CRC · California Residential Code
Exterior decks: attachment, ledger and safety requirements
Your deck ledger must be a minimum 2x8 pressure‑treated member fastened to a code‑grade band joist with the fastener type, spacing and edge distances shown in § R507.9.1.3, flashed and lapped with the WRB per §§ R507.9.1.5–.6, and the deck must include hold‑downs and guard connections that provide a continuous load path for lateral and guard loads per §§ R507.9.2 and R507.10.
Last reviewed: July 6, 2026
What the code requires — 2-4 sentences
Exterior decks attached to a house must be positively anchored to the primary structure for both vertical and lateral loads and may not be held only with toenails or nails subject to withdrawal (see § R507.8). Vertical load transfer to an exterior wall is required to use a properly sized ledger or an approved alternate; ledgers have minimum material, fastening, flashing and water‑resistive barrier requirements (see § R507.9 and subsections). Lateral connections (hold‑downs or equivalent) and guard attachment must provide a continuous load path into the deck framing and the ground (see § R507.9.2 and § R507.10).
The single most important rule: a deck attached to a wall must be anchored to resist both vertical and lateral loads using the ledger, fasteners, flashing and hold‑down details required by § R507 — do not rely on toenails or unsupported connections.
Requirements in detail
Ledger sizing and materials
- Ledger: minimum 2‑inch by 8‑inch nominal (2x8), No. 2 grade or better pressure‑preservative‑treated Southern pine, incised pressure‑treated hem‑fir, or naturally durable/decay‑resistant wood. § R507.9.1.1.
- Band joist supporting a ledger: minimum 2‑inch nominal solid‑sawn SPF (or 1‑inch nominal engineered rim board per § R502.1.7). Band joists must bear fully on the primary structure. § R507.9.1.2.
Ledger-to-band‑joist fasteners and placement
- Ledgers must be fastened in accordance with Table R507.9.1.3(1) and installed per Table R507.9.1.3(2) and Figures R507.9.1.3(1)/(2). Holes for 1/2‑inch lag screws must be predrilled through the ledger/sheathing and a smaller pilot hole through the band joist as required. § R507.9.1.3.
Key minimum edge/end distances and row spacing (Table R507.9.1.3(2)):
| Item | Minimum top edge | Minimum bottom edge | Minimum ends | Row spacing | Code Reference |
|---|---|---|---|---|---|
| Ledger (ledgera) | 2 inches | 3/4 inch | 2 inches | 1 5/8 inches | § R507.9.1.3 |
| Band joist (band joistc) | 3/4 inch | 2 inches | 2 inches | 1 5/8 inches | § R507.9.1.3 |
Notes in the code allow reduction of some spacings (for example, spacing can be reduced to 4.5 inches for lag screws attaching a 2x8 ledger to a 2x8 band joist) when the figure/notes permit — follow Figure R507.9.1.3(1) and the table notes. § R507.9.1.3.
Flashing and water‑resistive barrier (WRB)
- Where ledgers attach to wood‑frame construction, install ledger flashing that extends not less than 2 inches vertically above the ledger and not less than 4 inches horizontally beyond the ledger face (or to ledger face and 1/4 inch down the ledger face). § R507.9.1.5.
- The water‑resistive barrier required by § R703.2 must be lapped over a vertical leg of the ledger flashing by not less than 2 inches (or the height of the vertical flashing leg, whichever is less) and continue behind the ledger flashing/ledger. § R507.9.1.6.
- For existing walls lacking WRB, the code prescribes installing WRB and counterflashing details before attaching a ledger. § R507.9.1.7.
Lateral load connections (hold‑downs)
- Lateral loads must be transferred to ground or to a structure capable of transmitting them. If using the Figure R507.9.2(1) detail, install hold‑down tension devices in at least two locations per deck, each with an allowable stress design capacity of not less than 1,500 pounds, and installed within 24 inches of each end. § R507.9.2.
- The alternate Figure R507.9.2(2) detail requires at least four hold‑down devices, each with 750 pounds capacity, evenly distributed with one within 24 inches of each end. Figures show lag screws/bolts staggered and required joist hanger/connection details. § R507.9.2.
Joist bearing, restraint and decking attachment
- Joist bearing: minimum 1 1/2 inches bearing on wood/metal and 3 inches on concrete/masonry. Joists bearing on top of a single‑ply beam/ledger must use a mechanical connector; joists framed into the side must use approved joist hangers. § R507.6.1.
- Joist lateral restraint: blocking depth must be at least 60% of joist depth (or secure rim to each joist with three 10d nails or three No.10 x 3" screws). § R507.6.2.
- Decking attachment (wood): attach to each supporting member with not less than two 8d deformed‑shank nails or two No.8 wood screws; max allowable joist spacing for wood decking is in Table R507.7. § R507.7.
Exterior guards and guard attachment
- Guards must be constructed to meet § R301.5 and § R321 and be attached so loads are transferred to deck joists through a continuous load path. § R507.10.
- If guards are connected to the interior or exterior side of a joist or beam, that joist/beam must be connected to adjacent joists to prevent rotation; connections that rely only on end‑grain withdrawal fasteners are prohibited. § R507.10.1.1.
- Where 4x4 wood posts support guard loads applied to the top of the guard, they shall not be notched at the supporting connection. § R507.10.2.
Exceptions & special cases
- Where positive connection to the primary structure cannot be verified during inspection, decks must be self‑supporting (i.e., supported on independent posts/footings) — § R507.8.
- Alternate framing configurations that meet the load requirements of § R301.5 are permitted in lieu of prescriptive ledger details — see § R507.9.1.4 (use engineering).
- Flashing exceptions: flashing may be omitted when the ledger is spaced horizontally from the exterior wall covering not less than 1/4 inch to allow drainage/ventilation, or where specific window/door proximity conditions exist — see exceptions in § R507.9.1.5 and § R507.9.1.7.
- Engineered rim joists: the manufacturer’s recommendations govern fastener spacing and details for engineered rim joists in place of the prescriptive Table R507.9.1.3 values. § R507.9.1.3.
Common mistakes
- Relying on toenails or face nails that are subject to withdrawal to attach a ledger — the code explicitly prohibits this for ledger attachment. § R507.8.
- Omitting flashing or WRB laps and allowing water to contact the band‑joist, which causes decay and ledger failure. Follow § R507.9.1.5–.7.
- Using undersized ledgers or attaching a ledger to unsupported finishes (for example, stone or masonry veneer is not an acceptable support). § R507.9.1.1.
- Failing to provide required lateral connections (hold‑downs) or installing insufficient capacity devices or incorrect spacing — check § R507.9.2 and associated figures.
- Attaching guards directly to decking without a continuous load path into the framing (or not securing posts per § R507.10). § R507.10.
Worked example — ledger attachment for a typical 2x8 ledger to a 2x8 band joist
Scenario: Attach a 2x8 ledger to a 2x8 band joist on a wood‑frame house (no engineered rim), deck runs continuous along the wall.
Steps that meet the prescriptive code details:
- Use a 2‑inch by 8‑inch nominal pressure‑treated ledger (No.2 or better) and confirm the band joist is 2‑inch nominal solid‑sawn and bears on the primary structure. § R507.9.1.1–.2.
- Fasteners: follow Table R507.9.1.3(1) for required fastener type and spacing (for 2x8-to-2x8, the notes permit lag‑screw spacing as close as 4.5 inches o.c. when the figure/table notes permit). Stagger the fasteners in two rows per Figure R507.9.1.3(1). Predrill the ledger/sheathing and band joist per the predrill instructions for 1/2‑inch lag screws in § R507.9.1.3.
- Maintain the minimum distances from edges and ends: top edge 2 inches, bottom edge 3/4 inch, ends 2 inches, and row spacing 1 5/8 inches, as required by Table R507.9.1.3(2). § R507.9.1.3.
- Install ledger flashing extending 2 inches up the wall and 4 inches horizontally beyond the ledger face (or the alternate 1/4" down the ledger face), and lap the WRB over the flashing at least 2 inches. §§ R507.9.1.5–.6.
- Provide lateral resistance per § R507.9.2: install two hold‑down devices (per Figure R507.9.2(1)) with an allowable capacity of 1,500 lb each, with one within 24 inches of each end of the deck. Or, as an alternative, use four devices at 750 lb each per Figure R507.9.2(2). § R507.9.2.
(If any of these elements cannot be verified in inspection — for example, the band joist does not bear on primary structure or the required WRB/flashing cannot be installed — the deck must be made self‑supporting or engineered per § R507.8 and § R507.9.1.4.)
Related provisions
- § R507.8 — Vertical and lateral supports; general anchorage requirement for decks.
- § R507.9 — Vertical and lateral supports at band joist (includes ledger subsections).
- § R507.9.1.1 — Ledger details (material, minimum size).
- § R507.9.1.3 — Ledger‑to‑band‑joist fastener tables and predrill requirements.
- § R507.9.1.5–.7 — Flashing, WRB, and existing‑wall ledger provisions.
- § R507.9.2 — Lateral connection and hold‑down device capacities/locations.
- § R507.6.1–.2 — Joist bearing and lateral restraint requirements.
- § R507.7 — Decking attachment requirements and decking joist spacing table.
- § R507.10 — Exterior guards — attachment and load path requirements.
Code references
Grounded in the retrieved California Residential Code — click a citation to read the verbatim passage:
CRC § 9.1 High relevance — show source text
FLOORS
R507.8 Vertical and lateral supports. Where supported by attachment to an exterior wall, decks shall be positively anchored to the primary structure and designed for both vertical and lateral loads. Such attachment shall not be accomplished by the use of toenails or nails subject to withdrawal. For decks with cantilevered framing members, connection to exterior walls or other framing members shall be designed and constructed to resist uplift resulting from the full live load specified in Table R301.5 acting on the cantilevered portion of the deck. Where positive connection to the primary building structure cannot be verified during inspection, decks shall be self-supporting.
R507.9 Vertical and lateral supports at band joist. Vertical and lateral supports for decks shall comply with this section.
R507.9.1 Vertical supports. Vertical loads shall be transferred to band joists with ledgers in accordance with this section.
R507.9.1.1 Ledger details. Deck ledgers shall be a minimum 2-inch by 8-inch (51 mm by 203 mm) nominal, No. 2 grade or better pressure-preservative-treated Southern pine, incised pressure-preservative-treated hem-fir, or decay-resistant, naturally durable wood. Deck ledgers shall not support concentrated loads from beams or girders. Deck ledgers shall not be supported on stone or masonry veneer.
R507.9.1.2 Band joist details. Band joists supporting a ledger shall be a minimum 2-inch-nominal (51 mm), solid-sawn, spruce-pine-fir or better lumber or a minimum 1-inch (25 mm) nominal engineered wood rim boards in accordance with Section R502.1.7. Band joists shall bear fully on the primary structure capable of supporting all required loads.
R507.9.1.3 Ledger to band joist details. Where ledgers are fastened in accordance with Table R507.9.1.3(1), fasteners shall comply with Section R507.2.3 and shall be installed in accordance with Table R507.9.1.3(2) and Figures R507.9.1.3(1) and R507.9.1.3(2). Holes for [1] / 2 -inch (12.7 mm) lag screws shall be predrilled with two drill bits so that a hole [1] / 2 inch (12.7 mm) in diameter is drilled through the ledger and sheathing, if present, and a hole [5] / 16 inch (7.9 mm) to [3] / 8 inch (9.5 mm) in diameter is drilled through the band joist.
TABLE R507.9.1.3(1)—DECK LEDGER CONNECTION TO BAND JOIST Col2 Col3 Col4 Col5 LOADc (psf) JOIST
SPANa
(feet)ON-CENTER SPACING OF FASTENERSb (inches) ON-CENTER SPACING OF FASTENERSb (inches) ON-CENTER SPACING OF FASTENERSb (inches) LOADc (psf) JOIST
SPANa
(feet)1/2-inch diameter lag screw with
1/2-inch maximum sheathing_d,CRC § 6.4 High relevance — show source text
Exceptions:
- Where a window or door opening is located less than 2 inches (51 mm) above the ledger, flashing shall extend to the bottom of the wall opening.
- Flashing is not required where the ledger is spaced horizontally from the exterior wall covering not less than [1] / 4 inch (6.4 mm) to allow for drainage and ventilation behind the ledger.
R507.9.1.6 Water-resistive barrier. The water-resistive barrier required by Section R703.2 shall be lapped over a vertical leg of the ledger flashing or counterflashing extending up the wall by not less than 2 inches (51 mm) or the height of the vertical flashing leg, whichever is less. The water-resistive barrier shall continue from the top of the ledger flashing down the wall and behind the ledger flashing and ledger.
Exceptions:
- Flashing shall be permitted to be placed against the face of the water-resistive barrier where a self-adhering membrane counterflashing is installed not less than 2 inches (51 mm) over the vertical leg of the flashing and not less than 2 inches (51 mm) onto the water-resistive barrier.
- Flashing shall be permitted to be placed in front of the water-resistive barrier and behind the exterior wall covering where ledgers are spaced horizontally from the exterior wall not less than [1] / 4 inch (6.4 mm) to allow for drainage and ventilation behind the ledger.
R507.9.1.7 Existing walls. Where ledgers are attached to existing walls without water-resistive barriers, a water-resistive barrier shall be installed behind the ledger and ledger flashing. The water-resistive barrier shall extend to the top of the ledger flashing vertical leg and not less than [1] / 2 inch (12.7 mm) beyond the sides and bottom of the ledger. A self-adhering membrane counterflashing shall be installed not less than 2 inches (51 mm) over the vertical leg of the ledger flashing and not less than 2 inches (51 mm) onto the existing sheathing.
Exceptions:
- Where a window or door opening is located less than 2 inches (51 mm) above the ledger, flashing shall extend to the bottom of the wall opening.
- Flashing is not required where the ledger is spaced horizontally from the exterior wall covering not less than [1] / 4 inch (6.4 mm) to allow for drainage and ventilation behind the ledger.
R507.9.1.8 Exterior wall coverings. Exterior wall coverings shall be terminated above the finished deck surface in accordance with the covering manufacturer’s requirements and Chapter 7, as applicable to the type of covering.
Exception: Exterior wall coverings shall be permitted behind ledgers in accordance with Section R507.9.1.5 where capable of resisting compression forces from the ledger attachment.
CRC § 25.4 High relevance — show source text
Other maximum span provided by an accredited lumber grading or inspection agency also allowed.
c. Individual wood deck boards supported by two joists shall be considered single span and three or more joists shall be considered multiple span.|For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 degree = 0.01745 rad.
a. Maximum angle of 45 degrees from perpendicular for wood deck boards.
b. Other maximum span provided by an accredited lumber grading or inspection agency also allowed.
c. Individual wood deck boards supported by two joists shall be considered single span and three or more joists shall be considered multiple span.|For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 degree = 0.01745 rad.
a. Maximum angle of 45 degrees from perpendicular for wood deck boards.
b. Other maximum span provided by an accredited lumber grading or inspection agency also allowed.
c. Individual wood deck boards supported by two joists shall be considered single span and three or more joists shall be considered multiple span.|For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 degree = 0.01745 rad.
a. Maximum angle of 45 degrees from perpendicular for wood deck boards.
b. Other maximum span provided by an accredited lumber grading or inspection agency also allowed.
c. Individual wood deck boards supported by two joists shall be considered single span and three or more joists shall be considered multiple span.|2025 CALIFORNIA RESIDENTIAL CODE 5-39
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
FLOORS
R507.8 Vertical and lateral supports. Where supported by attachment to an exterior wall, decks shall be positively anchored to the primary structure and designed for both vertical and lateral loads. Such attachment shall not be accomplished by the use of toenails or nails subject to withdrawal. For decks with cantilevered framing members, connection to exterior walls or other framing members shall be designed and constructed to resist uplift resulting from the full live load specified in Table R301.5 acting on the cantilevered portion of the deck. Where positive connection to the primary building structure cannot be verified during inspection, decks shall be self-supporting.
R507.9 Vertical and lateral supports at band joist. Vertical and lateral supports for decks shall comply with this section.
R507.9.1 Vertical supports. Vertical loads shall be transferred to band joists with ledgers in accordance with this section.
R507.9.1.1 Ledger details. Deck ledgers shall be a minimum 2-inch by 8-inch (51 mm by 203 mm) nominal, No. 2 grade or better pressure-preservative-treated Southern pine, incised pressure-preservative-treated hem-fir, or decay-resistant, naturally durable wood. Deck ledgers shall not support concentrated loads from beams or girders. Deck ledgers shall not be supported on stone or masonry veneer.
R507.9.1.2 Band joist details. Band joists supporting a ledger shall be a minimum 2-inch-nominal (51 mm), solid-sawn, spruce-pine-fir or better lumber or a minimum 1-inch (25 mm) nominal engineered wood rim boards in accordance with Section R502.1.7. Band joists shall bear fully on the primary structure capable of supporting all required loads.
CRC § 1604.6 High relevance — show source text
1604.6 In-situ load tests. The building official is authorized to require an engineering analysis or a load test, or both, of any construction whenever there is reason to question the safety of the construction for the intended occupancy. Engineering analysis and load tests shall be conducted in accordance with Section 1708.
1604.7 Preconstruction load tests. Materials and methods of construction that are not capable of being designed by approved engineering analysis or that do not comply with the applicable referenced standards, or alternative test procedures in accordance with Section 1707, shall be load tested in accordance with Section 1709.
1604.8 Anchorage. Buildings and other structures, and portions thereof, shall be provided with anchorage in accordance with Sections 1604.8.1 through 1604.8.3, as applicable. 1604.8.1 General. Anchorage of the roof to walls and columns, and of walls and columns to foundations, shall be provided to resist the uplift and sliding forces that result from the application of the prescribed loads. 1604.8.2 Structural walls. Walls that provide vertical load-bearing resistance or lateral shear resistance for a portion of the structure shall be anchored to the roof and to all floors and members that provide lateral support for the wall or that are supported by the wall. The connections shall be capable of resisting the horizontal forces that result from the application of the prescribed loads. The required earthquake out-of-plane loads are specified in Section 1.4.4 of ASCE 7 for walls of structures assigned to Seismic Design Category A and to Section 12.11 of ASCE 7 for walls of structures assigned to all other seismic design categories. Required anchors in masonry walls of hollow units or cavity walls shall be embedded in a reinforced grouted structural element of the wall. See Sections 1609 for wind design requirements and 1613 for earthquake design requirements. 1604.8.3 Decks. Where supported by attachment to an exterior wall, decks shall be positively anchored to the primary structure and designed for both vertical and lateral loads as applicable. Such attachment shall not be accomplished by the use of toenails or nails subject to withdrawal. Where positive connection to the primary building structure cannot be verified during inspection, decks shall be self-supporting. Connections of decks with cantilevered framing members to exterior walls or other framing members shall be designed for both of the following:
- The reactions resulting from the dead load and live load specified in Table 1607.1, or the snow load specified in Section 1608, in accordance with Section 1605, acting on all portions of the deck.
- The reactions resulting from the dead load and live load specified in Table 1607.1, or the snow load specified in Section 1608, in accordance with Section 1605, acting on the cantilevered portion of the deck, and no live load or snow load on the remaining portion of the deck. 1604.9 Wind and seismic detailing. Lateral force-resisting systems shall meet seismic detailing requirements and limitations prescribed in this code and ASCE 7 Chapters 11, 12, 13, 15, 17 and 18 as applicable, even where wind load effects are greater than seismic load effects.
Exception: References within ASCE 7 to Chapter 14 shall not apply, except as specifically required herein.
1604.10 Loads on storm shelters. Loads and load combinations on storm shelters shall be determined in accordance with ICC 500.
SECTION 1605—LOAD COMBINATIONS
CRC § 9.1.7 High relevance — show source text
R507.9.1.7 Existing walls. Where ledgers are attached to existing walls without water-resistive barriers, a water-resistive barrier shall be installed behind the ledger and ledger flashing. The water-resistive barrier shall extend to the top of the ledger flashing vertical leg and not less than [1] / 2 inch (12.7 mm) beyond the sides and bottom of the ledger. A self-adhering membrane counterflashing shall be installed not less than 2 inches (51 mm) over the vertical leg of the ledger flashing and not less than 2 inches (51 mm) onto the existing sheathing.
Exceptions:
- Where a window or door opening is located less than 2 inches (51 mm) above the ledger, flashing shall extend to the bottom of the wall opening.
- Flashing is not required where the ledger is spaced horizontally from the exterior wall covering not less than [1] / 4 inch (6.4 mm) to allow for drainage and ventilation behind the ledger.
R507.9.1.8 Exterior wall coverings. Exterior wall coverings shall be terminated above the finished deck surface in accordance with the covering manufacturer’s requirements and Chapter 7, as applicable to the type of covering.
Exception: Exterior wall coverings shall be permitted behind ledgers in accordance with Section R507.9.1.5 where capable of resisting compression forces from the ledger attachment.
R507.9.2 Lateral connection. Lateral loads shall be transferred to the ground or to a structure capable of transmitting them to the ground. Where the lateral load connection is provided in accordance with Figure R507.9.2(1), hold-down tension devices shall be installed in not less than two locations per deck, within 24 inches (610 mm) of each end of the deck. Each device shall have an allowable stress design capacity of not less than 1,500 pounds (6672 N). Where the lateral load connections are provided in accordance with Figure R507.9.2(2), the hold-down tension devices shall be installed in not less than four locations per deck, and each device shall have an allowable stress design capacity of not less than 750 pounds (3336 N).
5-42 2025 CALIFORNIA RESIDENTIAL CODE
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
FLOORS
FIGURE R507.9.2(1)—DECK ATTACHMENT FOR LATERAL LOADS
WATER-PROTECTIVE BARRIER
LAPPED OVER FLASHING
"Z" FLASHING (SHOWN) OR "L" FLASHING (OPTIONAL)
HOLD-DOWN OR SIMILAR DEVICE
ATTACHED TO ADJACENT JOISTS
PER MANUFACTURER
LAG SCREWS OR BOLTS STAGGARED
APPROVED JOIST HANGER
For SI: 1 inch = 25.4 mm.
FIGURE R507.9.2(2)—DECK ATTACHMENT FOR LATERAL LOADS
WATER-RESISTING BARRIER
LAPPED OVER FLASHING
"L" FLASHING (SHOWN) OR "Z" FLASHING (OPTIONAL)
APPROVED JOIST HANGERS
LAG SCREWS OR BOLTS STAGGERED
HOLD-DOWN DEVICE MIN 750 LB. CAPACITY AT 4 LOCATIONS, EVENLY DISTRIBUTED ALONG DECK AND ONE WITHIN 24" OF EACH
END OF THE LEDGER. HOLD-DOWN DEVICES
CRC § 8.1 High relevance — show source text
- Elevated PV support structures where the usable space underneath is used for parking of emergency vehicles shall be assigned to Risk Category IV. 1604 A .6 In-situ load tests. The building official is authorized to require an engineering analysis or a load test, or both, of any construction whenever there is reason to question the safety of the construction for the intended occupancy. Engineering analysis and load tests shall be conducted in accordance with Section 1708 A .
1604 A .7 Preconstruction load tests. Materials and methods of construction that are not capable of being designed by approved engineering analysis or that do not comply with the applicable referenced standards, or alternative test procedures in accordance with Section 1707 A, shall be load tested in accordance with Section 1709 A .
1604 A .8 Anchorage. Buildings and other structures, and portions thereof, shall be provided with anchorage in accordance with Sections 1604 A .8.1 through 1604 A .8.3, as applicable. 1604 A .8.1 General. Anchorage of the roof to walls and columns, and of walls and columns to foundations, shall be provided to resist the uplift and sliding forces that result from the application of the prescribed loads. 1604 A .8.2 Structural walls. Walls that provide vertical load-bearing resistance or lateral shear resistance for a portion of the structure shall be anchored to the roof and to all floors and members that provide lateral support for the wall or that are supported by the wall. The connections shall be capable of resisting the horizontal forces that result from the application of the prescribed loads. The required earthquake out-of-plane loads are specified in Section 1.4.4 of ASCE 7 for walls of structures assigned to Seismic Design Category A and to Section 12.11 of ASCE 7 for walls of structures assigned to all other seismic design categories. For anchorage of concrete or masonry walls to roof and floor diaphragms, the out-of-plane strength design force shall not be less than 280 lb/linear ft (4.09 kN/m) of wall. Required anchors in masonry walls of hollow units or cavity walls shall be embedded in a reinforced grouted structural element of the wall. See Sections 1609 for wind design requirements and 1613 A for earthquake design requirements. 1604 A .8.3 Decks. Where supported by attachment to an exterior wall, decks shall be positively anchored to the primary structure and designed for both vertical and lateral loads as applicable. Such attachment shall not be accomplished by the use of toenails or nails subject to withdrawal. Where positive connection to the primary building structure cannot be verified during inspection, decks shall be self-supporting. Connections of decks with cantilevered framing members to exterior walls or other framing members shall be designed for both of the following:
- The reactions resulting from the dead load and live load specified in Table 1607 A .1, or the snow load specified in Section 1608, in accordance with Section 1605 A, acting on all portions of the deck.
- The reactions resulting from the dead load and live load specified in Table 1607 A .1, or the snow load specified in Section 1608 A, in accordance with Section 1605 A, acting on the cantilevered portion of the deck, and no live load or snow load on the remaining portion of the deck.
CRC § 3.3. High relevance — show source text
= On Center.
a. Steel framing shall be minimum 33-ksi steel for 33-mil and 43-mil steel, and 50-ksi steel for 54-mil steel or thicker.
b. Where cladding is attached to wood structural panel sheathing only, fastening requirements shall be in accordance with Table R703.3.3. For brick veneer tie connections to
wood structural panels, refer to Table R703.8.4(2).
c. Screws shall comply with the requirements of ASTM C1513.
d. Foam sheathing shall have a minimum compressive strength of 15 psi in accordance with ASTM C578 or ASTM C1289.|For SI: 1 inch = 25.4 mm, 1 mil = 0.0254 mm, 1 pound per square foot = 0.0479 kPa, 1 pound per square inch = 6.895 kPa.
DR = Design Required.
o.c. = On Center.
a. Steel framing shall be minimum 33-ksi steel for 33-mil and 43-mil steel, and 50-ksi steel for 54-mil steel or thicker.
b. Where cladding is attached to wood structural panel sheathing only, fastening requirements shall be in accordance with Table R703.3.3. For brick veneer tie connections to
wood structural panels, refer to Table R703.8.4(2).
c. Screws shall comply with the requirements of ASTM C1513.
d. Foam sheathing shall have a minimum compressive strength of 15 psi in accordance with ASTM C578 or ASTM C1289.|For SI: 1 inch = 25.4 mm, 1 mil = 0.0254 mm, 1 pound per square foot = 0.0479 kPa, 1 pound per square inch = 6.895 kPa.
DR = Design Required.
o.c. = On Center.
a. Steel framing shall be minimum 33-ksi steel for 33-mil and 43-mil steel, and 50-ksi steel for 54-mil steel or thicker.
b. Where cladding is attached to wood structural panel sheathing only, fastening requirements shall be in accordance with Table R703.3.3. For brick veneer tie connections to
wood structural panels, refer to Table R703.8.4(2).
c. Screws shall comply with the requirements of ASTM C1513.
d. Foam sheathing shall have a minimum compressive strength of 15 psi in accordance with ASTM C578 or ASTM C1289.|R703.16.2 Furred cladding attachment. Where steel or wood furring is used to attach cladding over foam sheathing, furring minimum fastening requirements to support the cladding weight shall be as specified in Table R703.16.2. Where placed horizontally, wood furring shall be preservative-treated wood in accordance with Section R304.1 or naturally durable wood and fasteners shall be corrosion resistant in accordance with Section R304.3. Steel furring shall have a minimum G60 galvanized coating.
|TABLE R703.16.2—FURRING MINIMUM FASTENING REQUIREMENTS FOR
APPLICATION OVER FOAM PLASTIC SHEATHING TO SUPPORT CLADDINGCRC § 5-42 High relevance — show source text
5-42 2025 CALIFORNIA RESIDENTIAL CODE
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
FLOORS
FIGURE R507.9.2(1)—DECK ATTACHMENT FOR LATERAL LOADS
WATER-PROTECTIVE BARRIER
LAPPED OVER FLASHING
"Z" FLASHING (SHOWN) OR "L" FLASHING (OPTIONAL)
HOLD-DOWN OR SIMILAR DEVICE
ATTACHED TO ADJACENT JOISTS
PER MANUFACTURER
LAG SCREWS OR BOLTS STAGGARED
APPROVED JOIST HANGER
For SI: 1 inch = 25.4 mm.
FIGURE R507.9.2(2)—DECK ATTACHMENT FOR LATERAL LOADS
WATER-RESISTING BARRIER
LAPPED OVER FLASHING
"L" FLASHING (SHOWN) OR "Z" FLASHING (OPTIONAL)
APPROVED JOIST HANGERS
LAG SCREWS OR BOLTS STAGGERED
HOLD-DOWN DEVICE MIN 750 LB. CAPACITY AT 4 LOCATIONS, EVENLY DISTRIBUTED ALONG DECK AND ONE WITHIN 24" OF EACH
END OF THE LEDGER. HOLD-DOWN DEVICES
SHALL FULLY ENGAGE DECK JOIST PER
HOLD-DOWN MANUFACTURER. ATTACHED TO
TOP PLATE STUDS OR HEADER WITH A FULLY
THREADED 3/8" DIAMETER LAG SCREW
PREDRILLED W/ MIN. 3" PENETRATION
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm.
2025 CALIFORNIA RESIDENTIAL CODE 5-43
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
FLOORS
R507.10 Exterior guards. Guards shall be constructed to meet the requirements of Sections R301.5 and R321, and this section.
R507.10.1 Support of guards. Where guards are supported on deck framing, guard loads shall be transferred to the deck framing with a continuous load path to the deck joists.
R507.10.1.1 Guards supported by side of deck framing. Where guards are connected to the interior or exterior side of a deck joist or beam, the joist or beam shall be connected to the adjacent joists to prevent rotation of the joist or beam. Connections relying only on fasteners in end grain withdrawal are not permitted.
R507.10.1.2 Guards supported on top of deck framing. Where guards are mounted on top of the decking, the guards shall be connected to the deck framing or blocking and installed in accordance with manufacturer’s instructions to transfer the guard loads to the adjacent joists.
R507.10.2 Wood posts at deck guards. Where 4-inch by 4-inch (102 mm by 102 mm) wood posts support guard loads applied to the top of the guard, such posts shall not be notched at the connection to the supporting structure.
R507.10.3 Plastic composite guards. Plastic composite guards shall comply with the provisions of Section R507.2.2.
R507.10.4 Other guards. Other guards shall be in accordance with either manufacturer’s instructions or accepted engineering principles.
5-44 2025 CALIFORNIA RESIDENTIAL CODE
CRC § 4.1 High relevance — show source text
Exception: A base course is not required where the concrete slab is installed on well-drained or sand-gravel mixture soils classified as Group I according to the United Soil Classification System in accordance with Table R401.4.1(2).
R506.3.3 Vapor retarder. A minimum 6 mil (0.006 inch; 152 μ m) polyethylene or approved vapor retarder with joints lapped not less than 6 inches (152 mm) shall be placed between the concrete floor slab and the base course or the prepared subgrade where a base course does not exist.
Exception: The vapor retarder is not required for the following:
- Garages, utility buildings and other unheated accessory structures.
- For unheated storage rooms having an area of less than 70 square feet (6.5 m [2] ) and carports.
- Driveways, walks, patios and other flatwork not likely to be enclosed and heated at a later date.
- Where approved by the building official, based on local site conditions.
R506.3.3.1 Capillary break. When a vapor retarder is required, a capillary break shall be installed in accordance with the Califor- nia Green Building Standards Code, Chapter 4, Division 4.5.
R506.3.4 Reinforcement support. Where provided in slabs-on-ground, reinforcement shall be supported to remain in place from the center to upper one-third of the slab for the duration of the concrete placement.
SECTION R507—EXTERIOR DECKS
R507.1 Decks. Wood-framed decks shall be in accordance with this section. Decks shall be designed for the live load required in Section R301.5 or the ground snow load indicated in Table R301.2, whichever is greater. For decks using materials and conditions not prescribed in this section, refer to Section R301.
R507.2 Materials. Materials used for the construction of decks shall comply with this section.
R507.2.1 Wood materials. Wood structural members shall be protected from decay where required by Sections R304.1 and R304.1.2, and protected from termites where required by Section R305.1. Where design in accordance with Section R301 is provided, wood structural members shall be designed using the wet service factor defined in AWC NDS. Sawn lumber for joists, beams and posts shall be No. 2 or better. Cuts, notches and drilled holes of preservative-treated wood members shall be treated in accordance with Section R304.1.1.
R507.2.1.1 Engineered wood products. Engineered wood products shall be in accordance with Section R502.
R507.2.2 Plastic composite deck boards, stair treads, guards or handrails. Plastic composite exterior deck boards, stair treads, guards and handrails shall comply with the requirements of ASTM D7032 and this section.
R507.2.2.1 Labeling. Plastic composite deck boards and stair treads, or their packaging, shall bear a label that indicates compliance with ASTM D7032 and includes the allowable load and maximum allowable span determined in accordance with ASTM D7032. Plastic or composite handrails and guards, or their packaging, shall bear a label that indicates compliance with ASTM D7032 and includes the maximum allowable span determined in accordance with ASTM D7032.
CRC § 9.1.3 High relevance — show source text
Lag screws or bolts shall be staggered from the top to the bottom along the horizontal run of the deck ledger in accordance with Figure R507.9.1.3(1).
b. Maximum 5 inches.
c. For engineered rim joists, the manufacturer’s recommendations shall govern.
d. The minimum distance from bottom row of lag screws or bolts to the top edge of the ledger shall be in accordance with Figure R507.9.1.3(1).|For SI: 1 inch = 25.4 mm.
a. Lag screws or bolts shall be staggered from the top to the bottom along the horizontal run of the deck ledger in accordance with Figure R507.9.1.3(1).
b. Maximum 5 inches.
c. For engineered rim joists, the manufacturer’s recommendations shall govern.
d. The minimum distance from bottom row of lag screws or bolts to the top edge of the ledger shall be in accordance with Figure R507.9.1.3(1).|For SI: 1 inch = 25.4 mm.
a. Lag screws or bolts shall be staggered from the top to the bottom along the horizontal run of the deck ledger in accordance with Figure R507.9.1.3(1).
b. Maximum 5 inches.
c. For engineered rim joists, the manufacturer’s recommendations shall govern.
d. The minimum distance from bottom row of lag screws or bolts to the top edge of the ledger shall be in accordance with Figure R507.9.1.3(1).|For SI: 1 inch = 25.4 mm.
a. Lag screws or bolts shall be staggered from the top to the bottom along the horizontal run of the deck ledger in accordance with Figure R507.9.1.3(1).
b. Maximum 5 inches.
c. For engineered rim joists, the manufacturer’s recommendations shall govern.
d. The minimum distance from bottom row of lag screws or bolts to the top edge of the ledger shall be in accordance with Figure R507.9.1.3(1).|FIGURE R507.9.1.3(2)—PLACEMENT OF LAG SCREWS AND BOLTS IN BAND JOISTS
"L" FLASHING (SHOWN) OR "Z" FLASHING (OPTIONAL)
LAG SCREWS OR BOLTS STAGGERED
APPROVED JOIST HANGER
For SI: 1 inch = 25.4 mm.
2025 CALIFORNIA RESIDENTIAL CODE 5-41
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
FLOORS
R507.9.1.4 Alternate ledger details. Alternate framing configurations supporting a ledger constructed to meet the load requirements of Section R301.5 shall be permitted.
R507.9.1.5 Ledger flashing. Where ledgers are attached to wood-frame construction, flashing shall be installed above the ledger to prevent the entry of water into the wall cavity or behind the ledger. Flashing shall extend vertically not less than 2 inches (51 mm) above the ledger. Flashing shall extend horizontally not less than 4 inches (102 mm) beyond the ledger face or shall extend to the ledger face and not less than [1] / 4 inch down the ledger face.
CRC § 3.1 High relevance — show source text
10|23/4| |F/C-6-RC-25|6″|6″ deep (4800 psi) concrete deck;1/4″ rein-
forcement bars at 71/2″ pitch with7/8″
cover;3/8″ main reinforcement bars at
31/2″ pitch perpendicular with7/8″ cover;
13′1″ span restrained.|195
psf|4 hrs|||7|1, 7|4| |F/C-6-RC-26|6″|6″ (4650 psi) concrete deck;1/4″ reinforce-
ment bars at 71/2″ pitch with7/8″ cover;3/8″
main reinforcement bars at 31/2″ pitch
perpendicular with1/2″ cover; 13′1″ span
restrained.|195
psf|2 hrs
23 min|||7|1, 2|21/4| |F/C-6-RC-27|6″|6″ deep (6050 psi) concrete deck;1/4″ rein-
forcement bars at 71/2″ pitch with7/8″
cover;3/8″ reinforcement bars at 31/2″
pitch perpendicular with1/2″ cover; 13′1″
span restrained.|195
psf|3 hrs
30 min|||7|1, 10|31/2| |F/C-6-RC-28|6″|6″ deep (5180 psi) concrete deck;1/4″ rein-
forcement bars at 8″ pitch with3/4″ cover;
1/4″ reinforcement bars at 51/2″ pitch
perpendicular with1/2″ cover; 13′1″ span
restrained.|150
psf|4 hrs|||7|1, 7|4|2025 CALIFORNIA EXISTING BUILDING CODE RESOURCE A-93
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
RESOURCE A—GUIDELINES ON FIRE RATINGS OF ARCHAIC MATERIALS AND ASSEMBLIES
TABLE 3.1—continued
FLOOR/CEILING ASSEMBLIES—REINFORCED CONCRETECol2 Col3 Col4 Col5 Col6 Col7 Col8 Col9 Col10 ITEM
CODEASSEMBLY
THICKNESSCONSTRUCTION DETAILS PERFORMANCE PERFORMANCE REFERENCE NUMBER REFERENCE NUMBER REFERENCE NUMBER NOTES REC.
HOURSITEM
CODEASSEMBLY
THICKNESSCONSTRUCTION DETAILS LOAD TIME PRE-BMS-92 BMS-92 POST-BMS-92 POST-BMS-92 POST-BMS-92 F/C-6-RC-29 6″ 6″ thick (4180 psi) concrete deck; 4″ × 3″ ×
10 lbs R.S.J.; 2′6″ C.R.S.CRC § 2.3.1 High relevance — show source text
2025 CALIFORNIA RESIDENTIAL CODE APPENDIX CK-7
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
APPENDIX CK-8 2025 CALIFORNIA RESIDENTIAL CODE
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
2025 CALIFORNIA RESIDENTIAL CODE APPENDIX NA-1
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
APPENDIX NA-2 2025 CALIFORNIA RESIDENTIAL CODE
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
Concrete Capillary break R506.2.3.1 Compressive strength R402.2 Floors (on ground) R506 Tile (roof) R905.3 Weathering Figure R301.2(1), R402.2 Construction
3D-printed Appendix BM Cavity wall masonry R608 Cob Appendix BK Extended plate walls Appendix BN Flood-resistant R306
Floors Chapter 5 Footings R403 Foundation material R402
Foundation walls R404
Foundations Chapter 4 Hemp-lime Appendix BL Masonry R606, R607, R608, R610 Pollutant control R340 Roofs Chapter 8 Steel framing R505, R603, R804 Strawbale Appendix BJ Straw-clay Appendix BI Walls Chapter 6 Waste R334.1 Wood framing R502, R602, R802 Construction Documents R106, R306.3.9
Court Emergency escape and rescue openings R319.1, R319.2.4 Means of egress R318.1 Natural light R325.1.1 Covering Exterior R703
Interior R702 Roof Chapter 9 Wall Chapter 7 Crawl Space R408
Access R408.4
Damper Fireplace R1001.7.1 Dampproofing R406 Day Care Appendix BD Defined R202 Large family day-care homes R336 Dead Loads R301.4
Decay Protection against R304 Deck
Attachment R318.5 Supported by exterior wall R507 Wood/plastic composite boards R507.2.2
Definitions Building R202 Mechanical system R202 Plumbing R202 Design Criteria R301 Alternative provisions R301.1.1 Application R301.1 Climatic and geographic R301.2 Dead load R301.4
Deflection R301.6 Engineered design R301.1.3
Accessibility R322 Accessory Dwelling Unit R202 Authority to Enforce Automatic Fire Sprinkler Systems 1.8.9.1, R313.2 Accessory Structure Elevations R306.3.2
Energy R330.5 Exterior walls R302.1
Scope R101.2 Addition (see also Existing Buildings) Carbon monoxide alarms R311.2.2 Change of occupancy R110.1 Construction R302.2.3
Frequently asked questions
What fasteners can I NOT use to attach a ledger?
Do not use toenails or nails subject to withdrawal to attach a deck ledger; the ledger attachment must be a positive connection per § R507.8 and the fastener types/spacing in § R507.9.1.3.
How high must ledger flashing extend up the wall?
Ledger flashing must extend not less than 2 inches vertically above the ledger (or the height of the flashing leg, whichever is less) and extend horizontally not less than 4 inches beyond the ledger face (or to the ledger face and 1/4 inch down the ledger face). § R507.9.1.5.
Do I always need hold‑downs for lateral loads?
Yes — lateral loads must be transferred to the ground or other structure. The code provides two prescriptive options in § R507.9.2 (two devices at 1,500 lb each near the ends, or four devices at 750 lb each distributed along the deck).
Can I attach a ledger to masonry veneer or stone?
No. Deck ledgers shall not be supported on stone or masonry veneer; the ledger must bear on approved structural framing per § R507.9.1.1 and § R507.9.1.2.
If my existing wall has no WRB, what must I do before attaching a ledger?
You must install a water‑resistive barrier behind the ledger and ledger flashing and install a self‑adhering membrane counterflashing per § R507.9.1.7.
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