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IRC R403.1 — Footings (Residential Foundation Requirements)

Updated Mar 25, 2026
Minimum footing size for residential: 12-inch width for 1-story, 15-inch for 2-story, 18-inch for 3-story. Depth below frost line. Minimum 6 inches thick. Bearing on undisturbed soil or engineered fill.

IRC Table R403.1(1) prescribes minimum footing width based on number of stories and soil bearing capacity. For 2,000 psf soil: 1-story = 12 inches, 2-story = 15 inches, 3-story = 23 inches. For 3,000 psf soil: 1-story = 12 inches, 2-story = 12 inches, 3-story = 15 inches. For 4,000 psf soil: all 12 inches. Footing thickness: minimum 6 inches. Depth: must extend below frost line per local climate data (12 inches in South, 48+ inches in northern states). Concrete minimum: 2,500 psi for footings. Reinforcement: #4 bars minimum where required by Tables R403.1(2) and R403.1(3). Foundation walls: minimum 8-inch concrete or 8-inch CMU. Anchor bolts: 1/2-inch diameter, minimum 7 inches embedment, maximum 6 feet OC, within 12 inches of each end of sill plate. Alternatively: approved strap anchors. This is inspected at the foundation inspection — the most critical early hold point.

TAGS
ircfoundationfootingfrost-lineanchor-boltresidentialinspection
DETAILS
chapter
4 - Foundations
severity
prescriptive
code year
2024
code system
IRC
building types
["residential_single","townhouse"]
section number
R403.1
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