The prescriptive methods presented in this standard provide wind resistant designs and construction details for residential buildings of concrete, masonry, wood-framed and cold-formed steel-framed construction sited in high-wind regions.
The provisions of this standard are directed toward ensuring structural integrity for resisting wind loads. For design and construction requirements outside the scope of this standard, applicable requirements of the International Residential Code® or the International Building Code® shall prevail.
Provisions contained in this standard are based on an enclosed building.
Buildings outside the range of design parameters, design load criteria, and materials and methods of construction set forth in this standard are beyond the scope of this standard.
Individual elements of a building not in strict compliance with or addressed by this standard may be engineered without requiring engineering for the entire building. Elements which maintain the structural integrity of the building envelope shall comply with Chapter 6. Windows and doors that are not addressed in Chapter 6 shall be designed and installed to comply with the components and cladding loads of Section 1609 of the International Building Code.
A large number of alternatives are available to a designer for providing wind resistance. The provisions given are not intended to prevent the use of such alternate materials or methods permitted by Section 104.11 of the International Building Code.
For construction in high wind regions as established by Figure 104, inspection of framing and masonry construction shall be made after the roof, masonry, all framing, sheathing fasteners, clips, straps and bracing are in place, but prior to placement of insulation, moisture barrier, roof covering or wall covering material.
BUILDING GEOMETRY LIMITATIONS
|WALL CONSTRUCTION||MASONRY||CONCRETE||WOOD LIGHT-FRAMEa||STEEL LIGHT-FRAMEb|
|Maximum number of stories||3||2||3||3|
|Enclosure classification||Enclosed except asprovided for open insetsby Section 208||Enclosed except asprovided for open insets by Section 308||Enclosed except asprovided for openinsets by Section 308||Enclosed except asprovided for openinsets by Section 308|
|Building endwall width(parallel to roof framingdirection)3||12 ft to 40 ft 1 story 18 ft to 40 ft 2 and 3 story||40 ftmaximum||80 ftmaximum||40 ftmaximum|
|Minimum building sidewalllength (perpendicular to roof framing direction)c||0.5 timesbuilding width perpendicular||0.5 timesbuilding width perpendicular||12 ft||AISI S230Section E13.2|
|Maximum building sidewalllength (perpendicular to roof framing direction)c||2 timesbuilding width perpendicular||2 timesbuilding width perpendicular||80 ftmaximum||60 ft|
|Maximum bearing wallclear height||10 ft||10 ft||10 ft||10 ft|
|Maximum nonbearing wallclear height||22 ft||10 ft||20 ft||22 ft exteriorAISI S230 Tables E3-17a and E3-17b22 ft 10 in interior ASTM C754|
|Maximum eave heightabove grade||30 ft||not applicable||not applicable||not applicable|
|Maximum mean roof heightabove average grade||not applicable||35 ft||33 ft||33 ft|
|Roof type||gable or hip||gable or hip||gable or hip||gable or hip|
|Roof slope, 1 and 2 story||0° to 45°(0:12 - 12:12)||0° to 45°(0:12 - 12:12)||0° to 45°(0:12 - 12:12)||14° to 45°(3:12 - 12:12)|
|Roof slope, 3 story||0° to 45°(9:12 - 12:12)||not applicable||0° to 26.5°(0:12 - 6:12)||14° to 30°(3:12 - 7:12|
|Maximum roof overhang atsidewall and hip roofs allaround||4 ft||4 ft||2 ft||2 ft|
|Maximum roof overhang atendwall with outlooker framing||2 ft||2 ft||2 ft||1 ft|
|Maximum roof overhang atendwall with other framing||1 ft||2 ft||1 ft||1 ft|
The provisions of this standard apply to enclosed wood or steel framed, concrete, masonry and insulated concrete form (ICF) walled residential buildings formed by rectangular shaped elements in plan view and having the geometry shown in Table 102.
The requirements are based on all exterior walls having solid elements (walls, windows and doors) for the full perimeter of the building. Open porches not exceeding 20 feet (6096 mm) in width and constructed in accordance with Sections 208 and 308 shall be permitted.
Nonrectangular shaped buildings in plan view shall be permitted in accordance with the provisions of Section 105.
2.Foundation walls supported on cast-in-place concrete footings, and
Stemwall foundation height shall not exceed 3 feet-0 inches (914 mm) from finished grade to top of concrete or masonry.
Exception: For slab-on-grade floors, foundation wall height may exceed 3 feet-0 inches (914 mm), provided:
2.A bond beam complying with Section 205.2 is provided; and
3.The foundation wall or walls comply with Section R404 of the International Residential Code; and
4.Vertical reinforcement terminates in the bond beam in accordance with Section 205.7.2 of this standard; and
5.The top of the wall is keyed to the slab by:
a.Providing 6 × 6 W1.4 × W1.4 welded wire fabric extending 10 feet-0 inches (3048 mm) into the slab and 6 inches (152 mm) into the bond beam; or,
b.Providing No. 3 minimum reinforcing steel at 4 feet-0 inches (1219 mm) o.c. hooked into the bond beam, and extending 10 feet-0 (3048 mm) inches into the slab.
In flood hazard areas, flood-resistant construction shall be in accordance with the International Residential Code. Appendix B of this standard and FEMA 550, Recommended Residential Construction for the Gulf Coast, provide guidance for flood-resistant foundations and prescriptive designs for flood- and wind-resistant foundations for buildings with wood or light steel-framed exterior walls.
The following words and terms used in this standard shall have the meaning set forth herein:
APPROVED. Approved by the building official or other authority having jurisdiction.
AVERAGE GRADE. A reference plane representing the average of finished ground level adjoining the building at all exterior walls. When the finished ground level slopes away from the exterior walls, the reference plane shall be established by the lowest points within the area between the building and the lot line or between the building and a point 6 feet (1829 mm) from the building, whichever is closer to the building.
BALLOON-FRAME CONSTRUCTION. Construction in which the exterior wall studs extend the full height of the building from foundation plate to rafter plate.
BLOCKED DIAPHRAGM. A diaphragm in which all adjoining panel edges occur over framing or lightweight nailers (usually 2 × 4) or other primary structural supports for the specific purpose of connecting the edges of the panels. This “blocking” is provided to allow connections of panels at all edges for better shear transfer.
BOND BEAM. One or more courses of masonry units grouted solid; cast-in-place concrete; or composite precast/castin-place concrete, reinforced with longitudinal reinforcement.
BUILDING LENGTH (L). The dimension of exterior walls perpendicular to the span of roof rafters or trusses [see Figure 103(1)].
BUILDING WIDTH (W). The dimension of exterior walls parallel to the span of roof rafters or trusses [see Figure 103(1)].
CEILING HEIGHT. Nominal distance measured at the sidewall between top of floor and bottom surface of ceiling above that is directly attached to roof/floor framing system [see Figure 103(1)].
CONCRETE COVER. Protective covering of concrete over reinforcing steel.
CONTINUOUS (REINFORCING STEEL). Refers to lengths of reinforcing steel spliced together to act as a single unit, providing an uninterrupted connection capable of developing the full strength of the bar.
DESIGN WIND SPEED. Design wind speed in miles per hour (3 sec. gust) given in Figure 104 or as specified by the building official or other authority having jurisdiction.
DIAPHRAGM. A flat structural unit acting like a deep thin beam.
DRAG STRUT. A structural member that transfers axial loads between adjacent shear-resisting elements. Bond beams, top plates, joists, girders and truss chords may be used as drag struts provided connections at each end of the drag strut are capable of transferring loads (see Section 105).
ENDWALL. An exterior wall parallel to the primary floor and roof framing direction. [see Figure 103(1)].
FACE SHELL. Side wall of a hollow masonry unit.
GROUP II, III, and IV WOOD SPECIES. Classifications of wood species by specific gravity for the purpose of fastening design. Specific gravities of various species are provided in the American Forest and Paper Association’s (AF&PA) National Design Specification (NDS) for Wood Construction.
Group II Species. Species with a specific gravity of 0.49 or greater (Douglas Fir, Southern Pine, etc.).
Group III Species. Species with a specific gravity of 0.42 or greater and less than 0.49 (Hem Fir, Spruce Pine Fir, etc.).
Group IV Species. Species with a specific gravity less than 0.42 (California Redwood, Western Cedar, etc.).
GROUT. A mixture of cementitious material and aggregate to which water is added to provide desired slump.
COARSE GROUT. A mixture of portland cement, sand, pea gravel and water.
FINE GROUT. A mixture of portland cement, sand and water.
HEADER. See LINTEL.
HIGH-WIND REGION. Areas where the design wind speed equals or exceeds 100 miles per hour (44.7 m/s) or greater.
INSULATED CONCRETE FORM (ICF). A concrete forming system using stay-in-place forms of rigid foam plastic insulation, a hybrid of cement and foam insulation, a hybrid of cement and wood chips, or other insulating material for constructing cast-in-place concrete walls.
INTERIOR SHEARWALL. A shearwall located in the interior of the building; i.e., not an endwall or sidewall.
LINTEL. A beam placed over an opening in a wall.
MASONRY. A form of construction composed of concrete masonry units or clay masonry units laid up unit by unit and set in mortar.
MASONRY COVER. Protective covering for reinforcement consisting of masonry units, grout, or mortar or a combination thereof.
OVERHANG. Projection of a roof beyond the wall below.
EAVE OVERHANG. Projection of a roof beyond the sidewall.
RAKE OVERHANG. Projection of a roof beyond the gable endwall.
RUNNING BOND. The placement of masonry units such that head joints in successive courses are horizontally offset at least one quarter of the unit length.
STACK BOND. The placement of masonry units in a bond pattern such that head joints in successive courses are vertically aligned. For the purpose of this standard, requirements for stack bond shall apply to all masonry laid in other than running bond.
SHEARWALL. A wall or portion of a wall used to resist horizontal forces parallel to the wall (in-plane shear) [see Figure 205(8)].
SHEARWALL PIER. Portion of a shearwall segment adjacent to and equal in height to the opening with the shortest height on either side of the shearwall segment [see Figure 205(8)].
SHEARWALL SEGMENT. Portion of a shearwall between openings extending between horizontal diaphragms and/or floor designed to resist in-plane shear (shear parallel to the wall) [see Figure 205(8)].
SIDEWALL. An exterior wall perpendicular to the primary floor and roof framing direction [see Figure 103(1)].
STANDARD 90 DEGREE HOOK. Reinforcing steel which ends in a 90 degree bend plus extension of at least 12-bar diameters beyond the bend. Leg (hook length) = 6 inches (152 mm) for No. 3 bars, 8 inches (203 mm) for No. 4, 10 inches (254 mm) for No. 5, 12 inches (304.8 mm) for No. 6, and 14 inches (356 mm) for No. 7 bars] [see Figure 103(2)].
STANDARD 180 DEGREE HOOK. Reinforcing steel which ends in a 180-degree bend plus a minimum extension of 4-bar diameters or 21/2 inches (64 mm), whichever is greater [see Figure 103(3)].
STORY. The portion of a building included between the upper surface of a floor and upper surface of the roof or floor above.
WOOD STRUCTURAL PANEL. A structural panel manufactured in accordance with DOC PS 1 or DOC PS 2 from veneers, wood strands or wafers or a combination of veneer and wood strands or wafers bonded together with waterproof synthetic resins or other suitable bonding systems. Examples of wood structural panels are: composite panels, oriented strand board (OSB) and plywood.
WYTHE. Each continuous vertical section of a masonry wall one masonry unit in thickness.
The loads used in the design of the various structural systems and elements of the buildings are separated into:
1.The overall(or global) forces used in the design of the MAIN WIND FORCE RESISTING SYSTEMS (MWFRS), and
2.Those loads appropriate for the design of fasteners, cladding and elements of the building that must resist the much higher loadings induced over relatively small areas. The latter loads are designated COMPONENT AND CLADDING Loads (C&C).
See Appendix A.
This standard provides prescriptive requirements and other details of construction for buildings sited in wind climates of 100 to 150 miles per hour (44.7 to 67 m/s) in 10 mile per hour (4.5 m/s) increments. The appropriate minimum design wind speed to be selected for a particular geographical location shall be based on the WIND SPEED MAP given in Figure 104. In developing the provisions of the standard, a USE FACTOR of 1.0 was used throughout.
The prescriptive details provided in this standard are based on the building being located in Exposure Category B or C as defined in Sections 104.4.1 or 104.4.2. Buildings constructed using ICF and flat panel concrete walls in Section 209 shall be permitted in Exposure Category D as defined in Section 104.4.3. All other buildings located in areas that qualify as Exposure Category D shall be designed in accordance with the International Building Code.
Urban and suburban areas, wooded areas or other terrain with numerous closely spaced obstructions having the size of single-family dwellings or larger. Exposure B shall be assumed unless the site meets the definition of another type of exposure.
Open terrain with scattered obstructions, including surface undulations or other irregularities, having heights generally less than 30 feet (9144 mm) extending more than 1500 feet (457.2 m) from the building site in any quadrant. This exposure shall also apply to any building located within Exposure B-type terrain where the building is directly adjacent to open areas of Exposure C-type terrain in any quadrant for a distance of more than 600 feet (182.9 m). This category includes flat open country, grasslands and shorelines in hurricane-prone regions.
Flat, unobstructed areas exposed to wind flowing over open water (excluding shorelines in hurricane prone regions) for a distance of at least 1 mile (1.61 km). Shorelines in Exposure D include inland waterways, the Great Lakes and coastal areas of California, Oregon, Washington and Alaska. This exposure shall apply only to those buildings and other structures exposed to the wind coming from over the water. Exposure D extends inland from the shore line a distance of 1500 feet (457.2 m) or 10 times the height of the building structure, whichever is greater.
The provisions of this standard shall not apply to buildings sited where all of the following conditions exist:
1.The hill, ridge or escarpment is 60 feet (18 288 mm) or higher if located in Exposure B or 30 feet (9144 mm) or higher if located in Exposure C;
2.The maximum average slope of the hill exceeds 10 percent; and
3.The hill, ridge or escarpment is unobstructed upwind by other such topographic features for a distance from the high point of 50 times the height of the hill or 1 mile (1.61 km), whichever is greater.
Rectangular elements of nonrectangular buildings shall be considered separate buildings for purposes of determining shearwall requirements.
Walls may be offset by a maximum of 4 feet (1219 mm) (such as for projecting bays, inset porches or other irregular shapes) without requiring additional shearwalls or additional drag struts for the transference of lateral loads.
Length of the required shearwall is M, as illustrated in Figure 105(1). This length of shearwall shall be located in the “main building.”
M is the length of shearwall required for each sidewall of the main building [Figure 105(2)]. L is the length of shearwall required for each endwall of the building leg. L for the common wall shall be added to M for the same wall. This total shearwall, or shearwall segment length, may be located anywhere in the length of the main building wall if a drag strut (see Definitions) is provided across any open spaces or other nonshearwall segments in the common wall.