IRC Section R301 establishes the design basis for all one- and two-family dwellings and townhouses. Key design values determined by jurisdiction: ground snow load (psf), wind speed (mph — 3-second gust per ASCE 7), seismic design category (A through E), weathering probability for concrete (severe/moderate/negligible), frost line depth (inches), termite probability, winter design temperature, flood hazard. Live loads per R301.5: floors 40 psf, sleeping rooms 30 psf, attics with storage 20 psf, attics without storage 10 psf, decks 40 psf, guardrails/handrails 200 lb concentrated. Dead loads assumed: 10 psf for floors, 10 psf for walls, 10 psf for roofs (plus snow). These values feed directly into the prescriptive tables in IRC Chapters 4-8 for foundation, floor, wall, and roof sizing.