section 1807: Foundation walls — damp-proofing required, waterproofing for habitable below-grade spaces.