The provisions of this chapter are applicable to buildings that meet all of the following eligibility requirements:
ATTIC-FRAMING MEMBERS. Structural members such as ceiling joists, rafters, and roof trusses that support ceiling diaphragms or roof decking.
BALLOON FRAMING. A type of wall framing where vertical wall framing members of the gable end wall and the rectangular wall below are continuous from the top of the gable end wall to the bottom of the rectangular wall below.
COMPRESSION BLOCK. A piece of lumber used to restrain an existing or retrofit stud against movement or deflection toward the interior of the building, attached to a lateral brace and bearing directly against the primary or retrofit stud.
GABLE END WALL. The triangular wall segment at a gable end whose framing members may be conventionally framed, balloon framed, or framed with a truss.
GABLE END TRUSS. A roof truss at an exterior wall with lumber members oriented with their wide faces parallel to the plane of the wall.
GUSSET ANGLE BRACKET. Metal connectors intended by the manufacturer to connect materials at right angles to each other supplied by the manufacturer with fasteners.
LATERAL BRACE. A lumber member typically installed horizontally on the top of attic floor framing members or on the bottom of pitched roof framing members used to transfer both compression and tension loads applied by a gable wall existing, added or retrofit stud into either the ceiling or roof diaphragm.
PRIMARY STUD. An existing or added stud as defined above. A vertical member installed against the gable end wall sheathing and connected to the top and bottom chords of the gable end framing that provides the required minimum spacing of structural members supporting the wall sheathing.
RETROFIT. The process of strengthening or improving buildings or structures, or individual components of buildings or structures for the purpose of making existing conditions better serve the purpose for which they were originally intended or the purpose that current building codes intend.
RETROFIT STUD. A vertical lumber member used to supplement the strength or stiffness of an existing or added (primary) stud.
STUD-TO-PLATE CONNECTOR. A manufactured metal connector designed to connect studs to lumber plates.
Materials for retrofitting gable end walls shall comply with Table 1703.3.
MATERIAL SPECIFICATIONS FOR RETROFITS
|Component||Minimum Size |
|Minimum Material Grade or Type||Minimum Capacity|
|All lumber||2-inch nominal thickness |
minimum depth will vary accordingto application
|#2 Spruce-Pine-Fir (S) or better||Not applicable|
|Gusset angle bracket||14 gage thickness||Galvanized sheet steel approved for connecting |
wood-to-wood, wood-to-CMU, or wood-to-concrete.
|350 pounds uplift |
and lateral load
|Stud-to-plate connector||14 gage thickness||Galvanized sheet steel approved for connecting |
|500 pounds uplift|
|Metal connectors||20 gage thickness||Galvanized sheet steel approved for connecting |
wood-to-wood, wood-to-CMU, or wood-to-concrete.
|Nail plates and straps||20 gage thickness||Galvanized sheet steel approved for connecting |
Fasteners shall meet the requirements of Table 1703.5, and Sections 1703.5.1 and 1703.5.2, 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 chapter. Fasteners used to secure connectors shall be those approved by the manufacturer.
NAIL AND SCREW REQUIREMENTS
|Minimum Fastener |
|Fastener Type||Shank Diameter |
(Neglecting Galvanizing)Minimum and Maximum
Length of Thread(inches)
|Minimum Head Diameter |
|11/2||#9 screws||0.177 inches||11/4||0.28|
|8d common nails||0.131 inches||Not applicable||0.28|
|3||#9 screws||0.177 inches||11/2||0.28|
|10d common nails||0.148 inches||Not applicable||0.28|
For SI: 1 inch = 25.4 mm.
The strengthening scheme provided by this chapter requires the installation of lateral braces, retrofit studs, and other load path components to supplement existing framing. Figure 1704.1 shows the general schematic arrangement of the various elements. Lateral braces and retrofit studs shall be installed at each primary stud as specified in Sections 1706 and 1707. At each primary stud subject to strengthening, the retrofit configuration shall be determined in accordance with Table 1704.1. Retrofitting shall be in accordance with Section 1705 for installation of added studs where existing ones are too far apart; Section 1706 for the establishment of locations for retrofits and the installation of retrofit studs that strengthen primary studs; Section 1707 for the installation of lateral braces that connect ceiling and roof diaphragms via attic-framing members; Section 1708 for the two methods for the installation of straps that connect the ends of retrofit studs to lateral braces; and Section 1709 for connection of a gable end wall to the wall below.
RETROFIT CONFIGURATION AS A FUNCTION OF EXPOSURE CATEGORY, DESIGN WIND SPEED, AND STUD HEIGHT
|RETROFIT ELEMENTS||SIZE AND NUMBER OF RETROFIT ELEMENTS |
Stud length limitations based on Exposure,Basic Wind Speed, and Configuration
|Max Ultimate Design Wind |
Speed, Vult (3-sec gust)(Interpolation is not permitted)
|Connections of gable end wall to wall below. |
On center spacing (Section 1708)
|Configurations A, B, C, or D|
|Gusset angle |
|Fasteners to secure |
sill plate to wall(inches)
|D||≤ 130 mph||39||14||6'-11"||10'-11"||14'-3"||16'-0"|
|D||>130 — 140 mph||34||12||6'-7"||10'-5"||13'-7"||16'-0"|
|D||>140 — 150 mph||29||10||6'-2"||9'-9"||12'-10"||16'-0"|
|D||>150 — 160 mph||26||9||5'-11"||9'-1"||12'-0"||15'-4"|
|D||>160 — 170 mph||23||8||5'-6"||8'-7"||11'-4"||14'-9"|
|D||>170 — 180 mph||20||7||5'-2"||8'-1"||10'-8"||14'-2"|
|C||≤ 130 mph||46||16||7'-4"||11'-6"||15'-1"||16'-0"|
|C||>130 — 140 mph||39||14||7'-0"||10'-11"||14'-5"||16'-0"|
|C||>140 — 150 mph||34||12||6'-8"||10'-5"||13'-8"||16'-0"|
|C||>150 — 160 mph||30||11||6'-4"||9'-10"||13'-0"||16'-0"|
|C||>160 — 170 mph||27||9||5'-11"||9'-3"||12'-3"||15'-6"|
|C||>170 — 180 mph||24||8||5'-7"||8'-9"||11'-7"||15'-0"|
|B||≤ 130 mph||63||22||8'-2"||12'-10"||16'-0"||Note a|
|B||>130 — 140 mph||54||19||7'-9"||12'-2"||15'-0"||Note a|
|B||>140 — 150 mph||47||17||7'-5"||11'-8"||15'-3"||16'-0"|
|B||>150 — 160 mph||42||15||7'-1"||11'-2"||14'-7"||16'-0"|
|B||>160 — 170 mph||37||13||6'-10"||10'-8"||14'-0"||16'-0"|
|B||>170 — 180 mph||33||12||6'-7"||10'-4"||13'-6"||16'-0"|
|Retrofit studs Minimum size and number (Section 1706)||2 × 4||2 × 6||2 × 8||2 each 2 × 8|
|Lateral brace above and below (top and bottom) |
Minimum size and number (Section 1707)
|2 × 4||2 × 4||2 × 4||2 each 2 × 8|
|Retrofit Elements for L-bent strap applications|
|Fasteners at each end for strap connecting retrofit studs to lateral braces using 11/2-inch |
long fasteners complying with Table 1703.5 Minimum number
|3||5||6||5 at each end |
of each strap
|Fasteners to connected compression blocks to lateral braces using 3-inch long fasteners |
complying with Table 1703.5 Minimum number
|Retrofit Elements for U-bent strap applications|
|Fasteners to connect straps to each edge of lateral braces using 11/2-inch long fasteners |
complying with Table 1703.5 Minimum number
|3||4||4||4 at each end |
of each strap
For SI: 1 inch =25.4 mm, 1 foot = 304.8 mm, 1 mile per hour = 0.447 m/s.
Except as allowed by Section 1706.5, a retrofit stud shall be installed at each primary stud longer than 3 feet (914 mm) where lateral braces can be installed using the methods of Section 1707. The size of retrofit studs shall be as required by Table 1704.1 for the appropriate retrofit configuration. Where straps are installed using the L-bent strap method of Section 1708.1.1, retrofit studs shall extend from the top of the lower lateral brace up to the bottom of the upper lateral brace, except that a maximum gap of 1/8 inch (3 mm) is allowed at the bottom and 1/2 inch (13 mm) at the top. Where straps are installed using the U-bent method of Section 1708.1.2, retrofit studs shall extend beyond the ends of lateral braces such that lateral braces can fully butt against the retrofit studs.
The broad face of retrofit studs may be reduced in width by methods of cutting, boring, or notching at any number of locations along their length provided that all of the following conditions are met.
Where existing conditions prevent installation of a full length retrofit stud in accordance with Section 1706.1 or 1707.4, the retrofit stud and its associated two lateral braces shall be permitted to be wholly or partially omitted from that location by installation of a ladder assembly for Retrofit Configurations A and B as defined in Table 1704.1 provided all of the following conditions are met. This method is not allowed for Retrofit Configurations C or D.
Retrofit studs shall be permitted to be spliced provided all of the following conditions are met.
At each end of a retrofit stud, a lateral brace shall be installed as indicated in Figure 1707.1(1) or Figure 1707.1(3) for trusses and Figure 1707.1(2) or Figure 1707.1(4) for conventionally framed gable end walls. Lateral braces shall be allowed to be omitted in accordance with Section 1706.6 or 1707.4.1. Alternative methods for providing lateral bracing are allowable in accordance with Section 1707.4. Lateral braces shall be minimum 2 × 4 lumber except as required by Section 1706.6 or 1707.4.1.
Lateral braces shall be placed approximately perpendicular to the attic-framing members and extend so they are attached to a minimum of three attic-framing members. The attic-framing member farthest from the gable end wall shall be a minimum of 6 feet (1829 mm) from the exterior sheathing or siding on the gable end wall. Lateral braces shall be installed with their wide faces across attic-framing members. Where the method of Section 1708.1.1 is used, lateral braces shall butt against the sheathing or siding of the wall. Where the method of Section 1708.1.2 is used, lateral braces shall butt against the retrofit studs.
Where ceiling joists or truss bottom chords are deeper than 6 inches (152 mm), an anchor block shall be installed in each space between ceiling members along the length of the lateral brace except for the space next to the gable end wall.
Anchor blocks shall be fastened to lateral braces with a single row of 8d common nail, 10d common nails or #9 screws with minimum penetration into lateral braces equal to the thickness of the anchor block or 1 inch (25.4 mm) whichever is greater. The minimum number of fastener shall be the maximum that can be placed in a single row with minimum 23/4-inches (70 mm) distance between fasteners and 23/4-inches (70 mm) distance to ends of anchor blocks except that the number of fasteners need not exceed three per anchor block made of nominal 2-inch thick lumber. For nominal 2-inch thick lumber anchor blocks, the number of fasteners need not exceed three fasteners per anchor block.
Where existing conditions prevent installation of lateral braces in accordance with Section 1707.2, lateral braces shall be permitted to be omitted for Retrofit Configurations A and B, as defined in Table 1704.1, provided all of the following conditions are met. This method is not allowed for Retrofit Configurations C or D.
Where existing conditions prevent the installation of lateral braces of required length in accordance with Section 1707.1, a splice member shall be permitted to be installed to bridge interruptions. Splice members shall be at minimum the same size lumber as the lateral braces they bridge. Although Figure 1707.4.2 illustrates the general methods that can be used where attic-framing members are spaced 24-inches (610 mm) o.c., the methods apply to other on center spacings. Splice members may extend beyond those shown and are allowed to be fastened to the main lateral brace segments farther than shown. Splice members shall be fastened at each end using the number of fasteners equal to the total number that would be required to be placed in total in that part of lateral braces more distant from the gable end wall. For a lateral brace that requires three fasteners at each roof framing members and installation across three roof framing members, the number of fasteners in the splice need not be more than nine fasteners if the interruption is between the gable end wall and the first attic-framing member; six fasteners if between the first and second framing members, and three fasteners if between subsequent interruptions. Fasteners shall be spaced 1/2 inch (13 mm) from the edges of lateral braces, 1 inch from each other, 1/2 inch (13 mm) from the edge of attic members, and minimum 23/4 inches (25.4 mm) from the ends of lateral braces and from the ends of splice members.
Where conditions exist that prevent installation of lateral braces in accordance with Section 1707.4.1 or 1707.4.2, lateral braces shall be permitted to be shortened, except where the brace is adjacent to an omitted lateral brace of Section 1707.4.1, provided all of the following conditions are met.
Where existing conditions prevent installation of lateral braces on top or bottom chords of trusses, they shall be permitted to be installed on diagonal webs or vertical members of trusses provided all of the following conditions are met.
For Configurations A, B and C, retrofit studs shall be attached to lateral braces in accordance with Figure 1708.1.1(1) and Figure 1707.1(1) or 1707.1(2). For Configuration D, retrofit studs shall be attached to lateral braces in accordance with Figure 1708.1.1(2) and Figure 1707.1(1) or Figure 1707.1(2). Attachments shall comply with the following conditions except where attachments of retrofit studs at omitted lateral braces are in conformance with Section 1707.4.1.
For Configurations A, B and C, retrofit studs shall be attached to lateral braces in accordance with Figures 1708.1.2(1) and Figure 1707.1(3) or 1707.1(4). For Configuration D, retrofit studs shall be attached to lateral braces in accordance with Figures 1708.1.2(2) and Figure 1707.1(3) or 1707.1(4). Attachments shall comply with the following conditions except where attachments of retrofit studs at omitted lateral braces are in conformance with Section 1707.4.1.
Truss gable end walls shall be attached to the wall below using gusset angle brackets fastened to the bottom chord of roof trusses and to the wall below and spaced in accordance with Table 1704.1. Fasteners shall be placed a minimum of 5/8 inch (15.875 mm) from edges of lumber. Fasteners shall be permitted to penetrate truss plates. Four fasteners shall be effectively installed through each leg of gusset angles.
Exception: Where existing conditions prevent effective installation of all four fasteners into each leg of a gusset angle bracket, a supplementary gusset angle bracket shall be installed a minimum of 23/4 inches (70 mm) from and a maximum of 8 inches (203 mm) from the one without the four fasteners in each leg. The number of effectively installed fasteners securing the corresponding leg of the supplementary gusset angle bracket shall at least equal the number not effectively installed on the first gusset angle bracket.
The gable end walls shall be connected to the wall below using one of the following methods.