CBC · California Building Code

How close can fills/surcharges and slopes be to a building/foundation?

You generally cannot place fill or surcharge next to a building unless the structure can resist the added loads (or you protect/underpin the footings); small landscape fills ≤1 ft by walk‑behind equipment are excepted. Buildings adjacent to slopes steeper than 1:3 must meet the setback/clearance rules in § 1808.7 (very steep slopes have a specific 45° toe measurement). For any non‑routine fills or steep slopes expect to provide a geotechnical report and engineered protections.

Ask a question free See coverage

Last reviewed: July 5, 2026

What the code requires — 2-4 sentences

You may not place fill or other surcharge loads adjacent to a building or structure unless the building is capable of resisting the additional loads (and existing footings affected by nearby excavation are underpinned or otherwise protected) — § 1808.3.2. For buildings on or adjacent to slopes steeper than 1 vertical in 3 horizontal (33.3% slope), foundations and clearance from the slope must meet the criteria in § 1808.7 and § 1808.7.1 (including specific measurement rules for very steep slopes and allowance for alternate setbacks with building‑official approval).

Requirements in detail

General rule for fills / surcharges

  • Fill or surcharge loads shall not be placed adjacent to any building unless the building is capable of withstanding the additional loads. Existing footings or foundations that could be affected by excavation shall be underpinned or otherwise protected against settlement and lateral/vertical movement. This is the controlling requirement in § 1808.3.2.
  • There is a limited exception for minor landscaping grading: grading performed with walk‑behind equipment or grade increases not more than 1 foot from original design grade (or where approved by the building official) is permitted without meeting the full § 1808.3.2 requirements.

Foundations near slopes (when slope > 1:3)

  • § 1808.7 applies where buildings are on or adjacent to slopes steeper than 1 vertical in 3 horizontal (33.3%): foundations must meet the clearance/setback and support requirements of §§ 1808.7.1–1808.7.5. The code assumes those distances provide protection from slope drainage, erosion and shallow failures unless an alternate setback is approved.
  • For slopes steeper than 1 vertical in 1 horizontal (100% slope) there is a specific geometric assumption for the location of the slope toe: assume the toe is at the intersection of a horizontal plane drawn from the top of the foundation and a plane tangent to the slope at 45° to the horizontal. If a retaining wall is at the toe, measure slope height from the top of the wall. See § 1808.7.1.
  • Foundations on or adjacent to descending slope surfaces must be founded in firm material, with embedment and setback sufficient to avoid detrimental settlement; where slopes are >1:1 the required setback is measured from an imaginary 45° plane projected upward from the toe. See § 1808.7.2.
  • Pools have a special rule: the setback between pools and slopes equals one‑half the building footing setback required by § 1808.7, and pool walls within 7 ft horizontally of the top of slope must be capable of supporting the water without soil support. See § 1808.7.3.
  • Foundation top elevation: on graded sites, the top of any exterior foundation shall extend above the street gutter point of discharge or inlet of an approved drainage device by at least 12 in. plus 2%. See § 1808.7.4.
  • Alternate setbacks and clearances are permitted with building official approval; the official may require a geotechnical investigation (see § 1808.7.5).

Other grading / slope controls the code expects you to check

  • Permanent fill slopes generally should not be steeper than 1 vertical in 2 horizontal (50% slope) unless justified by geotechnical engineering — see § 3304.1.1 and Appendix J (J107.6) for fill slope controls and benching/key requirements for fills.

Quick reference table (decision‑relevant values)

Decision item When it matters Key numeric/value to check Code reference
Place fill or surcharge next to building Any time fill/stockpile/backfill is placed adjacent to a structure Only allowed if building can withstand added loads; underpin/protect footings if excavation affects them. Exception: minor grading ≤ 1 ft or walk‑behind equipment. § 1808.3.2
Trigger for slope rules Site has slope above the building Applies where slope > 1V:3H (33.3%) § 1808.7
Very steep slopes — toe location Slope is > 1V:1H (100%) Toe assumed at intersection of horizontal plane from top of foundation and plane tangent to slope at 45°. § 1808.7.1
Pool setbacks from slope Pool adjacent to slope Setback = 1/2 of building footing setback; pool wall within 7 ft must support water without soil support § 1808.7.3
Maximum permanent fill slope (general) Constructing permanent fill slopes Generally no steeper than 1V:2H (50%) unless geotechnical justification § 3304.1.1 and J107.6
Foundation top elevation and drainage Graded site adjacent to street drainage Top of exterior foundation ≥ 12 in. above gutter point of discharge plus 2% § 1808.7.4

Exceptions & special cases

  • Minor landscaping fills (walk‑behind equipment or grade increase ≤1 ft) are allowed without demonstrating structural capacity per the exception to § 1808.3.2 — but larger fills require the building to be proven able to resist the surcharge or the fill must be removed/relocated or the structure strengthened.
  • Alternate setbacks and clearances can be used if approved by the building official; the official may require a geotechnical investigation per § 1808.7.5. If you seek shorter setbacks or steeper fills, plan on submitting a geotechnical report and engineered solutions.
  • Where a retaining wall exists at the toe of the slope the code measures slope height from the top of that retaining wall — that affects the assumed hazard distance. See § 1808.7.1.

Common mistakes

  • Assuming you can place any amount of fill next to a foundation because it’s “landscaping.” The exception is narrow (≤1 ft or walk‑behind) — anything more triggers § 1808.3.2 requirements.
  • Not getting a geotechnical evaluation for slopes steeper than 1:3 or for permanent fills steeper than 1:2. The code explicitly anticipates geotechnical investigation and allows the building official to require it before approving alternate setbacks.
  • Measuring clearances incorrectly on very steep slopes (>1:1). For those slopes the code prescribes a geometric method (45° tangent/horizontal plane) to assume the toe location — don’t rely on a simple horizontal measurement without checking § 1808.7.1.
  • Forgetting to underpin or otherwise protect existing footings when nearby excavation will affect them — § 1808.3.2 requires protection of existing foundations.

Worked example — practical scenario applying the rule with numbers

Scenario: A homeowner wants to add a continuous 2‑ft high landscape fill (compacted soil) directly adjacent to an existing crawlspace foundation; the existing lot above the foundation has a natural slope steeper than 1V:3H.

What the code requires and practical steps:

  1. Exception check: the code’s minor‑grading exception allows grade increases not more than 1 ft (305 mm) by walk‑behind equipment without full compliance. The proposed 2 ft fill exceeds that exception, so the exception does not apply. § 1808.3.2.
  2. Surcharge rule applies: § 1808.3.2 requires that fill/surcharge adjacent to a building be placed only if the building can withstand the added loads and that existing footings affected by excavation be underpinned or otherwise protected. Practically this means you must: (a) stop and obtain a geotechnical/structural evaluation, and (b) either demonstrate the existing foundation and footing can resist the additional lateral/vertical/surcharge loads or design underpinning/retaining elements. § 1808.3.2.
  3. Slope rule applies: because the neighboring slope is steeper than 1V:3H, the foundation clearance/setback provisions of § 1808.7 et seq. must be met; the building official may require a geotechnical report and may require larger setbacks or retaining systems to protect the structure from slope drainage/erosion or shallow failures. § 1808.7 and § 1808.7.5.
  4. Fill slope limits: if the proposed fill faces will be steeper than 1V:2H (50%), Appendix J / § 3304.1.1 require geotechnical justification and benching/keying of the fill; even at 2 ft height, benching or a keyed toe may be required depending on existing slope and soils. § 3304.1.1 and J107.6.

Bottom line for this homeowner: because the proposed fill is >1 ft and the site slope already exceeds 1:3, you cannot simply place the 2‑ft fill next to the foundation. Obtain a geotechnical investigation and structural recommendations, and implement underpinning, retaining walls, controlled compacted fill, or move the fill back (setback) per the geotechnical/engineered design and building official direction. §§ 1808.3.2, 1808.7, 1808.7.5.

Related provisions (quick list)

  • § 1808.3.2 — Surcharge: fill/surcharge adjacent to buildings; underpinning/protection of affected footings.
  • § 1808.7 — Foundations on or adjacent to slopes (applies where slope > 1V:3H).
  • § 1808.7.1 — Building clearance from ascending slopes; measurement rules for very steep slopes and retaining‑wall measurement.
  • § 1808.7.2 — Foundation setback from descending slope surface (embedment/setback in firm material).
  • § 1808.7.3 — Pools and slope setbacks (half the building footing setback + structural requirement within 7 ft).
  • § 1808.7.4 — Foundation elevation relative to street gutter / drainage (12 in. + 2%).
  • § 1808.7.5 — Alternate setbacks/clearances with building‑official approval; geotechnical investigation may be required.
  • § 3304.1.1 — Slope limits for permanent fills and cuts during construction (generally no steeper than 1V:2H without geotechnical justification).
  • Appendix J (J107.3, J107.6, J108) — Grading: benching, fill compaction, maximum fill slope, and setback/ drainage details.

Code references

Grounded in the retrieved California Building Code — click a citation to read the verbatim passage:

  • CBC § 3.3 High relevance — show source text

    1807 A .3.3 Backfill. The backfill in the annular space around columns not embedded in poured footings shall be by one of the following methods:

    1. Backfill shall be of concrete with a specified compressive strength of not less than 2,000 psi (13.8 MPa). The hole shall be not less than 4 inches (102 mm) larger than the diameter of the column at its bottom or 4 inches (102 mm) larger than the diagonal dimension of a square or rectangular column.
    2. Backfill shall be of clean sand. The sand shall be thoroughly compacted by tamping in layers not more than 8 inches (203 mm) in depth.
    3. Backfill shall be of controlled low-strength material (CLSM).

    SECTION 1808 A —FOUNDATIONS

    1808 A .1 General. Foundations shall be designed and constructed in accordance with Sections 1808 A .2 through 1808 A .9. Shallow foundations shall satisfy the requirements of Section 1809 A . Deep foundations shall satisfy the requirements of Section 1810 A .

    1808 A .2 Design for capacity and settlement. Foundations shall be so designed that the allowable bearing capacity of the soil is not exceeded, and that differential settlement is minimized. Foundations in areas with expansive soils shall be designed in accordance with the provisions of Section 1808 A .6.

    The enforcing agency may require an analysis of foundation elements to determine subgrade deformations in order to evaluate their effect on the superstructure, including story drift.

    1808 A .3 Design loads. Foundations shall be designed for the most unfavorable effects due to the combinations of loads specified in Section 2.3 or 2.4 of ASCE 7 or the alternative allowable stress design load combinations of Section 1605 A .2. The dead load is permitted to include the weight of foundations and overlying fill. Reduced live loads, as specified in Sections 1607 A .13 and 1607 A .14, shall be permitted to be used in the design of foundations.

    1808 A .3.1 Seismic overturning. Where foundations are proportioned using the load combinations of Section 2.3 or 2.4 of ASCE 7 and the computation of seismic over-turning effects is by equivalent lateral force analysis or modal analysis, the proportioning shall be in accordance with Section 12.13.4 of ASCE 7.

    1808 A .3.2 Surcharge. Fill or other surcharge loads shall not be placed adjacent to any building or structure unless such building or structure is capable of withstanding the additional loads caused by the fill or the surcharge. Existing footings or foundations that will be affected by any excavation shall be underpinned or otherwise protected against settlement and shall be protected against detrimental lateral or vertical movement or both.

    Exception: Minor grading for landscaping purposes shall be permitted where done with walk-behind equipment, where the grade is not increased more than 1 foot (305 mm) from original design grade or where approved by the building official.

    1808 A .4 Vibratory loads. Where machinery operations or other vibrations are transmitted through the foundation, consideration shall be given in the foundation design to prevent detrimental disturbances of the soil.

  • CBC § 1806.2 High relevance — show source text

    M g = Moment in the post at grade, in foot-pounds (kN-m). S 3 = Allowable lateral soil-bearing pressure as set forth in Section 1806.2 based on a depth equal to the depth of embedment in pounds per square foot (kPa).

    2025 CALIFORNIA BUILDING CODE 18-15

    on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

    SOILS AND FOUNDATIONS

    1807.3.2.3 Vertical load. The resistance to vertical loads shall be determined using the vertical foundation pressure set forth in Table 1806.2.

    1807.3.3 Backfill. The backfill in the annular space around columns not embedded in poured footings shall be by one of the following methods:

    1. Backfill shall be of concrete with a specified compressive strength of not less than 2,000 psi (13.8 MPa). The hole shall be not less than 4 inches (102 mm) larger than the diameter of the column at its bottom or 4 inches (102 mm) larger than the diagonal dimension of a square or rectangular column.
    2. Backfill shall be of clean sand. The sand shall be thoroughly compacted by tamping in layers not more than 8 inches (203 mm) in depth.
    3. Backfill shall be of controlled low-strength material ( CLSM ).

    SECTION 1808—FOUNDATIONS

    1808.1 General. Foundations shall be designed and constructed in accordance with Sections 1808.2 through 1808.9. Shallow foundations shall satisfy the requirements of Section 1809. Deep foundations shall satisfy the requirements of Section 1810. 1808.2 Design for capacity and settlement. Foundations shall be so designed that the allowable bearing capacity of the soil is not exceeded, and that differential settlement is minimized. Foundations in areas with expansive soils shall be designed in accordance with the provisions of Section 1808.6. 1808.3 Design loads. Foundations shall be designed for the most unfavorable effects due to the combinations of loads specified in Section 2.3 or 2.4 of ASCE 7 or the alternative allowable stress design load combinations of Section 1605.2. The dead load is permitted to include the weight of foundations and overlying fill. Reduced live loads, as specified in Sections 1607.13 and 1607.14, shall be permitted to be used in the design of foundations. 1808.3.1 Seismic overturning. Where foundations are proportioned using the load combinations of Section 2.3 or 2.4 of ASCE 7 and the computation of seismic over-turning effects is by equivalent lateral force analysis or modal analysis, the proportioning shall be in accordance with Section 12.13.4 of ASCE 7.

    1808.3.2 Surcharge. Fill or other surcharge loads shall not be placed adjacent to any building or structure unless such building or structure is capable of withstanding the additional loads caused by the fill or the surcharge. Existing footings or foundations that will be affected by any excavation shall be underpinned or otherwise protected against settlement and shall be protected against detrimental lateral or vertical movement or both.

    Exception: Minor grading for landscaping purposes shall be permitted where done with walk-behind equipment, where the grade is not increased more than 1 foot (305 mm) from original design grade or where approved by the building official. **1808.4 Vibratory loads.

  • CBC § 6.4 High relevance — show source text

    1808 A .6.4 Stabilization. Where the active zone of expansive soils is stabilized in lieu of designing foundations in accordance with Section 1808 A .6.1 or 1808 A .6.2, the soil shall be stabilized by chemical, dewatering, presaturation or equivalent techniques.

    1808 A .7 Foundations on or adjacent to slopes. The placement of buildings and structures on or adjacent to slopes steeper than one unit vertical in three units horizontal (33.3-percent slope) shall comply with Sections 1808 A .7.1 through 1808 A .7.5.

    1808 A .7.1 Building clearance from ascending slopes. In general, buildings below slopes shall be set a sufficient distance from the slope to provide protection from slope drainage, erosion and shallow failures. Except as provided in Section 1808 A .7.5 and Figure 1808 A .7.1, the following criteria will be assumed to provide this protection. Where the existing slope is steeper than one unit vertical in one unit horizontal (100-percent slope), the toe of the slope shall be assumed to be at the intersection of a horizontal plane drawn from the top of the foundation and a plane drawn tangent to the slope at an angle of 45 degrees (0.79 rad) to the horizontal. Where a retaining wall is constructed at the toe of the slope, the height of the slope shall be measured from the top of the wall to the top of the slope.

    FIGURE 1808 A .7.1—FOUNDATION CLEARANCES FROM SLOPES

    For SI: 1 foot = 304.8 mm.

    1808 A .7.2 Foundation setback from descending slope surface. Foundations on or adjacent to slope surfaces shall be founded in firm material with an embedment and set back from the slope surface sufficient to provide vertical and lateral support for the foundation without detrimental settlement. Except as provided for in Section 1808 A .7.5 and Figure 1808 A .7.1, the following setback is deemed adequate to meet the criteria. Where the slope is steeper than 1 unit vertical in 1 unit horizontal (100-percent slope), the required setback shall be measured from an imaginary plane 45 degrees (0.79 rad) to the horizontal, projected upward from the toe of the slope.

    18A-12 2025 CALIFORNIA BUILDING CODE

    on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

    SOILS AND FOUNDATIONS

    1808 A .7.3 Pools. The setback between pools regulated by this code and slopes shall be equal to one-half the building footing setback distance required by this section. That portion of the pool wall within a horizontal distance of 7 feet (2134 mm) from the top of the slope shall be capable of supporting the water in the pool without soil support.

  • CBC § 3.1 High relevance — show source text

    1808 A .3.1 Seismic overturning. Where foundations are proportioned using the load combinations of Section 2.3 or 2.4 of ASCE 7 and the computation of seismic over-turning effects is by equivalent lateral force analysis or modal analysis, the proportioning shall be in accordance with Section 12.13.4 of ASCE 7.

    1808 A .3.2 Surcharge. Fill or other surcharge loads shall not be placed adjacent to any building or structure unless such building or structure is capable of withstanding the additional loads caused by the fill or the surcharge. Existing footings or foundations that will be affected by any excavation shall be underpinned or otherwise protected against settlement and shall be protected against detrimental lateral or vertical movement or both.

    Exception: Minor grading for landscaping purposes shall be permitted where done with walk-behind equipment, where the grade is not increased more than 1 foot (305 mm) from original design grade or where approved by the building official.

    1808 A .4 Vibratory loads. Where machinery operations or other vibrations are transmitted through the foundation, consideration shall be given in the foundation design to prevent detrimental disturbances of the soil.

    1808 A .5 Shifting or moving soils. Where it is known that the shallow subsoils are of a shifting or moving character, foundations shall be carried to a sufficient depth to ensure stability.

    2025 CALIFORNIA BUILDING CODE 18A-11

    on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

    SOILS AND FOUNDATIONS

    1808 A .6 Design for expansive soils. Foundations for buildings and structures founded on expansive soils shall be designed in accordance with Section 1808 A .6.1 or 1808 A .6.2.

    Exceptions: Foundation design need not comply with Section 1808 A .6.1 or 1808 A .6.2 where one of the following conditions is satisfied:

    1. The soil is removed in accordance with Section 1808 A .6.3.

    2. The building official approves stabilization of the soil in accordance with Section 1808 A .6.4.

    1808 A .6.1 Foundations. Foundations placed on or within the active zone of expansive soils shall be designed to resist differential volume changes and to prevent structural damage to the supported structure. Deflection and racking of the supported structure shall be limited to that which will not interfere with the usability and serviceability of the structure.

    Foundations placed below where volume change occurs or below expansive soil shall comply with the following provisions:

    1. Foundations extending into or penetrating expansive soils shall be designed to prevent uplift of the supported structure.
    2. Foundations penetrating expansive soils shall be designed to resist forces exerted on the foundation due to soil volume changes or shall be isolated from the expansive soil.

    1808 A .6.2 Slab-on-ground foundations. Moments, shears and deflections for use in designing slab-on-ground, mat or raft foundations on expansive soils shall be determined in accordance with WRI/CRSI or PTI DC 10.5.

  • CBC § 7.1 High relevance — show source text

    Where a retaining wall is constructed at the toe of the slope, the height of the slope shall be measured from the top of the wall to the top of the slope.

    FIGURE 1808 A .7.1—FOUNDATION CLEARANCES FROM SLOPES

    For SI: 1 foot = 304.8 mm.

    1808 A .7.2 Foundation setback from descending slope surface. Foundations on or adjacent to slope surfaces shall be founded in firm material with an embedment and set back from the slope surface sufficient to provide vertical and lateral support for the foundation without detrimental settlement. Except as provided for in Section 1808 A .7.5 and Figure 1808 A .7.1, the following setback is deemed adequate to meet the criteria. Where the slope is steeper than 1 unit vertical in 1 unit horizontal (100-percent slope), the required setback shall be measured from an imaginary plane 45 degrees (0.79 rad) to the horizontal, projected upward from the toe of the slope.

    18A-12 2025 CALIFORNIA BUILDING CODE

    on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

    SOILS AND FOUNDATIONS

    1808 A .7.3 Pools. The setback between pools regulated by this code and slopes shall be equal to one-half the building footing setback distance required by this section. That portion of the pool wall within a horizontal distance of 7 feet (2134 mm) from the top of the slope shall be capable of supporting the water in the pool without soil support.

    1808 A .7.4 Foundation elevation. On graded sites, the top of any exterior foundation shall extend above the elevation of the street gutter at point of discharge or the inlet of an approved drainage device not less than 12 inches (305 mm) plus 2 percent. Alternate elevations are permitted subject to the approval of the building official, provided that it can be demonstrated that required drainage to the point of discharge and away from the structure is provided at all locations on the site.

    1808 A .7.5 Alternate setback and clearance. Alternate setbacks and clearances are permitted, subject to the approval of the building official. The building official shall be permitted to require a geotechnical investigation as set forth in Section 1803 A .5.10.

    1808 A .8 Concrete foundations. The design, materials and construction of concrete foundations shall comply with Sections 1808 A .8.1 through 1808 A .8.6 and the provisions of Chapter 19 A .

    1808 A .8.1 Concrete or grout strength and mix proportioning. Concrete or grout in foundations shall have a specified compressive strength ( f ′ c ) not less than the largest applicable value indicated in Table 1808 A .8.1.

    Where concrete or grout is to be pumped, the mix design including slump shall be adjusted to produce a pumpable mixture.

  • CBC § 3303.1 High relevance — show source text

    SECTION 3303—DEMOLITION

    3303.1 Construction documents. Construction documents and a schedule for demolition shall be submitted where required by the building official. Where such information is required, work shall not be done until such construction documents or schedule, or both, are approved.

    3303.2 Pedestrian protection. The work of demolishing any building shall not be commenced until pedestrian protection is in place as required by this chapter.

    3303.3 Means of egress. A horizontal exit shall not be destroyed unless and until a substitute means of egress has been provided and approved.

    3303.4 Vacant lot. Where a structure has been demolished or removed, the vacant lot shall be filled and maintained to the existing grade or in accordance with the ordinances of the jurisdiction having authority.

    3303.5 Water accumulation. Provision shall be made to prevent the accumulation of water or damage to any foundations on the premises or on adjacent property.

    3303.6 Utility connections. Service utility connections shall be discontinued and capped in accordance with the approved rules and the requirements of the applicable governing authority.

    [F] 3303.7 Fire safety during demolition. Fire safety during demolition shall comply with the applicable requirements of this code and the applicable provisions of Chapter 33 of the California Fire Code .

    SECTION 3304—SITE WORK

    3304.1 Excavation and fill. Excavation and fill for buildings and structures shall be constructed or protected so as not to endanger life or property. Stumps and roots shall be removed from the soil to a depth of not less than 12 inches (305 mm) below the surface of the ground in the area to be occupied by the building. Wood forms that have been used in placing concrete, if within the ground or between foundation sills and the ground, shall be removed before a building is occupied or used for any purpose. Before completion, loose or casual wood shall be removed from direct contact with the ground under the building.

    3304.1.1 Slope limits. Slopes for permanent fill shall be not steeper than one unit vertical in two units horizontal (50-percent slope). Cut slopes for permanent excavations shall be not steeper than one unit vertical in two units horizontal (50-percent slope). Deviation from the foregoing limitations for cut slopes shall be permitted only upon the presentation of a soil investigation report acceptable to the building official.

    33-4 2025 CALIFORNIA BUILDING CODE

    on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

    SAFEGUARDS DURING CONSTRUCTION

    3304.1.2 Surcharge. Fill or other surcharge loads shall not be placed adjacent to any building or structure unless such building or structure is capable of withstanding the additional loads caused by the fill or surcharge. Existing footings or foundations that can be affected by any excavation shall be underpinned adequately or otherwise protected against settlement and shall be protected against lateral movement.

    3304.1.3 Footings on adjacent slopes. For footings on adjacent slopes, see Chapter 18.

    3304.1.4 Fill supporting foundations. Fill to be used to support the foundations of any building or structure shall comply with Section 1804.6. Special inspections of compacted fill shall be in accordance with Section 1705.6.

  • CBC § 3304.1.1 High relevance — show source text

    3304.1.1 Slope limits. Slopes for permanent fill shall be not steeper than one unit vertical in two units horizontal (50-percent slope). Cut slopes for permanent excavations shall be not steeper than one unit vertical in two units horizontal (50-percent slope). Deviation from the foregoing limitations for cut slopes shall be permitted only upon the presentation of a soil investigation report acceptable to the building official.

    33-4 2025 CALIFORNIA BUILDING CODE

    on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

    SAFEGUARDS DURING CONSTRUCTION

    3304.1.2 Surcharge. Fill or other surcharge loads shall not be placed adjacent to any building or structure unless such building or structure is capable of withstanding the additional loads caused by the fill or surcharge. Existing footings or foundations that can be affected by any excavation shall be underpinned adequately or otherwise protected against settlement and shall be protected against lateral movement.

    3304.1.3 Footings on adjacent slopes. For footings on adjacent slopes, see Chapter 18.

    3304.1.4 Fill supporting foundations. Fill to be used to support the foundations of any building or structure shall comply with Section 1804.6. Special inspections of compacted fill shall be in accordance with Section 1705.6.

    3304.1.5 [HCD 1] Storm water drainage and retention during construction. Projects which disturb less than one acre of soil and are not part of a larger common plan of development which in total disturbs one acre or more, shall manage storm water drainage during construction in accordance with the California Green Building Standards Code (CALGreen), Chapter 4, Division 4.1.

    SECTION 3305—SANITARY

    3305.1 Facilities required. Sanitary facilities shall be provided during construction, remodeling or demolition activities in accordance with the California Plumbing Code .

    SECTION 3306—PROTECTION OF PEDESTRIANS

    [BS] 3306.1 Protection required. Pedestrians shall be protected during construction, remodeling and demolition activities as required by this chapter and Table 3306.1. Signs shall be provided to direct pedestrian traffic.

    TABLE 3306.1—PROTECTION OF PEDESTRIANS Col2 Col3
    HEIGHT OF CONSTRUCTION DISTANCE FROM CONSTRUCTION TO LOT LINE TYPE OF PROTECTION REQUIRED
    8 feet or less Less than 5 feet Construction railings
    8 feet or less 5 feet or more None
    More than 8 feet Less than 5 feet Barrier and covered walkway
    More than 8 feet 5 feet or more, but not more than one-fourth the height of
    construction    		 Barrier and covered walkway
    More than 8 feet 5 feet or more, but between one-fourth and one-half the height
    of construction    		 Barrier
    More than 8 feet 5 feet or more, but exceeding one-half the height of construction None
    For SI: 1 foot = 304.8 mm. For SI: 1 foot = 304.8 mm. For SI: 1 foot = 304.8 mm.
  • CBC § 1006.2.2.1 Medium relevance — show source text

    Exits 1006.2.2.1

    Bolts

    Anchor rods 1901.3 Bonding, Masonry 1805.2.2, 2103.2.2, 2113.3.1, 2510.7 Bottle-Filling Stations 202 Braced Wall Line 202

    Bracing 2308.10 Seismic requirements 2308.10.10.2, 2308.10.6.2, 2308.10.8 Sill anchorage 2308.10.7.3 Spacing 2308.10.1 Support 2308.10.8 Temporary 3103.5 Braced Wall Panel 202 Alternative bracing 2308.10.5.1, 2308.10.5.2

    Connections 2308.10.7 Length 2308.10.4 Location 2308.10.2

    Method 2308.10.3 Brick (see Masonry) Building Area (see Area, Building) 502.1, 503, 505, 506, 507, 508, 510 Demolition 3303

    Existing 101.4.7 Fire walls 706.1 Height (see Height, Building) 502.1, 503, 504, 505, 508, 510 Occupancy classification Chapter 3 Party walls 706.1.1 Relocatable 3113

    Replicable Appendix N Building, Existing 202 Building Department 103 Building Official Duties and powers 103, 104 Qualifications Appendix A Records 104.7

    Termination A101.4 Building-Integrated Photovoltaic (BIPV) (see Photovoltaic) Built-Up Roof 1507.10 Business Occupancy (Group B) 303.1.1, 303.1.2, 304 Alarms and detection 907.2.2 Ambulatory care facilities 304, 422 Area 503, 505, 506, 507, 508 Height 503, 504, 505, 508, 510 Higher education laboratories 428, 2702.2

    Incidental uses 509 Interior finishes Table 803.13, 804 Live load Table 1607.1 Means of egress Aisles 1018.3

    Stairway, exit access 1019 Travel distance 1006.3, 1017.2,

    1006.2.1

    Mixed occupancies 508.2, 508.3, 508.4 Accessory 303.1.2, 508.2 Ambulatory care facilities 422 Assembly 303.1.2

    Assembly spaces 1030 Exit signs 1013.1 Guards 1015.2, 1030.17 Main exit 1030.3

  • CBC § 2.34 Medium relevance — show source text

    where:

    A = 2.34 P /( S 1 b ).

    b = Diameter of round post or footing or diagonal dimension of square post or footing, feet (m).

    d = Depth of embedment in earth in feet (m) but not over 12 feet (3658 mm) for purpose of computing lateral pressure.

    h = Distance in feet (m) from ground surface to point of application of “ P .”

    P = Applied lateral force in pounds (kN).

    S 1 = Allowable lateral soil-bearing pressure as set forth in Section 1806 A .2 based on a depth of one-third the depth of embedment in pounds per square foot (psf) (kPa).

    1807 A .3.2.2 Constrained. The following formula shall be used to determine the depth of embedment required to resist lateral loads where lateral constraint is provided at the ground surface, such as by a rigid floor or slab-on-ground.

    Equation 18 A -2

    or alternatively

    Equation 18 A -3 d = ----------------- g - where: 3

    M g = Moment in the post at grade, in foot-pounds (kN-m). S 3 = Allowable lateral soil-bearing pressure as set forth in Section 1806.2 based on a depth equal to the depth of embedment in pounds per square foot (kPa).

    1807 A .3.2.3 Vertical load. The resistance to vertical loads shall be determined using the vertical foundation pressure set forth in Table 1806 A .2.

    1807 A .3.3 Backfill. The backfill in the annular space around columns not embedded in poured footings shall be by one of the following methods:

    1. Backfill shall be of concrete with a specified compressive strength of not less than 2,000 psi (13.8 MPa). The hole shall be not less than 4 inches (102 mm) larger than the diameter of the column at its bottom or 4 inches (102 mm) larger than the diagonal dimension of a square or rectangular column.
    2. Backfill shall be of clean sand. The sand shall be thoroughly compacted by tamping in layers not more than 8 inches (203 mm) in depth.
    3. Backfill shall be of controlled low-strength material (CLSM).

    SECTION 1808 A —FOUNDATIONS

    1808 A .1 General. Foundations shall be designed and constructed in accordance with Sections 1808 A .2 through 1808 A .9. Shallow foundations shall satisfy the requirements of Section 1809 A . Deep foundations shall satisfy the requirements of Section 1810 A .

    1808 A .2 Design for capacity and settlement. Foundations shall be so designed that the allowable bearing capacity of the soil is not exceeded, and that differential settlement is minimized. Foundations in areas with expansive soils shall be designed in accordance with the provisions of Section 1808 A .6.

    The enforcing agency may require an analysis of foundation elements to determine subgrade deformations in order to evaluate their effect on the superstructure, including story drift.

  • CBC § 8.5 Medium relevance — show source text

    1808 A .8.5 Forming of concrete. Concrete foundations are permitted to be cast against the earth where, in the opinion of the building official, soil conditions do not require formwork. Where formwork is required, it shall be in accordance with Section 26.11 of ACI 318.

    1808 A .8.6 Seismic requirements. See Section 1905 A for additional requirements for foundations of structures assigned to Seismic Design Category D, E or F.

    For structures assigned to Seismic Design Category D, E or F, provisions of Section 18.13 of ACI 318 shall apply where not in conflict with the provisions of Sections 1808 A through 1810 A .

    1808 A .9 Vertical masonry foundation elements. Vertical masonry foundation elements that are not foundation piers as defined in Section 202 shall be designed as piers, walls or columns, as applicable, in accordance with TMS 402.

    SECTION 1809 A —SHALLOW FOUNDATIONS

    1809 A .1 General. Shallow foundations shall be designed and constructed in accordance with Sections 1809 A .2 through 1809 A . 15 .

    1809 A .2 Supporting soils. Shallow foundations shall be built on undisturbed soil, compacted fill material or controlled low-strength material (CLSM). Compacted fill material shall be placed in accordance with Section 1804 A .6. CLSM shall be placed in accordance with Section 1804 A .7.

    1809 A .3 Stepped footings. The top surface of footings shall be level. The bottom surface of footings shall be permitted to have a slope not exceeding 1 unit vertical in 10 units horizontal (10-percent slope). Footings shall be stepped where it is necessary to change the elevation of the top surface of the footing or where the surface of the ground slopes more than 1 unit vertical in 10 units horizontal (10-percent slope).

    Individual steps in continuous footings shall not exceed 18 inches (457 mm) in height and the slope of a series of such steps shall not exceed 1 unit vertical to 2 units horizontal (50 percent slope) unless otherwise recommended by a geotechnical report. The steps shall be detailed on the drawings. The local effects due to the discontinuity of the steps shall be considered in the design of the foundation.

    1809 A .4 Depth and width of footings. The minimum depth of footings below the undisturbed ground surface shall be 12 inches (305 mm). Where applicable, the requirements of Section 1809 A .5 shall be satisfied. The minimum width of footings shall be 12 inches (305 mm).

    1809 A .5 Frost protection. Except where otherwise protected from frost, foundations and other permanent supports of buildings and structures shall be protected from frost by one or more of the following methods:

    1. Extending below the frost line of the locality.
    2. Constructing in accordance with ASCE 32.
    3. Erecting on solid rock.
  • CBC § 8.2 Medium relevance — show source text

    1808 A .8.2 Concrete cover. The concrete cover provided for prestressed and nonprestressed reinforcement in foundations shall be not less than the largest applicable value specified in Table 1808 A .8.2. Longitudinal bars spaced less than 1 [1] / 2 inches (38 mm) clear distance apart shall be considered to be bundled bars for which the concrete cover provided shall be not less than that required by Section 20.5.1.3.5 of ACI 318. Concrete cover shall be measured from the concrete surface to the outermost surface of the steel to which the cover requirement applies. Where concrete is placed in a temporary or permanent casing or a mandrel, the inside face of the casing or mandrel shall be considered to be the concrete surface.

    TABLE 1808A.8.2—MINIMUM CONCRETE COVER Col2
    FOUNDATION ELEMENT OR CONDITION MINIMUM COVER
    1. Shallow foundations In accordance with Section 20.5 of ACI 318
    2. Precast nonprestressed deep foundation elements
    Exposed to seawater
    Not manufactured under plant conditions
    Manufactured under plant control conditions    		 3 inches
    2 inches
    In accordance with Section 20.5.1.3.3 of ACI 318
    3. Precast prestressed deep foundation elements
    Exposed to seawater
    Other    		 2.5 inches
    In accordance with Section 20.5.1.3.3 of ACI 318
    4. Cast-in-place deep foundation elements not enclosed by a steel pipe, tube or permanent
    casing    		 2.5 inches
    5. Cast-in-place deep foundation elements enclosed by a steel pipe, tube or permanent casing 1 inch
    6. Structural steel core within a steel pipe, tube or permanent casing 2 inches
    7. Cast-in-place drilled shafts enclosed by a stable rock socket 1.5 inches
    For SI:1 inch = 25.4 mm. For SI:1 inch = 25.4 mm.

    1808 A .8.3 Placement of concrete. Concrete shall be placed in such a manner as to ensure the exclusion of any foreign matter and to secure a full-size foundation. Concrete shall not be placed through water unless a tremie or other method approved by the building official is used. Where placed under or in the presence of water, the concrete shall be deposited by approved means to ensure minimum segregation of the mix and negligible turbulence of the water. Where depositing concrete from the top of a deep foundation element, the concrete shall be chuted directly into smooth-sided pipes or tubes or placed in a rapid and continuous operation through a funnel hopper centered at the top of the element.

    2025 CALIFORNIA BUILDING CODE 18A-13

    on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

    SOILS AND FOUNDATIONS

    1808 A .8.4 Protection of concrete. Concrete foundations shall be protected from freezing during depositing and for a period of not less than 5 days thereafter. Water shall not be allowed to flow through the deposited concrete.

  • CBC § 0.083 Medium relevance — show source text

    Minimum fastener size. Corrosion-resistant nails not less than No. 11 gage with5/16-inch head. Fasteners shall be long enough to penetrate into the sheathing3/4 inch or
    through the thickness of the sheathing, whichever is less. Attaching wire for clay and concrete tile shall not be smaller than 0.083 inch.
    b. Snow areas. Not fewer than two fasteners per tile are required or battens and one fastener.
    c. Roof slopes greater than 24:12. The nose of all tiles shall be securely fastened.
    d. Horizontal battens. Battens shall be not less than 1 inch by 2 inches nominal. Provisions shall be made for drainage by a riser of not less than1/8 inch at each nail or by 4-foot-
    long battens with not less than a1/2-inch separation between battens. Horizontal battens are required for slopes over 7:12.
    e. Perimeter fastening areas include three tile courses but not less than 36 inches from either side of hips or ridges and edges of eaves and_gable_ rakes.
    f._ Vasd_ shall be determined in accordance with Section 1609.3.1.|

    15-12 2025 CALIFORNIA BUILDING CODE

    on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

    ROOF ASSEMBLIES AND ROOFTOP STRUCTURES

    1507.3.8 Application. Tile shall be applied according to the manufacturer’s installation instructions, based on the following:

    1. Climatic conditions.

    2. Roof slope.

    3. Underlayment system.

    4. Type of tile being installed.

    1507.3.9 Flashing. At the juncture of the roof vertical surfaces, flashing and counterflashing shall be provided in accordance with the manufacturer’s installation instructions, and where of metal, shall be not less than 0.019-inch (0.48 mm) (No. 26 galvanized sheet gage) corrosion-resistant metal. The valley flashing shall extend not less than 11 inches (279 mm) from the centerline each way and have a splash diverter rib not less than 1 inch (25 mm) high at the flow line formed as part of the flashing. Sections of flashing shall have an end lap of not less than 4 inches (102 mm). For roof slopes of three units vertical in 12 units horizontal (25-percent slope) and over, the valley flashing shall have a 36-inch-wide (914 mm) underlayment of either one layer of Type I underlayment running the full length of the valley, or a self-adhering polymer-modified bitumen sheet bearing a label indicating compliance with ASTM D1970, in addition to other required underlayment. In areas where the average daily temperature in January is 25°F (-4°C) or less or where there is a possibility of ice forming along the eaves causing a backup of water, the metal valley flashing underlayment shall be solid cemented to the roofing underlayment for slopes under seven units vertical in 12 units horizontal (58-percent slope) or self-adhering polymer-modified bitumen sheet shall be installed.

Frequently asked questions

Can I add a small berm next to my foundation for landscaping?

Yes — minor grading for landscaping is permitted under the exception to § 1808.3.2 where the grade increase is not more than 1 foot or is done with walk‑behind equipment; anything beyond that requires you to follow § 1808.3.2 (demonstrate the building can resist the surcharge or provide protection).

My lot has a steep slope above the house — how far back must the house be?

If the slope is steeper than 1V:3H the clearance/setback rules of § 1808.7 apply; for very steep slopes (>1V:1H) the code prescribes a geometric method (45° tangent/horizontal plane) to assume the toe. The code also allows alternate setbacks with a geotechnical report and building‑official approval. You need a site‑specific geotechnical evaluation to determine the safe setback.

Can I rely on a contractor’s grading plan without a geotechnical report?

If grading or fill/slope conditions exceed the minor‑grading exception, the building official may require a geotechnical investigation; for slopes >1:3 or fills steeper than 1:2 (or other nonstandard conditions) a geotechnical report is commonly required by the code. § 1808.7.5, § 3304.1.1, Appendix J.

Do I have to underpin my foundation if I excavate next to it?

Yes — § 1808.3.2 requires existing footings or foundations that will be affected by any excavation to be underpinned or otherwise protected against settlement and lateral/vertical movement.

If there is a retaining wall at the toe of a slope, does that change measurement?

Yes — where a retaining wall is constructed at the toe, the code measures slope height from the top of the wall (see § 1808.7.1).

More in California Building Code

Ask about the CBC

Get cited, plain-English answers on the California Building Code for your project — any code section, any scenario.

Start Free Trial

Related in the CBC

What are the requirements for excavation, grading, compaction and fills?

How must foundations be protected from groundwater and moisture?

Site Preparation, Excavation, Grading, Fill & Moisture Protection

California Building Code