Presumptive Soil Bearing Capacity Chart — IBC Table 1806.2 Values
IBC Table 1806.2 presumptive load-bearing values: 1,500–12,000 psf vertical pressure by soil and rock class with kPa conversions and lateral values.
Updated August 18, 2026
When no geotechnical report exists, the International Building Code lets prescriptive foundation design fall back on Table 1806.2: five broad material classes, each with a presumptive vertical bearing pressure, a lateral bearing value per foot of depth, and a lateral sliding resistance. The classes are keyed to the Unified Soil Classification System symbols, so a soil identified as SM (silty sand) reads 2,000 psf and a CL (lean clay) reads 1,500 psf. These are deliberately conservative floor values for allowable stress design — a site investigation will almost always justify more.
The presumption has hard limits. Mud, organic silt, organic clays, peat, and unprepared fill get no presumptive capacity at all — Section 1806.2 requires substantiating data before assigning them any value. And where a soil is questionable, expansive, or the structure is outside prescriptive scope, the building official can require the geotechnical investigation of Section 1803 regardless. Treat this chart as the code’s fallback for simple foundations, not as a substitute for knowing what is actually under the footing.
IBC Table 1806.2 — Presumptive Load-Bearing Values
| Class of materials (USCS symbols) | Vertical pressure (psf) | Vertical pressure (kPa) | Lateral bearing (psf/ft below grade) | Lateral sliding resistance |
|---|---|---|---|---|
| Crystalline bedrock | 12,000 | 575 | 1,200 | Friction coefficient 0.70 |
| Sedimentary and foliated rock | 4,000 | 192 | 400 | Friction coefficient 0.35 |
| Sandy gravel and/or gravel (GW, GP) | 3,000 | 144 | 200 | Friction coefficient 0.35 |
| Sand, silty sand, clayey sand, silty gravel, clayey gravel (SW, SP, SM, SC, GM, GC) | 2,000 | 96 | 150 | Friction coefficient 0.25 |
| Clay, sandy clay, silty clay, clayey silt, silt, sandy silt (CL, ML, MH, CH) | 1,500 | 72 | 100 | Cohesion 130 psf |
PRESUMPTIVE VALUES FOR PRESCRIPTIVE DESIGN ONLY — a site-specific geotechnical investigation governs whenever one exists or is required (IBC §1803). kPa computed at 0.047880 kPa/psf, rounded to whole kPa. Friction coefficients multiply the dead load; the 130 psf cohesion multiplies the contact area (limited by §1806.3.2). Mud, organic silt, organic clay, peat and unprepared fill have NO presumptive capacity. Values are ASD-basis (§1806.1) and may be increased by one-third under the alternative load combinations of §1605.3.2 that include wind or earthquake.
Sources & Further Reading
- International Building Code, Table 1806.2 — verified against UpCodes reproductions of IBC 2021 and IBC 2018 (unamended state adoptions) and an independent industry reproduction of IBC 2012; identical across all three
- IBC §1806.1–1806.3.2 body text for the ASD basis, one-third increase, mud/organic exclusion, and sliding limits
Frequently Asked Questions
Can I design a footing straight from these values?
Only within the prescriptive path: light, conventional construction where the code allows presumptive values and the soil class is confidently identified. The values are conservative floors for allowable stress design. Any geotechnical report supersedes them, and the building official can demand one for questionable soils, expansive clays, or anything structurally unusual.
Why is the clay row only 1,500 psf when clays can test much stronger?
Because the row must cover everything from stiff CL to soft, moisture-sensitive CH with no site data. A presumptive table has to be safe for the worst plausible member of the class, so it gives away most of the strength a real investigation would recover — on decent clay a geotechnical report commonly justifies 2–3 times this value.
What do I use for fill, peat, or organic soils?
Nothing, presumptively. IBC 1806.2 explicitly denies mud, organic silt, organic clays, peat, and unprepared fill any presumptive load-bearing capacity — you must submit data substantiating a value, which in practice means a geotechnical investigation or engineered, compaction-tested fill placed under Section 1804.
How do the lateral columns work?
Lateral bearing accrues per foot of embedment below natural grade — a pole embedded 4 ft in sandy gravel may resist 4 × 200 = 800 psf at the bottom of the embedment. Sliding uses either a friction coefficient times the dead load (granular soils and rock) or, for the clay class, 130 psf of cohesion times the contact area, capped by Section 1806.3.2 at half the dead load.
Try the Calculators
Presumptive Soil Bearing Capacity Chart — IBC Table 1806.2 Values — reuven.tools/reference/presumptive-bearing-values — verified against: International Building Code, Table 1806.2 — verified against UpCodes reproductions of IBC 2021 and IBC 2018 (unamended state adoptions) and an independent industry reproduction of IBC 2012; identical across all three; IBC §1806.1–1806.3.2 body text for the ASD basis, one-third increase, mud/organic exclusion, and sliding limits