CRC · California Residential Code

How are concrete and masonry foundation walls selected and sized (thickness, reinforcement)?

Q: When can I use a 6‑inch concrete foundation wall?

A 6‑inch nominal concrete stem wall is permitted in prescriptive provisions when the wall is monolithic with slab‑on‑grade and the unbalanced backfill retained by the stem wall is greater than 18 in , per § R404.1.3.2.1 — subject to the other table limits and SDC considerations.

Q: If I have brick veneer on top of a foundation wall, does that change wall thickness?

Yes — § R404.1.5.1 allows masonry foundation walls of 8‑inch nominal thickness under brick‑veneered frame walls (and other limited cases) provided other conditions in that section are met. Also concrete foundation walls must be at least as thick as the wall above per § R404.1.5.2 .

For a homeowner: the CRC gives prescriptive tables to pick foundation wall thickness and reinforcement. If your wall will hold more than 4 feet of soil, be taller than 8 feet, or is in higher seismic zones, the plain (unreinforced) options vanish and the code requires specific bar sizes/spacing or an engineered design. Consult the tables in **§ R404.1.2.1** (masonry) and **§ R404.1.3** (concrete) or hire an engineer when the table limits are exceeded.

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Last reviewed: July 6, 2026

What the code requires — 2-4 sentences

In plain language: masonry foundation walls are selected and sized using the prescriptive masonry foundation provisions in § R404.1.2 and the detailed tables in § R404.1.2.1, and concrete foundation walls are selected and sized using the provisions in § R404.1.3. The code distinguishes plain (unreinforced) walls from reinforced walls by wall height, unbalanced backfill height, seismic design category and soil lateral loads; when limits for plain walls are exceeded the tables in the cited sections require specific bar sizes and spacing or an engineered design. See § R404.1.2, § R404.1.2.1 and § R404.1.3 for the controlling rules.

The single most important practical rule: if your foundation wall will retain more than 4 ft of unbalanced backfill, exceed 8 ft in unsupported height, or is in a higher seismic category, you must move from the “plain” wall allowances and follow the reinforcement tables or an engineered design.

Key defined terms (first use)

Unbalanced backfill — difference between exterior finish ground and interior slab/top of footing as defined in the tables' notes. See § R404.1.2.1.
Plain masonry / plain concrete — walls built without the longitudinal reinforcement required by the tables; allowed only within the stated height/backfill limits in the cited sections. See § R404.1.2.1 and § R404.1.3.

Requirements in detail

Below are the decision‑relevant limits and reinforcement rules the CRC uses to pick wall thickness and reinforcement. Always consult the full tables in § R404.1.2.1 (masonry) and § R404.1.3.2 (concrete) for the precise bar sizes and spacings applicable to your soil class, wall height and retained fill.

Masonry foundation walls (selection & sizing)

Masonry foundation walls are designed per § R404.1.2; detailed prescriptive options are in § R404.1.2.1 and Tables R404.1.2.1(1)–(4).
In Seismic Design Categories D0, D1, D2, additional mandatory requirements apply:
- Maximum wall height for plain masonry: 8 ft. Maximum unbalanced backfill for plain masonry: 4 ft. Minimum nominal thickness for plain masonry in these SDCs: 8 in. See § R404.1.4.1.
- Masonry stem walls in those SDCs must have at least one No. 4 vertical bar not greater than 4 ft on center in grouted cells, and vertical bars must be tied to footing horizontal reinforcement. Also, when walls support more than 4 ft unbalanced backfill or exceed 8 ft height, walls must be constructed in accordance with Tables R404.1.2.1(2)–(4).
Horizontal joint reinforcement minimums (general masonry practice and where the tables require prescriptive reinforcement) are specified by Chapter R606; typical minimums include two W1.7 wires for walls >4 in wide or one W1.7 for ≤4 in walls, placed within the top/bottom 16 in. See R606 provisions referenced from R404.1.2.1.

Concrete foundation walls (selection & sizing)

Concrete foundation walls are sized and reinforced following § R404.1.3 and its prescriptive tables (R404.1.3.2 series) when the conditions fall within the prescriptive scope.
In Seismic Design Categories D0, D1, D2:
- Plain concrete walls supporting light-frame walls: maximum wall height 8 ft, maximum unbalanced backfill 4 ft, minimum plain wall thickness 7.5 in (unless reduced to 6 in where max wall height is 4 ft 6 in). See § R404.1.4.2.
Stem walls that are monolithic with slabs-on-ground (laterally supported at top) have different minimum thickness rules; for example, where unbalanced backfill retained by the stem wall is greater than 18 in, the minimum nominal thickness is 6 in per the prescriptive concrete tables. See § R404.1.3.2.1.
When a plain concrete wall is thinner than the plain‑wall minimum or exceeds the plain‑wall backfill/height limits, the tables in § R404.1.3.2 require horizontal and vertical reinforcement (bar sizes and spacings) or an engineered design (see the DR entries in the tables).

Reinforcement — general prescriptive rules

Reinforcing steel sizing and spacing in the CRC tables is based on Grade 60 bars unless otherwise noted; bar spacing shall not exceed 48 in on center and shall be not less than one-half the nominal wall thickness. Use Table R404.1.3.2(9) to adjust spacing for different bar grades/sizes. See § R404.1.3 notes.
Masonry horizontal reinforcement minimums and locations (for prescriptive reinforced masonry) are specified in Section R606 (joint and bond‑beam reinforcement) and cross‑referenced from R404.1.2.1. Typical required horizontal reinforcement for masonry in SDC D categories: two No. 4 horizontal bars in the upper 12 in where the wall supports >4 ft unbalanced backfill or exceeds 8 ft. See § R404.1.4.1 and R606.
Construction joints, concrete cover and placement tolerances are specified in the concrete foundation provisions; for example concrete cover for reinforcement measured from the inside face is not less than 3/4 in, and measured from the outside face not less than 1-1/2 in for No.5 and smaller bars (see R404.1.3 notes). When construction joints are used, at least one No.4 bar must extend across the joint at spacing not exceeding 24 in and with 12 in embedment each side. See § R404.1.3.3.7.8.

Decision summary — quick reference table

Condition / trigger	Prescriptive minimum thickness / reinforcement	Code reference
Plain masonry in SDC D0/D1/D2 (plain allowed)	Minimum nominal thickness 8 in; plain walls limited to ≤ 8 ft height and ≤ 4 ft unbalanced backfill	§ R404.1.4.1
Masonry supporting >4 ft unbalanced backfill or >8 ft height	Must use Tables R404.1.2.1(2)–(4) (reinforced designs); two No.4 horizontal bars in upper 12 in required in these cases	§ R404.1.2.1 and § R404.1.4.1
Plain concrete walls in SDC D0/D1/D2 (light-frame support)	Min plain thickness 7.5 in; 6 in permitted where maximum wall height is 4 ft 6 in; plain limited to ≤ 8 ft height and ≤ 4 ft unbalanced backfill	§ R404.1.4.2
Monolithic concrete stem wall, unbalanced backfill > 18 in	Minimum nominal thickness 6 in (see R404.1.3.2.1)	§ R404.1.3.2.1
Vertical bar spacing maximum (general)	≤ 48 in on center; spacing not less than 1/2 wall thickness; use Table R404.1.3.2(9) for alternate grades/sizes	§ R404.1.3 notes
Note: the full prescriptive tables contain many combinations of soil class, wall height and backfill; consult Tables R404.1.2.1(1)–(4) and R404.1.3.2 series for the precise bar sizes/spacing applicable to your case.

Exceptions & special cases

If the wall is subject to hydrostatic pressure or supports more than 48 in (4 ft) of unbalanced backfill without permanent lateral support, an engineered design is required and the prescriptive tables cannot be used. See § R404.1.1.
Pier and curtain‑wall foundations: load-bearing masonry walls with minimum actual thickness 4 in (nominal) are permitted under limited conditions (piers, bonding, max heights, limited unbalanced fill). See R404.1.5.3 (referenced from R404.1.5).
Seismic Design Categories C, D0–D2 impose additional restrictions: some prescriptive tables are not permitted for higher seismic categories (or different standards apply); see § R404.1.3.4 and § R404.1.4. Where the tables are not applicable the walls must comply with ACI 318 / ACI 332 / PCA 100 or an engineered design.

Common mistakes

Assuming the foundation wall can be the same thickness as a non‑retaining above‑grade wall — CRC explicitly requires foundation thickness to be at least the thickness of the supported wall but also imposes additional minimums for masonry and concrete. See § R404.1.5.1 and § R404.1.5.2.
Failing to check the unbalanced backfill measurement rules (exterior finish grade to lower of top of footing or interior slab). The measurement method affects whether a wall triggers reinforcement requirements. See Table notes in § R404.1.2.1.
Using prescriptive plain‑wall allowances beyond their limits (height, backfill, seismic category). When limits are exceeded, you must use the tables for reinforced walls or provide an engineered design. See § R404.1.2.1 and § R404.1.3.
Incorrect concrete cover or bar placement: the code specifies minimum cover and tolerances for d (effective depth) and for cover from both inside and outside faces. Check the notes to the tables in § R404.1.3.2.

Worked example — concrete scenario applying the rule with numbers

Scenario: single‑family house located in Seismic Design Category B. You have a concrete stem wall that is monolithic with the slab‑on‑grade, will retain 24 in (2 ft) of unbalanced backfill, and the unsupported wall height is 5 ft. What is the minimum nominal wall thickness (prescriptive)?

Step 1 — Determine which section applies:

This is a concrete foundation wall → use § R404.1.3 and the prescriptive stem‑wall rules.

Step 2 — Check monolithic stem‑wall exception:

§ R404.1.3.2.1 says where unbalanced backfill retained by a stem wall is greater than 18 in, the minimum nominal thickness of the wall shall be 6 in (for walls laterally supported at top by slabs‑on‑ground). Our case (24 in) exceeds 18 in, and the wall is monolithic, so the prescriptive minimum is 6 in.

Step 3 — Check plain‑wall limits for SDC D restrictions:

We are SDC B, so the SDC D prohibitions on plain walls do not apply; plain concrete is acceptable per the prescriptive limits in this SDC. See § R404.1.4.2 for the D‑category rules (not limiting our SDC).

Conclusion: Minimum nominal thickness (prescriptive) = 6 in, provided the wall meets the placement, cover and reinforcement (if any) requirements in the applicable concrete tables and notes. If any other trigger is present (e.g., higher lateral soil loads, hydrostatic pressure, openings, or different soil class), the prescriptive table or an engineered design must be used.

Related provisions (quick list)

§ R404.1.2 — Design of masonry foundation walls (prescriptive scope).
§ R404.1.2.1 — Tables for plain and reinforced masonry foundation walls (R404.1.2.1(1)–(4)).
§ R404.1.3 — Concrete foundation walls and prescriptive tables (R404.1.3.2 series and notes).
§ R404.1.4.1 / § R404.1.4.2 — Additional requirements for Seismic Design Categories D0, D1, D2 (masonry and concrete).
§ R404.1.5 / R404.1.5.1 / R404.1.5.2 — Foundation wall thickness based on the wall supported (masonry and concrete).
Chapter R606 — Masonry reinforcement, horizontal joint reinforcement and bond‑beam rules referenced by R404.1.2.1.
Section R608 — Above‑grade concrete wall reinforcement rules referenced by some stem‑wall provisions.

If you need a code‑boxed printout of the exact table rows that apply to your wall height, soil class and backfill situation, tell me: provide the wall height, unbalanced backfill height, soil classification (per Table R401.4.1(2) if known), whether the stem wall is monolithic with slab, and the seismic design category — I’ll pull the exact table entries that govern your case. (Note: I will quote the specific table rows from the CRC text.)

Code references

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

CRC § 1.2.1 High relevance — show source text
Foundation walls, supporting more than 4 feet (1219 mm) of unbalanced backfill or exceeding 8 feet (2438 mm) in height shall be constructed in accordance with Table R404.1.2.1(2), R404.1.2.1(3) or R404.1.2.1(4). Masonry foundation walls shall have two No. 4 (No. 13) horizontal bars located in the upper 12 inches (305 mm) of the wall.

R404.1.4.2 Concrete foundation walls. In buildings assigned to Seismic Design Category D 0, D 1 or D 2, as established in Table R301.2, concrete foundation walls that support light-frame walls shall comply with this section, and concrete foundation walls that support above-grade concrete walls shall comply with ACI 318, ACI 332 or PCA 100 (see Section R404.1.3). In addition to the horizontal reinforcement required by Table R404.1.3.2(1), plain concrete walls supporting light-frame walls shall comply with the following:
1. Wall height shall not exceed 8 feet (2438 mm).
2. Unbalanced backfill height shall not exceed 4 feet (1219 mm).
3. Minimum thickness for plain concrete foundation walls shall be 7.5 inches (191 mm) except that 6 inches (152 mm) is permitted where the maximum wall height is 4 feet 6 inches (1372 mm).
Foundation walls less than 7.5 inches (191 mm) in thickness, supporting more than 4 feet (1219 mm) of unbalanced backfill or exceeding 8 feet (2438 mm) in height shall be provided with horizontal reinforcement in accordance with Table R404.1.3.2(1), and vertical reinforcement in accordance with Table R404.1.3.2(2), R404.1.3.2(3), R404.1.3.2(4), R404.1.3.2(5), R404.1.3.2(6), R404.1.3.2(7) or R404.1.3.2(8). Where Tables R404.1.3.2(2) through R404.1.3.2(8) permit plain concrete walls, not less than No. 4 (No. 13) vertical bars at a spacing not exceeding 48 inches (1219 mm) shall be provided.

R404.1.5 Foundation wall thickness based on walls supported. The thickness of masonry or concrete foundation walls shall be not less than that required by Section R404.1.5.1 or R404.1.5.2, respectively.

R404.1.5.1 Masonry wall thickness. Masonry foundation walls shall be not less than the thickness of the wall supported, except that masonry foundation walls of not less than 8-inch (203 mm) nominal thickness shall be permitted under brick veneered frame walls and under 10-inch-wide (254 mm) cavity walls where the total height of the wall supported, including gables, is not more than 20 feet (6096 mm), provided that the requirements of Section R404.1.1 are met.

R404.1.5.2 Concrete wall thickness. The thickness of concrete foundation walls shall be equal to or greater than the thickness of the wall in the story above. Concrete foundation walls with corbels, brackets or other projections built into the wall for support of masonry veneer or other purposes are not within the scope of the tables in this section.
CRC § 1807.1.6.2. High relevance — show source text
Provisions for this table are based on design and construction requirements specified in Section 1807.1.6.2.
c. PC = Plain Concrete.
d. Where unbalanced backfill height exceeds 8 feet and design lateral soil loads from Table 1610.1 are used, the requirements for 30 and 45 psf per foot of depth are not applica-
ble (see Section 1610).
e. For height of unbalanced backfill, see Section 1807.1.2.|

1807.1.6.2.1 Seismic requirements. Based on the seismic design category assigned to the structure in accordance with Section 1613, concrete foundation walls designed using Table 1807.1.6.2 shall be subject to the following limitations:
1. Seismic Design Categories A and B. Not less than one No. 5 bar shall be provided around window, door and similar sized openings. The bar shall be anchored to develop f y in tension at the corners of openings.
2. Seismic Design Categories C, D, E and F. Tables shall not be used except as allowed for plain concrete members in Section 1905.6.2.
1807.1.6.3 Masonry foundation walls. Masonry foundation walls shall comply with the following:
1. The thickness shall comply with the requirements of Table 1807.1.6.3(1) for plain masonry walls or Table 1807.1.6.3(2), 1807.1.6.3(3) or 1807.1.6.3(4) for masonry walls with reinforcement.
2. Vertical reinforcement shall have a minimum yield strength of 60,000 psi (414 MPa).
3. The specified location of the reinforcement shall equal or exceed the effective depth distance, d, noted in Tables 1807.1.6.3(2), 1807.1.6.3(3) and 1807.1.6.3(4) and shall be measured from the face of the exterior (soil) side of the wall to the center of the vertical reinforcement. The reinforcement shall be placed within the tolerances specified in TMS 602 for the specified location.
4. Grout shall comply with Section 2103.3.
5. Concrete masonry units shall comply with ASTM C90.
6. Clay masonry units shall comply with ASTM C652 for hollow brick, except compliance with ASTM C62 or ASTM C216 shall be permitted where solid masonry units are installed in accordance with Table 1807.1.6.3(1) for plain masonry.
7. Masonry units shall be laid in running bond and installed with Type M or S mortar in accordance with Section 2103.2.1.
8. The unfactored axial load per linear foot of wall shall not exceed 1.2 tf′ m where t is the specified wall thickness in inches and f′ m is the specified compressive strength of masonry in pounds per square inch.
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1. Not less than 4 inches (102 mm) of solid masonry shall be provided at girder supports at the top of hollow masonry unit foundation walls.
CRC § 1807.1.4 High relevance — show source text
1807.1.4 Permanent wood foundation systems. [OSHPD 1R, 2 & 5] Not permitted by OSHPD. Permanent wood foundation systems shall be designed and installed in accordance with AWC PWF. Lumber and plywood shall be preservative treated in accordance with AWPA U1 (Commodity Specification A, Special Requirement 4.2) and shall be identified in accordance with Section 2303.1.9.1.

1807.1.5 Concrete and masonry foundation walls. Concrete and masonry foundation walls shall be designed in accordance with Chapter 19 or 21, as applicable.

Exception: [OSHPD 1R, 2 & 5] Not permitted by OSHPD. Concrete and masonry foundation walls shall be permitted to be designed and constructed in accordance with Section 1807.1.6.

1807.1.6 Prescriptive design of concrete and masonry foundation walls. [OSHPD 1R, 2 & 5] Not permitted by OSHPD. Concrete and masonry foundation walls that are laterally supported at the top and bottom shall be permitted to be designed and constructed in accordance with this section.

1807.1.6.1 Foundation wall thickness. The thickness of prescriptively designed foundation walls shall be not less than the thickness of the wall supported, except that foundation walls of not less than 8-inch (203 mm) nominal width shall be permitted to support brick-veneered frame walls and 10-inch-wide (254 mm) cavity walls provided that the requirements of Section 1807.1.6.2 or 1807.1.6.3 are met.

1807.1.6.2 Concrete foundation walls. Concrete foundation walls shall comply with the following:
1. The thickness shall comply with the requirements of Table 1807.1.6.2.
2. The size and spacing of vertical reinforcement shown in Table 1807.1.6.2 are based on the use of reinforcement with a minimum yield strength of 60,000 pounds per square inch (psi) (414 MPa). Vertical reinforcement with a minimum yield strength of 40,000 psi (276 MPa) or 50,000 psi (345 MPa) shall be permitted, provided that the same size bar is used and the spacing shown in the table is reduced by multiplying the spacing by 0.67 or 0.83, respectively.
3. Vertical reinforcement, where required, shall be placed nearest the inside face of the wall a distance, d, from the outside face (soil face) of the wall. The distance, d, is equal to the wall thickness, t, minus 1.25 inches (32 mm) plus one-half the bar diameter, d b , [ d = t – (1.25 + d b /2)]. The reinforcement shall be placed within a tolerance of ± [3] / 8 inch (9.5 mm) where d is less than or equal to 8 inches (203 mm) or ± [1] / 2 inch (12.7 mm) where d is greater than 8 inches (203 mm).
4. In lieu of the reinforcement shown in Table 1807.1.6.2, smaller reinforcing bar sizes with closer spacings that provide an equivalent cross-sectional area of reinforcement per unit length shall be permitted.
CRC § 4-39 High relevance — show source text
1. In Seismic Design Categories D 0, D 1 and D 2, prescriptive reinforcement shall be provided in the horizontal and vertical direction. Provide minimum horizontal joint reinforcement of two No. 9 gage wires spaced not less than 6 inches (152
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mm) or one [1] / 4 -inch-diameter (6.4 mm) wire at 10 inches (254 mm) on center vertically. Provide minimum vertical reinforcement of one No. 4 bar at 48 inches (1220 mm) on center horizontally grouted in place.

FIGURE R404.1.5.3—FOUNDATION WALL CLAY MASONRY CURTAIN WALL WITH CONCRETE MASONRY PIERS

For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 degree = 0.0175 rad.

R404.1.6 Height above finished grade. Concrete and masonry foundation walls shall extend above the finished grade adjacent to the foundation at all points not less than 4 inches (102 mm) where masonry veneer is used and not less than 6 inches (152 mm) elsewhere.

R404.1.7 Backfill placement. Backfill shall not be placed against the wall until the wall has sufficient strength and has been anchored to the floor above, or has been sufficiently braced to prevent damage by the backfill.

Exception: Bracing is not required for walls supporting less than 4 feet (1219 mm) of unbalanced backfill.

R404.1.8 Rubble stone masonry. Rubble stone masonry foundation walls shall have a minimum thickness of 16 inches (406 mm), shall not support an unbalanced backfill exceeding 8 feet (2438 mm) in height, shall not support a soil pressure greater than 30 pounds per square foot per foot (4.71 kPa/m), and shall not be constructed in Seismic Design Categories D 0, D 1, D 2 or townhouses in Seismic Design Category C, as established in Figure R301.2(2).

R404.1.9 Isolated masonry piers. Isolated masonry piers shall be constructed in accordance with this section and the general masonry construction requirements of Section R606. Hollow masonry piers shall have a minimum nominal thickness of 8 inches (203 mm), with a nominal height not exceeding four times the nominal thickness and a nominal length not exceeding three times the nominal thickness. Where hollow masonry units are solidly filled with concrete or grout, piers shall be permitted to have a nominal height not exceeding ten times the nominal thickness. Footings for isolated masonry piers shall be sized in accordance with Section R403.1.1.

R404.1.9.1 Pier cap. Hollow masonry piers shall be capped with 4 inches (102 mm) of solid masonry or concrete, a masonry cap block, or shall have cavities of the top course filled with concrete or grout. Where required, termite protection for the pier cap shall be provided in accordance with Section R305.

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**R404.1.9.2 Masonry piers supporting floor girders.

CRC § 304.8 High relevance — show source text

4 mm, 1 foot = 304.8 mm, 1 mph = 0.447 m/s.|For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 mph = 0.447 m/s.|For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 mph = 0.447 m/s.|For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 mph = 0.447 m/s.|For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 mph = 0.447 m/s.|

SECTION R404—FOUNDATION AND RETAINING WALLS

R404.1 Concrete and masonry foundation walls. Concrete foundation walls shall be selected and constructed in accordance with the provisions of Section R404.1.3. Masonry foundation walls shall be selected and constructed in accordance with the provisions of Section R404.1.2.

R404.1.1 Design required. Concrete or masonry foundation walls shall be designed in accordance with accepted engineering practice where either of the following conditions exists:

Walls are subject to hydrostatic pressure from ground water.
Walls supporting more than 48 inches (1219 mm) of unbalanced backfill that do not have permanent lateral support at the top or bottom.

R404.1.2 Design of masonry foundation walls. Masonry foundation walls shall be designed and constructed in accordance with the provisions of this section or in accordance with the provisions of TMS 402. Where TMS 402 or the provisions of this section are used to design masonry foundation walls, project drawings, typical details and specifications are not required to bear the seal of the architect or engineer responsible for design, unless otherwise required by the state law of the jurisdiction having authority.

R404.1.2.1 Masonry foundation walls. Concrete masonry and clay masonry foundation walls shall be constructed as set forth in Table R404.1.2.1(1), R404.1.2.1(2), R404.1.2.1(3) or R404.1.2.1(4) and shall comply with applicable provisions of Section R606. In buildings assigned to Seismic Design Categories D 0, D 1 and D 2, concrete masonry and clay masonry foundation walls shall also comply with Section R404.1.4.1. Rubble stone masonry foundation walls shall be constructed in accordance with Sections R404.1.8 and R606.4.2. Rubble stone masonry walls shall not be used in Seismic Design Categories D 0, D 1 and D 2, or in townhouses in Seismic Design Category C.

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TABLE R404.1.2.1(1)—PLAIN MASONRY FOUNDATION WALLSf	Col2	Col3	Col4	Col5
MAXIMUM UNSUPPORTED WALL HEIGHT (feet)	MAXIMUM UNBALANCED BACKFILL HEIGHTc (feet)	PLAIN MASONRYa MINIMUM NOMINAL WALL THICKNESS (inches)	** PLAIN

CRC § 1.5 Medium relevance — show source text
R404.1.5 Foundation wall thickness based on walls supported. The thickness of masonry or concrete foundation walls shall be not less than that required by Section R404.1.5.1 or R404.1.5.2, respectively.

R404.1.5.1 Masonry wall thickness. Masonry foundation walls shall be not less than the thickness of the wall supported, except that masonry foundation walls of not less than 8-inch (203 mm) nominal thickness shall be permitted under brick veneered frame walls and under 10-inch-wide (254 mm) cavity walls where the total height of the wall supported, including gables, is not more than 20 feet (6096 mm), provided that the requirements of Section R404.1.1 are met.

R404.1.5.2 Concrete wall thickness. The thickness of concrete foundation walls shall be equal to or greater than the thickness of the wall in the story above. Concrete foundation walls with corbels, brackets or other projections built into the wall for support of masonry veneer or other purposes are not within the scope of the tables in this section.

Where a concrete foundation wall is reduced in thickness to provide a shelf for the support of masonry veneer, the reduced thickness shall be equal to or greater than the thickness of the wall in the story above. Vertical reinforcement for the foundation wall shall be based on Table R404.1.3.2(8) and located in the wall as required by Section R404.1.3.3.7.2 where that table is used. Vertical reinforcement shall be based on the thickness of the thinner portion of the wall.

Exception: Where the height of the reduced thickness portion measured to the underside of the floor assembly or sill plate above is less than or equal to 24 inches (610 mm) and the reduction in thickness does not exceed 4 inches (102 mm), the vertical reinforcement is permitted to be based on the thicker portion of the wall.

R404.1.5.3 Pier and curtain wall foundations. Use of pier and curtain wall foundations shall be permitted to support lightframe construction not more than two stories in height, provided that the following requirements are met:
1. All load-bearing walls shall be placed on continuous concrete footings placed integrally with the exterior wall footings.
2. The minimum actual thickness of a load-bearing masonry wall shall be not less than 4 inches (102 mm) nominal or 3 [3] / 8 inches (92 mm) actual thickness, and shall be bonded integrally with piers spaced in accordance with Section R606.6.4.
3. Piers shall be constructed in accordance with Sections R606.7 and R606.7.1, and shall be bonded into the load-bearing masonry wall in accordance with Section R606.13.1 or R606.13.1.1.
4. The maximum height of a 4-inch (102 mm) load-bearing masonry foundation wall supporting wood-frame walls and floors shall be not more than 4 feet (1219 mm).
5. Anchorage shall be in accordance with Section R403.1.6, Figure R404.1.5.3, or as specified by engineered design accepted by the building official.
6. The unbalanced fill for 4-inch (102 mm) foundation walls shall not exceed 24 inches (610 mm) for solid masonry or 12 inches (305 mm) for hollow masonry.
7. In Seismic Design Categories D 0, D 1 and D 2, prescriptive reinforcement shall be provided in the horizontal and vertical direction. Provide minimum horizontal joint reinforcement of two No.
CRC § 1.3.2 Medium relevance — show source text
Reinforcement specified in tables in Section R404.1.3.2 is based on Grade 60 steel reinforcement.
b. Bar spacing shall not exceed 48 inches on center and shall be not less than one-half the nominal wall thickness.
c. For Grade 50 steel bars (ASTM A996M, Type R), use spacing for Grade 40 bars or interpolate between Grades 40 and 60.|For SI: 1 inch = 25.4 mm.
a. This table is for use with tables in Section R404.1.3.2 that specify the minimum bar size and maximum spacing of vertical wall reinforcement for foundation walls and above-
grade walls. Reinforcement specified in tables in Section R404.1.3.2 is based on Grade 60 steel reinforcement.
b. Bar spacing shall not exceed 48 inches on center and shall be not less than one-half the nominal wall thickness.
c. For Grade 50 steel bars (ASTM A996M, Type R), use spacing for Grade 40 bars or interpolate between Grades 40 and 60.|

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FOUNDATIONS

R404.1.3.2.1 Concrete foundation stem walls supporting above-grade concrete walls. Foundation stem walls that support above-grade concrete walls shall be designed and constructed in accordance with this section.
1. Stem walls not laterally supported at top. Concrete stem walls that are not monolithic with slabs-on-ground or are not otherwise laterally supported by slabs-on-ground shall comply with this section. Where unbalanced backfill retained by the stem wall is less than or equal to 18 inches (457 mm), the stem wall and above-grade wall it supports shall be provided with vertical reinforcement in accordance with Section R608.6 and Table R608.6(1), R608.6(2) or R608.6(3) for above-grade walls. Where unbalanced backfill retained by the stem wall is greater than 18 inches (457 mm), the stem wall and above-grade wall it supports shall be provided with vertical reinforcement in accordance with Section R608.6 and Table R608.6(1).
2. Stem walls laterally supported at top. Concrete stem walls that are monolithic with slabs-on-ground or are otherwise laterally supported by slabs-on-ground shall be vertically reinforced in accordance with Section R608.6 and Table R608.6(1), R608.6(2) or R608.6(3) for above-grade walls. Where the unbalanced backfill retained by the stem wall is greater than 18 inches (457 mm), the connection between the stem wall and the slab-on-ground, and the portion of the slab-on-ground providing lateral support for the wall shall be designed in accordance with PCA 100 or with accepted engineering practice. Where the unbalanced backfill retained by the stem wall is greater than 18 inches (457 mm), the minimum nominal thickness of the wall shall be 6 inches (152 mm).
R404.1.3.2.2 Concrete foundation stem walls supporting light-frame above-grade walls. Concrete foundation stem walls that support light-frame above-grade walls shall be designed and constructed in accordance with this section.
1. Stem walls not laterally supported at top.
California Residential Code Medium relevance — show source text
3/8″
main reinforcement bars at 57/8″ pitch
with7/8″ concrete cover;3/8″ main rein-
forcement bars at 41/2″ pitch
perpendicular with1/2″ concrete cover;
13′1″ span restrained.|195 psf|4 hrs|||7|1, 7|4| |F/C-4-RC-7|4″|4″ (5025 psi) concrete deck;1/4″ reinforce-
ment bars at 71/2″ pitch with3/4″ cover;3/8″
main reinforcement bars at 33/4″ pitch
perpendicular with1/2″ cover; 13′1″ span
restrained.|140 psf|1 hr
16 min|||7|1, 2|11/4| |F/C-4-RC-8|4″|4″ thick (4905 psi) deck;1/4″ reinforce-
ment bars at 71/2″ pitch with7/8″ cover;3/8″
main reinforcement bars at 33/4″ pitch
perpendicular with1/2″ cover; 13′1″ span
restrained.|100 psf|1 hr
23 min|||7|1, 2|11/3| |F/C-4-RC-9|4″|4″ deep (4370 psi);1/4″ reinforcement bars
at 6″ pitch with3/4″ cover;1/4″ main rein-
forcement bars at 4″ pitch perpendicular
with1/2″ cover; 13′1″ span restrained.|150 psf|2 hrs|||7|1, 3|2| |F/C-4-RC-10|4″|4″ thick (5140 psi) deck;1/4″ reinforce-
ment bars at 71/2″ pitch with7/8″ cover;3/8″
main reinforcement bars at 33/4″ pitch
perpendicular with1/2″ cover; 13′1″ span
restrained.|140 psf|1 hr
16 min|||7|1, 5|11/4| |F/C-4-RC-11|4″|4″ thick (4000 psi) concrete deck;
3″ × 11/2″ × 4 lbs R.S.J.; 2′6″ C.R.S.; flush
with top surface; 4″ × 6″ x 13 SWG mesh
reinforcement 1″ from bottom of slab; 6′6″
span restrained.|150 psf|2 hrs|||7|1, 3|2| |F/C-4-RC-12|4″|4″ deep (2380 psi) concrete deck;
3″ × 11/2″ × 4 lbs R.S.J.; 2′6″ C.R.S.
CRC § 71.4 Medium relevance — show source text
reinforcement: verti-
cal, four5/8″ rebars; horizontal,3/8″ ties at
7″ pitch; cover: 11/2″.|71.4
tons|2 hrs|||7|2, 7|2| |C-11-RC-20|11″|11″ square columns; gravel concrete (4530
psi); reinforcement: vertical, four5/8″
rebars; horizontal,3/8″ ties at 7″ pitch;
cover: 11/2″ with1/2″ plaster.|58.8
tons|2 hrs|||7|2, 3, 9|2| |C-11-RC-21|11″|11″ square columns; gravel concrete (3520
psi); reinforcement: vertical, four5/8″
rebars; horizontal,3/8″ ties at 7″ pitch;
cover: 11/2″.|Vari-
able|1 hr
24 min|||7|1, 8|11/4| |C-11-RC-22|11″|11″ square columns; aggregate concrete
(3710 psi); reinforcement: vertical, four5/8″
rebars; horizontal,3/8″ ties at 7″ pitch;
cover: 11/2″.|58.8
tons|2 hrs|||7|2, 3,
10|2| |C-11-RC-23|11″|11″ square columns; aggregate concrete
(3190 psi); reinforcement: vertical, four5/8″
rebars; horizontal,3/8″ ties at 7″ pitch;
cover: 11/2″.|58.8
tons|2 hrs|||7|2, 3,
10|2| |C-11-RC-24|11″|11″ square columns; aggregate concrete
(4860 psi); reinforcement: vertical, four
5/8″ rebars; horizontal,3/8″ ties at 7″ pitch;
cover: 11/2″.|86.1
tons|1 hr
20 min|||7|1|11/3| |C-11-RC-25|11″|11″ square columns; aggregate concrete
(4850 psi); reinforcement: vertical, four 5/8″
rebars; horizontal,3/8″ ties at 7″ pitch;
cover: 11/2″.|58.8
tons|1 hr
59 min|||7|1|13/4| |C-11-RC-26|11″|11″ square columns; aggregate concrete
(3834 psi); reinforcement: vertical, four 5/8″
rebars; horizontal,5/16″ ties at 41/2″ pitch;
cover: 11/2″.|71.4
tons|53 min|||7|1|3/4|

For SI: 1 inch = 25.4 mm, 1 pound per square inch = 0.00689 MPa, 1 ton = 8.896 kN.
CRC § 304.8 Medium relevance — show source text
4 mm, 1 foot = 304.8 mm.
a. Mortar shall be Type M or S and masonry shall be laid in running bond. Ungrouted hollow masonry units are permitted except where otherwise indicated.
b. Soil classes are in accordance with the Unified Soil Classification System. Refer to Table R401.4.1(2).
c. Unbalanced backfill height is the difference in height between the exterior finish ground level and the lower of the top of the concrete footing that supports the foundation
wall or the interior finish ground level. Where an interior concrete slab-on-grade is provided and is in contact with the interior surface of the foundation wall, measurement of
the unbalanced backfill height from the exterior finish ground level to the top of the interior concrete slab is permitted.
d. Solid indicates solid masonry unit; grout indicates grouted hollow units.
e. Wall construction shall be in accordance with Table R404.1.2.1(2), R404.1.2.1(3) or R404.1.2.1(4), or a design shall be provided.
f. The use of this table shall be prohibited for soil classifications not shown.|For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm.
a. Mortar shall be Type M or S and masonry shall be laid in running bond. Ungrouted hollow masonry units are permitted except where otherwise indicated.
b. Soil classes are in accordance with the Unified Soil Classification System. Refer to Table R401.4.1(2).
c. Unbalanced backfill height is the difference in height between the exterior finish ground level and the lower of the top of the concrete footing that supports the foundation
wall or the interior finish ground level. Where an interior concrete slab-on-grade is provided and is in contact with the interior surface of the foundation wall, measurement of
the unbalanced backfill height from the exterior finish ground level to the top of the interior concrete slab is permitted.
d. Solid indicates solid masonry unit; grout indicates grouted hollow units.
e. Wall construction shall be in accordance with Table R404.1.2.1(2), R404.1.2.1(3) or R404.1.2.1(4), or a design shall be provided.
f. The use of this table shall be prohibited for soil classifications not shown.|For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm.
a. Mortar shall be Type M or S and masonry shall be laid in running bond. Ungrouted hollow masonry units are permitted except where otherwise indicated.
b. Soil classes are in accordance with the Unified Soil Classification System. Refer to Table R401.4.1(2).
c. Unbalanced backfill height is the difference in height between the exterior finish ground level and the lower of the top of the concrete footing that supports the foundation
wall or the interior finish ground level. Where an interior concrete slab-on-grade is provided and is in contact with the interior surface of the foundation wall, measurement of
the unbalanced backfill height from the exterior finish ground level to the top of the interior concrete slab is permitted.
d. Solid indicates solid masonry unit; grout indicates grouted hollow units.
e.
CRC § 4-38 Medium relevance — show source text
4-38 2025 CALIFORNIA RESIDENTIAL CODE

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

FOUNDATIONS

R404.1.3.4 Requirements for Seismic Design Category C. Concrete foundation walls supporting above-grade concrete walls in townhouses assigned to Seismic Design Category C shall comply with ACI 318, ACI 332 or PCA 100 (see Section R404.1.3).

R404.1.4 Seismic Design Category D 0 , D 1 or D 2 .

R404.1.4.1 Masonry foundation walls. In buildings assigned to Seismic Design Category D 0, D 1 or D 2, as established in Table R301.2, masonry foundation walls shall comply with this section. In addition to the requirements of Table R404.1.2.1(1), plain masonry foundation walls shall comply with the following:
1. Wall height shall not exceed 8 feet (2438 mm).
2. Unbalanced backfill height shall not exceed 4 feet (1219 mm).
3. Minimum nominal thickness for plain masonry foundation walls shall be 8 inches (203 mm).
4. Masonry stem walls shall have a minimum vertical reinforcement of one No. 4 (No. 13) bar located not greater than 4 feet (1219 mm) on center in grouted cells. Vertical reinforcement shall be tied to the horizontal reinforcement in the footings.
Foundation walls, supporting more than 4 feet (1219 mm) of unbalanced backfill or exceeding 8 feet (2438 mm) in height shall be constructed in accordance with Table R404.1.2.1(2), R404.1.2.1(3) or R404.1.2.1(4). Masonry foundation walls shall have two No. 4 (No. 13) horizontal bars located in the upper 12 inches (305 mm) of the wall.

R404.1.4.2 Concrete foundation walls. In buildings assigned to Seismic Design Category D 0, D 1 or D 2, as established in Table R301.2, concrete foundation walls that support light-frame walls shall comply with this section, and concrete foundation walls that support above-grade concrete walls shall comply with ACI 318, ACI 332 or PCA 100 (see Section R404.1.3). In addition to the horizontal reinforcement required by Table R404.1.3.2(1), plain concrete walls supporting light-frame walls shall comply with the following:
1. Wall height shall not exceed 8 feet (2438 mm).
2. Unbalanced backfill height shall not exceed 4 feet (1219 mm).
3. Minimum thickness for plain concrete foundation walls shall be 7.5 inches (191 mm) except that 6 inches (152 mm) is permitted where the maximum wall height is 4 feet 6 inches (1372 mm).

Frequently asked questions

What is “unbalanced backfill” and why does it matter?

Unbalanced backfill is the height difference between exterior finish grade and the lower of the top of the footing or interior finish grade/slab. It matters because many plain‑wall allowances are limited by maximum unbalanced backfill heights (commonly 4 ft for plain walls); exceeding that requires reinforced walls or engineered design. See Table notes in § R404.1.2.1.

When can I use a 6‑inch concrete foundation wall?

A 6‑inch nominal concrete stem wall is permitted in prescriptive provisions when the wall is monolithic with slab‑on‑grade and the unbalanced backfill retained by the stem wall is greater than 18 in, per § R404.1.3.2.1 — subject to the other table limits and SDC considerations.

Do I always need an engineer for foundation walls?

No — the CRC allows prescriptive selection from the tables in § R404.1.2.1 (masonry) and § R404.1.3.2 (concrete) when the wall and site conditions fall within the tables’ scope. An engineered design is required when the wall is subject to hydrostatic pressure, supports more than 48 in of unbalanced backfill without lateral support, or when DR (design required) appears in the tables. See § R404.1.1 and the tables.

What reinforcement spacing limits should I watch for?

Maximum vertical bar spacing in the prescriptive concrete tables is typically 48 in on center, and spacing shall not be less than one‑half the nominal wall thickness; Table R404.1.3.2(9) helps adjust spacing for different steel grades. See § R404.1.3 notes.

If I have brick veneer on top of a foundation wall, does that change wall thickness?

Yes — § R404.1.5.1 allows masonry foundation walls of 8‑inch nominal thickness under brick‑veneered frame walls (and other limited cases) provided other conditions in that section are met. Also concrete foundation walls must be at least as thick as the wall above per § R404.1.5.2.

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California Residential Code