Section C103 — MATERIALS OF CONSTRUCTION — 2025 California Existing Building Code (Title 24, Part 10)

[BS] C103.1 Existing materials. Existing wood materials that will be part of the retrofitting work (such as trusses, rafters, ceiling joists, top plates and wall studs) shall be in sound condition and free from defects or damage that substantially reduces the loadcarrying capacity of the member. Any wood materials found to be damaged or deteriorated shall be strengthened or replaced with new materials to provide a net dimension of sound wood equivalent to its undamaged original dimensions.

[BS] C103.2 New materials. All new materials shall comply with the standards for those materials as specified in the California Build- ing Code or the California Residential Code .

[BS] C103.3 Material specifications for retrofits. Materials for retrofitting gable end walls shall comply with Table C103.3.

[BS] TABLE C103.3—MATERIAL SPECIFICATIONS FOR RETROFITSa

COMPONENT	MINIMUM SIZE OR THICKNESS	MINIMUM MATERIAL GRADE	MINIMUM CAPACITY
Anchor blocks, compression blocks and horizontal braces	2 × 4 nominal lumber	#2 Spruce-Pine-Fir or better	NA
Nail plates	20 gage thickness 8d minimum nail holes	Galvanized sheet steel	NA
Retrofit studs	2 × 4 nominal lumber	#2 Spruce-Pine-Fir or better	NA
Gusset angle	14 gage thickness	Galvanized sheet steel	350 pounds uplift and lateral load
Stud-to-plate connector	20 gage thickness	Galvanized sheet steel	500 pounds uplift
Metal plate connectors, straps and anchors	20 gage thickness	Galvanized sheet steel	NA
For SI: 1 pound = 4.4 N. NA = Not Applicable. a. Metal plate connectors, nail plates, stud-to-plate connectors, straps and anchors shall be products approved for connecting wood-to-wood or wood-to-concrete as appropriate.

[BS] C103.4 Twists in straps. Straps shall be permitted to be twisted or bent where they transition between framing members or connection points. Straps shall be bent only once at a given location though it is permissible that they be bent or twisted at multiple locations along their length.

[BS] C103.5 Fasteners. Fasteners shall meet the requirements of Table C103.5, Sections C103.5.1 and C103.5.2, and shall be permitted to be screws or nails meeting the minimum length requirement shown in the figures and specified in the tables of this appendix. Fastener spacing shall meet the requirements of Section C103.5.3.

[BS]TABLE C103.5—NAIL AND SCREW REQUIREMENTS

FASTENER TYPE	MINIMUM SHANK DIAMETER	MINIMUM HEAD DIAMETER	MINIMUM FASTENER LENGTH
#8 screws	NA	0.28 inches	11/4 inches
8d common nails	0.131 inches	0.28 inches	21/2 inches
10d common nails	0.148 inches	0.28 inches	3 inches
For SI: 1 inch = 25.4 mm. NA = Not Applicable.

[BS] C103.5.1 Screws. Unless otherwise indicated in the appendix, screw sizes and lengths shall be in accordance with Table C103.5. Permissible screws include deck screws and wood screws. Screws shall have not less than 1 inch (25 mm) of thread. Fine threaded screws or drywall screws shall not be permitted. Select the largest possible diameter screw such that the shank adjacent to the head fits through the hole in the strap.

[BS] C103.5.2 Nails. Unless otherwise indicated in this appendix, nail sizes and lengths shall be in accordance with Table C103.5.

[BS] C103.5.3 General fastener spacing. Fastener spacing for shear connections of lumber-to-lumber shall meet the requirements shown in Figure C103.5.3 and the following conditions.

APPENDIX C-4 2025 CALIFORNIA EXISTING BUILDING CODE

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

APPENDIX C—GUIDELINES FOR THE WIND RETROFIT OF EXISTING BUILDINGS

[BS] FIGURE C103.5.3—FASTENER SPACINGS FOR LUMBER-TO-LUMBER CONNECTIONS OPERATING IN SHEAR PARALLEL TO GRAIN

FASTENER SPACING FOR LUMBER TO LUMBER

CONNECTIONS

OPERATING IN SHEAR PARALLEL TO GRAIN

END DISTANCE MINIMUM 2¹/�″

EDGE DISTANCE MINIMUM ¹/�″

DISTANCE ACROSS GRAIN MINIMUM 1″

DISTANCE PARALLEL TO GRAIN

MINIMUM 2¹/�″

For SI: 1 inch = 25.4 mm.

[BS] C103.5.3.1 General fastener spacing. Fastener spacing shall meet the following conditions except as provided for in Section C103.5.3.

The distance between fasteners and the edge of lumber that is less than 3 [1] / 2 inches (89 mm) deep in the direction of the fastener length shall be not less than [3] / 4 inch (19.1 mm).

The distance between fasteners and the edge of lumber that is more than 2 inches (51 mm) thick in the direction of the fastener length shall be not less than [1] / 2 inch (12.7 mm).
The distance between a fastener and the end of lumber shall be not less than 2 [1] / 2 inches (64 mm).
The distance between fasteners parallel to the grain (center-to-center) shall be not less than 2 [1] / 2 inches (64 mm).
The distance between fasteners perpendicular to the grain (center-to-center) in lumber that is less than 3 [1] / 2 inches (89 mm) deep in the direction of the fastener length shall be 1 inch (25 mm).
The distance between fasteners perpendicular to the grain (center-to-center) in lumber that is more than 2 inches (51 mm) thick in the direction of the fastener length shall be [1] / 2 inch (12.7 mm).

distance between fasteners perpendicular to the grain (center-to-center) in lumber that is less than 3 [1] / 2 inches (89 mm) deep in the direction of the fastener length shall be 1 inch (25 mm). 5. The distance between fasteners perpendicular to the grain (center-to-center) in lumber that is more than 2 inches (51 mm) thick in the direction of the fastener length shall be [1] / 2 inch (12.7 mm).

[BS] C103.5.3.2 Wood-to-wood connections of two members each 2 inches or less in thickness. Wood-to-wood connections fastener spacing shall meet the following conditions:

The distance between fasteners parallel to grain (center-to-center) shall be not less than 2 [1] / 2 inches (64 mm).
The distance between fasteners across grain (center-to-center) shall be not less than 1 inch (25 mm).
For wood-to-wood connections of lumber at right angles, fasteners shall be spaced not less than 2 [1] / 2 inches (64 mm) parallel to the grain and 1 inch (25 mm) perpendicular to the grain in any direction.

[BS] C103.5.3.3 Metal connectors for wood-to-wood connections. Metal connectors for wood-to-wood connections shall meet the following conditions.

Fastener spacing to edge or ends of lumber shall be as dictated by the prefabricated holes in the connectors and the connectors shall be installed in a configuration that is similar to that shown by the connector manufacturer.
Fasteners in 1 [1] / 4 -inch-wide (32 mm) metal straps that are installed on the narrow face of lumber shall be a minimum 1 / 4 inch (6.4 mm) from either edge of the lumber. Consistent with Section C103.5.3.1, fasteners shall be permitted to be spaced according to the fastener holes fabricated into the strap.
Fasteners in metal nail plates shall be spaced not less than [1] / 2 inch (12.7 mm) perpendicular to grain and not less than 1 [1] / 2 inches (38 mm) parallel to grain.