GuidelineRecommended
Presumptive soil-bearing value default: 1500-2000 psf for sand/gravel; verify with site investigation for higher
HUD RSDG §4.5Description
Without a site-specific soil investigation, residential designers may use IRC R401.4.1 presumptive values: 1500 psf for clay/silt, 2000 psf for sand/gravel mixes, 3000 psf for sandy gravel, 4000 psf for sedimentary rock. Higher values require geotechnical investigation.
Why this exists
Foundation footing sizing follows directly from bearing capacity. The IRC's presumptive values are conservative; actual soils often support higher loads but require investigation to claim them.
Measurements
| Property | Operator | Value | Unit | Note |
|---|---|---|---|---|
claySilt | exact | 1500 | psf | Presumptive bearing for clay/silt |
sandGravel | exact | 2000 | psf | Presumptive bearing for sand/gravel |
sandyGravel | exact | 3000 | psf | Presumptive bearing for sandy gravel |
sedimentaryRock | exact | 4000 | psf | Presumptive bearing for sedimentary rock |
Categories
Structure
Source
HUD (US Department of Housing and Urban Development)no manifest entry
Residential Structural Design Guide, Second Edition (2nd ed)
Section: Chapter 4, §4.5
Published 2000-01-01 · last verified 2026-05-10
Solver enforcement
Browsable only — the solver does not currently enforce this directive (no spec-level data to check against). This entry exists so the architect personas can cite it in conversation and the user can read what the rule says.
Related directives
- Continuous load path from roof to foundation · HUD RSDG §2.4
- Residential structural reliability targets 1-in-100 to 1-in-1000 annual probability of failure · HUD RSDG §2.5
- Residential floor live load: 40 psf minimum (30 psf sleeping rooms) · HUD RSDG §3.4
- Wind load design uses ASCE 7 basic wind speed for the locality · HUD RSDG §3.6
- Ground snow load for Virginia: 25 psf eastern, up to 40 psf western mountains · HUD RSDG §3.7
Last reviewed 2026-05-10.