CRC · California Residential Code
When is dampproofing acceptable and when is waterproofing required for foundations?
If the soils/conditions are ordinary, concrete and masonry foundation walls that enclose below‑grade spaces are dampproofed from finished grade down to the higher of the top of footing or 6 inches below the basement floor; but if a high water table or severe soil‑water condition is known, the walls must instead be waterproofed to that same vertical extent using one of the methods listed in § R406.2.
Last reviewed: July 6, 2026
What the code requires — 2-4 sentences
In plain English: for concrete and masonry foundation walls that retain earth and enclose interior spaces below grade, the CRC requires dampproofing unless waterproofing is specifically required where a high water table or other severe soil‑water conditions are known to exist. When waterproofing is required, it must extend from finished grade to the higher of the top of the footing or 6 inches (152 mm) below the top of the basement floor and be installed using one of the prescribed methods. The controlling provisions are § R406.1, § R406.2, and the wood‑foundation rules in § R406.3.
The single most important rule: If a high water table or other severe soil‑water condition is known to exist, you must waterproof the below‑grade walls — dampproofing is not sufficient. § R406.2
Requirements in detail
Which walls are covered
- Concrete and masonry walls that retain earth and enclose interior spaces and floors below grade are covered by § R406.1 and § R406.2.
- Wood foundations enclosing habitable or usable below‑grade spaces have separate dampproofing requirements in § R406.3 (sealed panel joints; 6‑mil polyethylene under and to the wall, etc.).
When dampproofing is acceptable
- Dampproofing is the default for concrete and masonry foundation walls unless waterproofing is required by § R406.2. Dampproofing must extend from finished grade down to the higher of the top of the footing or 6 inches (152 mm) below the top of the basement floor. Acceptable dampproofing materials are listed in § R406.1 (bituminous coating, acrylic modified cement at 3 lb/yd², surface-bonding cement per ASTM C887, any material permitted for waterproofing in § R406.2, or other approved methods). § R406.1
When waterproofing is required
- Waterproofing is required where a high water table or other severe soil‑water conditions are known to exist. In those locations, exterior foundation walls that retain earth and enclose below‑grade spaces shall be waterproofed from finished grade to the higher of the top of the footing or 6 inches (152 mm) below top of basement floor, using one of the approved methods listed in § R406.2. Approved methods are enumerated in § R406.2 (two‑ply hot‑mopped felts; 55‑lb roll roofing; 40‑mil polymer‑modified asphalt; 60‑mil flexible polymer cement; 1/8‑inch cement‑based fiber‑reinforced waterproof coating; 60‑mil solvent‑free liquid‑applied synthetic rubber). All membrane joints must be lapped and sealed with a compatible adhesive. § R406.2
Extent (vertical coverage) — critical threshold
- The vertical extent required for both dampproofing and waterproofing is: from finished grade to the higher of:
- Top of the footing, or
- 6 inches (152 mm) below the top of the basement floor.
This language appears in § R406.1 and § R406.2. § R406.1, § R406.2
Wood foundations (special dampproofing details)
- For wood foundations the CRC requires:
- Sealed plywood panel joints (full‑length caulking) — § R406.3.1.
- A 6‑mil polyethylene film applied over the below‑grade portion of exterior foundation walls before backfilling; joints lapped 6 inches (152 mm) and sealed; film bonded at top edge and extending to the bottom of the wood footing plate but not overlapping or extending into the gravel/crushed‑stone footing — § R406.3.2. § R406.3.1, § R406.3.2
Decision table (quick reference)
| Condition / dimension | Required treatment | Minimum extent (vertical) | Typical acceptable methods | Code Reference |
|---|---|---|---|---|
| Normal soil/ordinary conditions — concrete or masonry walls | Dampproofing (default) | From finished grade to the higher of top of footing or 6 in (152 mm) below top of basement floor | Bituminous coating; acrylic modified cement (3 lb/yd²); surface‑bonding cement per ASTM C887; or any material permitted in § R406.2 | § R406.1 |
| Known high water table or severe soil‑water conditions — concrete or masonry walls | Waterproofing required | From finished grade to the higher of top of footing or 6 in (152 mm) below top of basement floor | One of § R406.2 methods (two‑ply hot‑mopped felts; 55‑lb roll roofing; 40‑mil polymer‑modified asphalt; 60‑mil flexible polymer cement; 1/8‑in cement‑based fiber‑reinforced coating; 60‑mil solvent‑free liquid synthetic rubber) | § R406.2 |
| Wood foundations enclosing habitable/usable below‑grade spaces | Dampproofing with sealed joints + polyethylene moisture barrier | Polyethylene film from grade to bottom of wood footing plate (do not overlap into gravel) — joints lapped 6 in (152 mm) | 6‑mil polyethylene; full‑length caulking at panel joints; protective strip at grade | § R406.3, § R406.3.1, § R406.3.2 |
Exceptions & special cases
- ICF walls (insulating concrete form): the CRC exception in § R406.2 prohibits organic‑solvent‑based products (hydrocarbons, chlorinated hydrocarbons, ketones, esters) for ICF with expanded polystyrene; alternative adhesives/coatings are addressed in the same exception. § R406.2 (Exception)
- Masonry parging exception: unit masonry walls need not be parged if a material is approved for direct application to masonry (see exception in § R406.1). § R406.1 (Exception)
- Use of waterproofing as dampproofing: the code explicitly allows applying materials listed for waterproofing in § R406.2 as dampproofing when dampproofing is required (see § R406.1). § R406.1
If you need a numeric definition of “high water table” or a hydrostatic pressure threshold, the CRC text in § R406 does not provide a numeric cutoff — the trigger is phrased as “where a high water table or other severe soil‑water conditions are known to exist.” For numeric design triggers you will want to consult the geotechnical investigation provisions and local jurisdiction practice (see related provisions below); the CRC text in § R406 itself does not give a specific elevation or numeric value.
Common mistakes
- Treating dampproofing and waterproofing as interchangeable — they are not. Where § R406.2 applies (high water table / severe soil‑water), dampproofing is not acceptable. § R406.2
- Failing to extend the membrane to the higher of the two required elevations (top of footing vs 6 in below the basement floor). The code requires the higher elevation be used. § R406.1, § R406.2
- Using organic‑solvent‑based waterproofers on ICF walls despite the exception in § R406.2. § R406.2 (Exception)
- For wood foundations: not lapping/sealing polyethylene joints 6 in (152 mm), not protecting the film at grade, or allowing the film to extend into the gravel footing — these violate § R406.3.2. § R406.3.2
- Poor attention to membrane joint lapping/sealing and adhesive compatibility; § R406.2 mandates lapped and sealed joints with compatible adhesives for membrane systems. § R406.2
Worked example — concrete basement wall
Scenario: basement floor finished elevation = 100.00 ft, top of footing = 95.50 ft (i.e., footing is 4.5 ft below floor). Finished exterior grade at wall = 101.50 ft. A soils report indicates a high water table is present.
Step 1 — determine the vertical target elevation:
- 6 inches below top of basement floor = 100.00 ft − 0.50 ft = 99.50 ft (6 in = 0.5 ft = 152 mm).
- Top of footing = 95.50 ft.
- The higher of the two = 99.50 ft.
Step 2 — code requirement:
- Because a high water table is known, the wall must be waterproofed (not just dampproofed) from finished grade (101.50 ft) down to 99.50 ft. Select one of the approved methods in § R406.2 (for example, a 40‑mil polymer‑modified asphalt or 60‑mil flexible polymer cement membrane) and ensure all membrane laps/joints are lapped and sealed per § R406.2. § R406.2
Related provisions
- § R405 — Foundation drainage requirements (sumps, perforated pipe, gravel layer) — relevant when addressing groundwater and drainage design.
- § R406.1, § R406.2, § R406.3 — Foundation dampproofing and waterproofing (primary controlling sections summarized above).
- Building Code Chapter 18 / § 1805 (CBC) — Dampproofing and waterproofing guidance where hydrostatic pressure conditions are evaluated, and coordination with geotechnical investigation requirements; consult when hydrostatic pressure or groundwater control systems are involved.
- ASTM standards referenced (e.g., ASTM C887, ASTM D449) — see the CRC referenced standards list for material specifications used by the code.
If you want, I can:
- Produce a simple checklist you can use on site to verify compliance with § R406.1–R406.3, or
- Convert the worked example into a one‑page diagram you can give the contractor showing the elevations to be covered and the permitted material choices.
Code references
Grounded in the retrieved California Residential Code — click a citation to read the verbatim passage:
CRC § 1.5 High relevance — show source text
Exception: Parging of unit masonry walls is not required where a material is approved for direct application to the masonry.
Concrete walls shall be dampproofed by applying any one of the listed dampproofing materials or any one of the waterproofing materials listed in Section R406.2 to the exterior of the wall.
R406.2 Concrete and masonry foundation waterproofing. In areas where a high water table or other severe soil-water conditions are known to exist, exterior foundation walls that retain earth and enclose interior spaces and floors below grade shall be waterproofed from the finished grade to the higher of the top of the footing or 6 inches (152 mm) below the top of the basement floor. Walls shall be waterproofed in accordance with one of the following:
- Two-ply hot-mopped felts.
- Fifty-five-pound (25 kg) roll roofing.
- Forty-mil (1 mm) polymer-modified asphalt.
- Sixty-mil (1.5 mm) flexible polymer cement.
- One-eighth-inch (3 mm) cement-based, fiber-reinforced, waterproof coating.
- Sixty-mil (1.5 mm) solvent-free liquid-applied synthetic rubber.
All joints in membrane waterproofing shall be lapped and sealed with an adhesive compatible with the membrane.
Exception: Organic-solvent-based products such as hydrocarbons, chlorinated hydrocarbons, ketones and esters shall not be used for ICF walls with expanded polystyrene form material. Use of plastic roofing cements, acrylic coatings, latex coatings, mortars and pargings to seal ICF walls is permitted. Cold-setting asphalt or hot asphalt shall conform to Type C of ASTM D449. Hot asphalt shall be applied at a temperature of less than 200°F (93°C).
R406.3 Dampproofing for wood foundations. Wood foundations enclosing habitable or usable spaces located below grade shall be dampproofed in accordance with Sections R406.3.1 through R406.3.4.
R406.3.1 Panel joint sealed. Plywood panel joints in the foundation walls shall be sealed full length with a caulking compound capable of producing a moistureproof seal under the conditions of temperature and moisture content at which it will be applied and used.
R406.3.2 Below-grade moisture barrier. A 6-mil-thick (0.15 mm) polyethylene film shall be applied over the below-grade portion of exterior foundation walls prior to backfilling. Joints in the polyethylene film shall be lapped 6 inches (152 mm) and sealed with adhesive. The top edge of the polyethylene film shall be bonded to the sheathing to form a seal. Film areas at grade level shall be protected from mechanical damage and exposure by a pressure-preservative treated lumber or plywood strip attached to the wall several inches above finished grade level and extending approximately 9 inches (229 mm) below grade. The joint between the strip and the wall shall be caulked full length prior to fastening the strip to the wall. Where approved, other coverings appropriate to the architectural treatment shall be permitted to be used. The polyethylene film shall extend down to the bottom of the wood footing plate but shall not overlap or extend into the gravel or crushed stone footing.
CRC § 2.3 High relevance — show source text
R405.2.3 Drainage system. In other than Group I soils, a sump shall be provided to drain the porous layer and footings. The sump shall be not less than 24 inches (610 mm) in diameter or 20 inches square (0.0129 m [2] ), shall extend not less than 24 inches (610
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mm) below the bottom of the basement floor and shall be capable of positive gravity or mechanical drainage to remove any accumulated water. The drainage system shall discharge into an approved sewer system or to daylight.
SECTION R406 —FOUNDATION WATERPROOFING AND DAMPPROOFING
R406.1 Concrete and masonry foundation dampproofing. Except where required by Section R406.2 to be waterproofed, foundation walls that retain earth and enclose interior spaces and floors below grade shall be dampproofed from the finished grade to the
higher of the top of the footing or 6 inches (152 mm) below the top of the basement floor. Masonry walls shall have not less than [3] / 8inch (9.5 mm) Portland cement parging applied to the exterior of the wall. The parging shall be dampproofed in accordance with one of the following:
- Bituminous coating.
- Three pounds per square yard (1.63 kg/m [2] ) of acrylic modified cement.
- One-eighth-inch (3.2 mm) coat of surface-bonding cement complying with ASTM C887.
- Any material permitted for waterproofing in Section R406.2.
- Other approved methods or materials.
Exception: Parging of unit masonry walls is not required where a material is approved for direct application to the masonry.
Concrete walls shall be dampproofed by applying any one of the listed dampproofing materials or any one of the waterproofing materials listed in Section R406.2 to the exterior of the wall.
R406.2 Concrete and masonry foundation waterproofing. In areas where a high water table or other severe soil-water conditions are known to exist, exterior foundation walls that retain earth and enclose interior spaces and floors below grade shall be waterproofed from the finished grade to the higher of the top of the footing or 6 inches (152 mm) below the top of the basement floor. Walls shall be waterproofed in accordance with one of the following:
- Two-ply hot-mopped felts.
- Fifty-five-pound (25 kg) roll roofing.
- Forty-mil (1 mm) polymer-modified asphalt.
- Sixty-mil (1.5 mm) flexible polymer cement.
- One-eighth-inch (3 mm) cement-based, fiber-reinforced, waterproof coating.
- Sixty-mil (1.5 mm) solvent-free liquid-applied synthetic rubber.
All joints in membrane waterproofing shall be lapped and sealed with an adhesive compatible with the membrane.
Exception: Organic-solvent-based products such as hydrocarbons, chlorinated hydrocarbons, ketones and esters shall not be used for ICF walls with expanded polystyrene form material. Use of plastic roofing cements, acrylic coatings, latex coatings, mortars and pargings to seal ICF walls is permitted. Cold-setting asphalt or hot asphalt shall conform to Type C of ASTM D449. Hot asphalt shall be applied at a temperature of less than 200°F (93°C).
CRC § 3-82 High relevance — show source text
R336 Large Family Day-Care Homes . . . . . . . . . . . . . . . . . . . 3-82
R337 Materials and Construction Methods for Exterior
Wildfire Exposure . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-83
R338 Electric Vehicle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-83
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R339 Reserved . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-84
R340 Pollutant Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-84
CHAPTER 4 FOUNDATIONS . . . . . . . . . . . . . . . . . . . . . . . . . 4-3
R401 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3
R402 Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5
R403 Footings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-6
R404 Foundation and Retaining Walls . . . . . . . . . . . . . . . . 4-24
R405 Foundation Drainage . . . . . . . . . . . . . . . . . . . . . . . . . . 4-42
R406 Foundation Waterproofing and Dampproofing . . . 4-43
R407 Columns. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-44
R408 Under-Floor Space . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-44
CHAPTER 5 FLOORS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3
R501 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3
R502 Wood Floor Framing . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3
R503 Floor Sheathing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-12
R504 Pressure Preservative-Treated Wood
CRC § 4.1 Medium relevance — show source text
Drainage tiles or perforated pipe shall be placed on not less than 2 inches (51 mm) of washed gravel or crushed rock not less than one sieve size larger than the tile joint opening or perforation and covered with not less than 6 inches (152 mm) of the same material.
Exception: A drainage system is not required where the foundation is installed on well-drained ground or sand-gravel mixture soils according to the Unified Soil Classification System, Group I soils, as detailed in Table R401.4.1(2).
R405.1.1 Precast concrete foundation. Precast concrete walls that retain earth and enclose habitable or useable space located below-grade that rest on crushed stone footings shall have a perforated drainage pipe installed below the base of the wall on either the interior or exterior side of the wall, not less than 1 foot (305 mm) beyond the edge of the wall. If the exterior drainage pipe is used, an approved filter membrane material shall cover the pipe. The drainage system shall discharge into an approved sewer system or to daylight.
R405.2 Wood foundations. Wood foundations enclosing habitable or usable spaces located below grade shall be adequately drained in accordance with Sections R405.2.1 through R405.2.3.
R405.2.1 Base. A porous layer of gravel, crushed stone or coarse sand shall be placed to a minimum thickness of 4 inches (102 mm) under the basement floor. Provision shall be made for automatic draining of this layer and the gravel or crushed stone wall footings.
R405.2.2 Vapor retarder. A 6-mil-thick (0.15 mm) polyethylene vapor retarder shall be applied over the porous layer with the basement floor constructed over the polyethylene.
R405.2.3 Drainage system. In other than Group I soils, a sump shall be provided to drain the porous layer and footings. The sump shall be not less than 24 inches (610 mm) in diameter or 20 inches square (0.0129 m [2] ), shall extend not less than 24 inches (610
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mm) below the bottom of the basement floor and shall be capable of positive gravity or mechanical drainage to remove any accumulated water. The drainage system shall discharge into an approved sewer system or to daylight.
SECTION R406 —FOUNDATION WATERPROOFING AND DAMPPROOFING
R406.1 Concrete and masonry foundation dampproofing. Except where required by Section R406.2 to be waterproofed, foundation walls that retain earth and enclose interior spaces and floors below grade shall be dampproofed from the finished grade to the
higher of the top of the footing or 6 inches (152 mm) below the top of the basement floor. Masonry walls shall have not less than [3] / 8inch (9.5 mm) Portland cement parging applied to the exterior of the wall. The parging shall be dampproofed in accordance with one of the following:
- Bituminous coating.
- Three pounds per square yard (1.63 kg/m [2] ) of acrylic modified cement.
- One-eighth-inch (3.2 mm) coat of surface-bonding cement complying with ASTM C887.
- Any material permitted for waterproofing in Section R406.2.
- Other approved methods or materials.
CRC § 17A-4 Medium relevance — show source text
1704A Special Inspections and Tests, Contractor Responsibility and Structural Observation . . . . . . . . . . . . . . . . . . .17A-4
1705A Required Special Inspections and Tests . . . . . . . . . .17A-6
1706A Design Strengths of Materials . . . . . . . . . . . . . . . . . .17A-22
1707A Alternative Test Procedure . . . . . . . . . . . . . . . . . . . . .17A-22
1708A In-Situ Load Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17A-22
1709A Preconstruction Load Tests . . . . . . . . . . . . . . . . . . . .17A-22
1710A Off-Site Construction [OSHPD 1 & 4] . . . . . . . . . . . . .17A-23
CHAPTER 18 SOILS AND FOUNDATIONS. . . . . . . . . . . . . . 18-1
1801 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-3
1802 Design Basis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-3
1803 Geotechnical Investigations. . . . . . . . . . . . . . . . . . . . 18-3
1804 Excavation, Grading and Fill. . . . . . . . . . . . . . . . . . . . 18-7
1805 Dampproofing and Waterproofing . . . . . . . . . . . . . . 18-7
1806 Presumptive Load-Bearing Values of Soils . . . . . . . 18-9
1807 Foundation Walls, Retaining Walls and Embedded Posts and Poles . . . . . . . . . . . . . . . . . 18-10
1808 Foundations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-16
1809 Shallow Foundations . . . . . . . . . . . . . . . . . . . . . . . . . 18-18
1810 Deep Foundations. . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-20
1811 Prestressed Rock and Soil Foundation
Anchors [OSHPD 1R, 2 & 5]. . . . . . . . . . . . . . . . . . . . . 18-31
1812 Earth Retaining Shoring
[OSHPD 1R, 2 & 5] . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18-32
1813 Vibro Stone Columns for Ground Improvement
CRC § 0.006 Medium relevance — show source text
Where installed beneath the slab, dampproofing shall consist of not less than 6-mil (0.006 inch; 0.152 mm) polyethylene with joints lapped not less than 6 inches (152 mm), or other approved methods or materials. Where permitted to be installed on top of the slab, dampproofing shall consist of mopped-on bitumen, not less than 4-mil (0.004 inch; 0.102 mm) polyethylene, or other approved methods or materials. Joints in the membrane shall be lapped and sealed in accordance with the manufacturer’s installation instructions.
1805.2.2 Walls. Dampproofing materials for walls shall be installed on the exterior surface of the wall, and shall extend from the top of the footing to above ground level. Dampproofing shall consist of a bituminous material, 3 pounds per square yard (16 N/m [2] ) of acrylic modified cement, [1] / 8 inch (3.2 mm) coat of surface-bonding mortar complying with ASTM C887, any of the materials permitted for waterproofing by Section 1805.3.2 or other approved methods or materials.
1805.2.2.1 Surface preparation of walls. Prior to application of dampproofing materials on concrete walls, holes and recesses resulting from the removal of form ties shall be sealed with a bituminous material or other approved methods or materials. Unit masonry walls shall be parged on the exterior surface below ground level with not less than [3] / 8 inch (9.5 mm) of Portland cement mortar. The parging shall be coved at the footing.
Exception: Parging of unit masonry walls is not required where a material is approved for direct application to the masonry.
1805.3 Waterproofing. Where the ground-water investigation required by Section 1803.5.4 indicates that a hydrostatic pressure condition exists, and the design does not include a ground-water control system as described in Section 1805.1.3, walls and floors shall be waterproofed in accordance with this section.
1805.3.1 Floors. Floors required to be waterproofed shall be of concrete and designed and constructed to withstand the hydrostatic pressures to which the floors will be subjected.
Waterproofing shall be accomplished by placing a membrane of rubberized asphalt, butyl rubber, fully adhered/fully bonded HDPE or polyolefin composite membrane or not less than 6-mil [0.006 inch (0.152 mm)] polyvinyl chloride with joints lapped not less than 6 inches (152 mm) or other approved materials under the slab. Joints in the membrane shall be lapped and sealed in accordance with the manufacturer’s installation instructions.
1805.3.2 Walls. Walls required to be waterproofed shall be of concrete or masonry and shall be designed and constructed to withstand the hydrostatic pressures and other lateral loads to which the walls will be subjected.
CRC § 2.5 Medium relevance — show source text
Parapet construction R302.2.5 Scope R101.2 Separation R302.2 Structural independence R302.2.6 Trusses
Steel R505.1.3, R804.3.6 Wood R502.12, R802.10 Tubular Daylighting Device (TDD) (see Skylights) Two-Family Dwellings R302.3
Under Floor
Space R408
Vapor Retarders R702.7 Capillary break R506.2.3.1 Under floor R408.8 Vehicular Gates Appendix BH Veneer
Masonry R703.7 Ventilation Adjoining rooms R325.1.3 Bathroom and kitchen R325.2
Habitable rooms R325.1
Roof R806
Under floor R408.1 Venting (Mechanical) Chimney and vent connectors R1006 Fireplace R1006 General R325.3
Violations R113 Visible Transmittance (VT)
Wall Furnace (see Appliance) Wallboard (see Gypsum) Walls
Bathtub compartments R327.2 Bracing, steel R603.9 Bracing, wood R602.10 Construction Chapter 6 Covering Chapter 7 Crawl space R202 Cripple R602.9
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INDEX
Deflection R301.7
Exterior, defined R202 Exterior covering R703 Finishes R327.2, R702 Fireplace R1001.5 Foundation R404 Insulating concrete form R608.3, R608.4, R608.5.3 Steel framing R603 Structural insulated panels (SIP) R610 Thickness, masonry chimneys R1003.10 Wood framing R602 Waste
Construction waste R334
Water Closet R326.1, R327 Clearances for R327.1 Waterproofing And dampproofing R406 Wells (see Individual Water Supply) Whirlpool Bathtubs R324.3.1, P2720 Wind
Design criteria R301.2, R301.2.1 Speed maps Figure R301.2(2) Window R609 Emergency Escape and Rescue Openings R319, R321.2.2 Fall protection R321.2 Glazing R324 Light and ventilation R325 Opening limiting devices R321.2.2 Wood
Floor construction R502
Foundation walls R404.2 Protection against decay R304 Roof-ceiling construction R802 Shakes R905.8 Shingles R905.7 Trusses R502.12, R802.10 Walls R602
Yard R318.1, R319.1, R319.2.4, R325.1.1
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HISTORY NOTE APPENDIX
CRC § 4-6 Medium relevance — show source text
R403 Footings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-6
R404 Foundation and Retaining Walls . . . . . . . . . . . . . . . . 4-24
R405 Foundation Drainage . . . . . . . . . . . . . . . . . . . . . . . . . . 4-42
R406 Foundation Waterproofing and Dampproofing . . . 4-43
R407 Columns. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-44
R408 Under-Floor Space . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-44
CHAPTER 5 FLOORS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3
R501 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3
R502 Wood Floor Framing . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3
R503 Floor Sheathing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-12
R504 Pressure Preservative-Treated Wood
Floors (On Ground) . . . . . . . . . . . . . . . . . . . . . . . . . . 5-14
R505 Cold-Formed Steel Floor Framing . . . . . . . . . . . . . . . 5-14
R506 Concrete Floors (On Ground) . . . . . . . . . . . . . . . . . . . 5-26
R507 Exterior Decks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-26
CHAPTER 6 WALL CONSTRUCTION. . . . . . . . . . . . . . . . . . . 6-3
R601 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3
R602 Wood Wall Framing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3
R603 Cold-Formed Steel Wall Framing. . . . . . . . . . . . . . . . 6-53
R604 Wood Structural Panels . . . . . . . . . . . . . . . . . . . . . . . . 6-93
R605 Particleboard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-93
R606 General Masonry Construction. . . . . . . . . . . . . . . . . . 6-93
CRC § 25.4 Medium relevance — show source text
|17′-7″| |800S162-68|12′-10″|11′-6″|18′-6″|16′-7″|19′-11″|18′-11″| |1000S162-43|—|—|—|—|—|—| |1000S162-54|12′-10″|11′-7″|18′-5″|16′-6″|19′-8″|18′-8″| |1000S162-68|13′-8″|12′-3″|19′-8″|17′-9″|21′-1″|20′-1″| |1200S162-43|—|—|—|—|—|—| |1200S162-54|—|—|—|—|—|—| |1200S162-68|14′-5″|12′-11″|20′-9″|18′-7″|22′-0″|21′-0″| |For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 mil = 0.0254 mm, 1 pound per square foot = 0.0479 kPa.
a. Deflection criterion:L/240 for total loads.
b. Ceiling deal load = 5 psf.
c. Minimum Grade 33 ksi steel shall be used for 33 mil and 43 mil thicknesses. Minimum Grade 50 ksi steel shall be used for 54 and 68 mil thicknesses.
d. Listed allowable spans are not applicable for 350S162-33, 350S162-43, 550S162-33, 550S162-43 and 800S162-43 continuous joist members.|For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 mil = 0.0254 mm, 1 pound per square foot = 0.0479 kPa.
a. Deflection criterion:L/240 for total loads.
b. Ceiling deal load = 5 psf.
c. Minimum Grade 33 ksi steel shall be used for 33 mil and 43 mil thicknesses. Minimum Grade 50 ksi steel shall be used for 54 and 68 mil thicknesses.
d. Listed allowable spans are not applicable for 350S162-33, 350S162-43, 550S162-33, 550S162-43 and 800S162-43 continuous joist members.|For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 mil = 0.0254 mm, 1 pound per square foot = 0.0479 kPa.
a. Deflection criterion:L/240 for total loads.
b. Ceiling deal load = 5 psf.
c. Minimum Grade 33 ksi steel shall be used for 33 mil and 43 mil thicknesses. Minimum Grade 50 ksi steel shall be used for 54 and 68 mil thicknesses.
d.CRC § 2.5 Medium relevance — show source text
R606.2.5
C1396/C1396M—2017: Specification for Gypsum Board Table R602.3(1), R702.2.1, R702.2.2, R702.3.1, R702.3.7
C1405—20a: Standard Specification for Glazed Brick (Single Fired, Brick Units)
R606.2.2
C1492—2003(2016): Specification for Concrete Roof Tile
R905.3.5
C1513—2018: Standard Specification for Steel Tapping Screws for Cold-Formed Steel Framing Connections R505.2.5, R603.2.5, R702.3.5.1, Table R703.3(2), Table R703.16.1, Table R703.16.2, R804.2.5
C1634—20: Standard Specification for Concrete Facing Brick and Other Concrete Masonry Facing Units
R606.2.1
C1658/C1658M—19e1: Standard Specification for Glass Mat Gypsum Panels
R702.3.1
C1670/1670M—21b: Standard Specification for Adhered Manufactured Stone Masonry Veneer Units
R606.2.6
C1691—2021: Standard Specification for Unreinforced Autoclaved Aerated Concrete (AAC) Masonry Units
R606.2.3
C1693—2011(2017): Standard Specification for Autoclaved Aerated Concrete (AAC)
R606.2.3
C1766—2015(2019): Standard Specification for Factory-Laminated Gypsum Panel Products
R702.3.1
C1902—20: Standard Specification for Cellular Glass Insulation Used in Building and Roof Applications
Table R906.2
D41/D41M—2011(2016): Specification for Asphalt Primer Used in Roofing, Dampproofing and Waterproofing Table R905.9.2, Table R905.11.2
D43/D43M—2000(2018): Specification for Coal Tar Primer Used in Roofing, Dampproofing and Waterproofing
Table R905.9.2
D226/D226M—2017: Specification for Asphalt-Saturated Organic Felt Used in Roofing and Waterproofing R703.2, R905.1.1, Table R905.1.1(1), R905.8.4, Table R905.9.2
D227/D227M—2003(2018): Specification for Coal-Tar-Saturated Organic Felt Used in Roofing and Waterproofing
Table R905.9.2
D312/D312M—2016a: Specification for Asphalt Used in Roofing
Table R905.9.2
D422—63(2007)E2: Test Method for Particle-Size Analysis of Soils
R403.1.8.1
D449/D449M—03(2021): Specification for Asphalt Used in Dampproofing and Waterproofing
R406.2
2025 CALIFORNIA RESIDENTIAL CODE 44-9
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
REFERENCED STANDARDS
D450/D450M—2017(2018): Specification for Coal-Tar Pitch Used in Roofing, Dampproofing and Waterproofing
Table R905.9.2
CRC § 2-1000 Medium relevance — show source text
000S162-54|5′-0″|4′-4″|3′-6″|2′-9″|—|4′-11″|4′-3″|3′-5″|2′-7″|—| |2-1000S162-68|6′-10″|6′-0″|5′-3″|4′-6″|3′-10″|6′-9″|5′-11″|5′-2″|4′-5″|3′-9″| |2-1200S162-54|4′-2″|3′-7″|3′-3″|2′-11″|—|4′-1″|3′-7″|3′-2″|2′-10″|—| |2-1200S162-68|7′-7″|6′-7″|5′-9″|5′-0″|4′-2″|7′-6″|6′-6″|5′-8″|4′-10″|4′-1″| |For SI: 1 mil = 0.0254 mm, 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kPa, 1 pound per square inch = 6.895 kPa, 1 ksi = 1,000 psi = 6.895 MPa.
a. Deflection criteria:L/360 for live loads,L/240 for total loads.
b. Design load assumptions:
Second-floor dead load is 10 psf.
Roof/ceiling dead load is 12 psf.
Second-floor live load is 40 psf.
Third floor live load is 30 psf.
Attic live load is 10 psf.
c. Building width is in the direction of horizontal framing members supported by the header.
d. Minimum Grade 33 ksi steel shall be used for 33 mil and 43 mil thicknesses. Minimum Grade 50 ksi steel shall be used for 54 and 68 mil thicknesses.|For SI: 1 mil = 0.0254 mm, 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kPa, 1 pound per square inch = 6.895 kPa, 1 ksi = 1,000 psi = 6.895 MPa.
a. Deflection criteria:L/360 for live loads,L/240 for total loads.
b. Design load assumptions:
Second-floor dead load is 10 psf.
Roof/ceiling dead load is 12 psf.
Second-floor live load is 40 psf.
Third floor live load is 30 psf.
Attic live load is 10 psf.
c. Building width is in the direction of horizontal framing members supported by the header.
d. Minimum Grade 33 ksi steel shall be used for 33 mil and 43 mil thicknesses.CRC § 2-1200 Medium relevance — show source text
-4″|5′-11″|5′-1″|4′-5″|3′-8″|2′-11″| |2-1200S162-54|3′-11″|3′-5″|3′-0″|2′-4″|—|3′-7″|3′-2″|2′-10″|—|—| |2-1200S162-68|7′-1″|6′-2″|5′-3″|4′-6″|3′-8″|6′-6″|5′-8″|4′-10″|4′-0″|3′-3″| |For SI: 1 mil = 0.0254 mm, 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kPa, 1 pound per square inch = 6.895 kPa, 1 ksi = 1,000 psi = 6.895 MPa.
a. Deflection criteria:L/360 for live loads,L/240 for total loads.
b. Design load assumptions:
Second-floor dead load is 10 psf.
Roof/ceiling dead load is 12 psf.
Second-floor live load is 40 psf.
Third floor live load is 30 psf.
Attic live load is 10 psf.
c. Building width is in the direction of horizontal framing members supported by the header.
d. Minimum Grade 33 ksi steel shall be used for 33 mil and 43 mil thicknesses. Minimum Grade 50 ksi steel shall be used for 54 and 68 mil thicknesses.|For SI: 1 mil = 0.0254 mm, 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kPa, 1 pound per square inch = 6.895 kPa, 1 ksi = 1,000 psi = 6.895 MPa.
a. Deflection criteria:L/360 for live loads,L/240 for total loads.
b. Design load assumptions:
Second-floor dead load is 10 psf.
Roof/ceiling dead load is 12 psf.
Second-floor live load is 40 psf.
Third floor live load is 30 psf.
Attic live load is 10 psf.
c. Building width is in the direction of horizontal framing members supported by the header.
d. Minimum Grade 33 ksi steel shall be used for 33 mil and 43 mil thicknesses. Minimum Grade 50 ksi steel shall be used for 54 and 68 mil thicknesses.|For SI: 1 mil = 0.0254 mm, 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kPa, 1 pound per square inch = 6.895 kPa, 1 ksi = 1,000 psi = 6.895 MPa.
a. Deflection criteria:L/360 for live loads,L/240 for total loads.
b.
Frequently asked questions
When does the code actually force waterproofing instead of dampproofing?
When a high water table or other severe soil‑water conditions are known to exist the CRC requires waterproofing rather than dampproofing; this requirement is in § R406.2.
How far down must the dampproofing or waterproofing go?
Both dampproofing and waterproofing must extend from finished grade to the higher of the top of the footing or 6 inches (152 mm) below the top of the basement floor, per § R406.1/§ R406.2.
May I use a waterproofing membrane as dampproofing?
Yes. § R406.1 explicitly allows use of any material permitted for waterproofing in § R406.2 when dampproofing is required.
Are there special requirements for wood foundations?
Yes. Wood foundations require sealed panel joints and a 6‑mil polyethylene below‑grade moisture barrier with 6‑inch laps, bonded at the top edge and extending to the bottom of the wood footing plate (do not overlap into the gravel) — § R406.3.1 and § R406.3.2.
What if my soils report says hydrostatic pressure exists?
If hydrostatic pressure is indicated by geotechnical investigation, waterproofing and/or specific groundwater control measures are required; consult the Building Code Chapter 18 provisions (e.g., § 1805) and coordinate with § R406.2. The CRC text in § R406 itself uses the “high water table / severe soil‑water” trigger but does not provide a numeric water table elevation.
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