This chapter applies to the determination of wind pressures on components and cladding (C&C) on buildings. Part 1 is applicable to an enclosed or partially enclosed Low-rise building (see definition in Section 26.2) or Building with h ≤ 60 ft ( m). The building has a flat roof, gable roof, multispan gable roof, hip roof, monoslope roof, stepped roof, or sawtooth roof, and the wind pressures are calculated from a wind pressure equation. Part 2 is a simplified approach and is applicable to an enclosed Low-rise building (see definition in Section 26.2) or Building with h ≤ 60 ft ( m). The building has a flat roof, gable roof, or hip roof, and the wind pressures are determined directly from a table. Part 3 is applicable to an enclosed or partially enclosed building with h 60 ft ( m). The building has a flat roof, pitched roof, gable roof, hip roof, mansard roof, arched roof, or domed roof, and the wind pressures are calculated from a wind pressure equation.

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Part 4 is a simplified approach and is applicable to an enclosed building with h ≤ 160 ft (48.8 m). The building has a flat roof, gable roof, hip roof, monoslope roof, or mansard roof, and the wind pressures are determined directly from a table.

Part 5 is applicable to an open building of all heights having a pitched free roof, monoslope free roof, or trough free roof. Part 6 is applicable to building appurtenances such as roof overhangs and parapets and rooftop equipment. Based on the exposure category determined in Section 26.7.3, a velocity pressure exposure coefficient K z or K h, as applicable, shall be determined from Table 30.3-1. For a site located in a transition zone between exposure categories, that is, near to a change in ground surface roughness, intermediate values of K z or K h, between those shown in Table 30.3-1 are permitted, provided that they are determined by a rational analysis method defined in the recognized literature.

Velocity Pressure Exposure Coefficients, K h and K z Table 30.3-1 Notes:. The velocity pressure exposure coefficient Kz may be determined from the following formula: For 15 ft. ≤ z ≤ z g For z. The provisions of Section 30.4 are applicable to an enclosed and partially enclosed.

Low-rise building (see definition in Section 26.2) or. Building with h ≤ 60 ft (18.3 m). The building has a flat roof, gable roof, multispan gable roof, hip roof, monoslope roof, stepped roof, or sawtooth roof. The steps required for the determination of wind loads on components and cladding for these building types are shown in Table 30.4-1. Table 30.4-1 Steps to Determine C&C Wind Loads for Enclosed and Partially Enclosed Low-Rise Buildings Step 1: Determine risk category, see Table 1.5-1 Step 2: Determine the basic wind speed, V, for applicable risk category, see Fig.

26.5-1A, B, or C Step 3: Determine wind load parameters. Walls, see Fig. 30.4-1. Flat roofs, gable roofs, hip roofs, see Fig. 30.4-2. Stepped roofs, see Fig.

30.4-3. Multispan gable roofs, see Fig. 30.4-4. Monoslope roofs, see Fig. 30.4-5. Sawtooth roofs, see Fig.

30.4-6. Domed roofs, see Fig.

30.4-7. Arched roofs, see Fig. 27.4-3 note 4 Step 7: Calculate wind pressure, p, Eq. 30.4-1 Components and Cladding h ≤ 60 ft. Figure 30.4-1 External Pressure Coefficients, GC p Walls Enclosed, Partially Enclosed Buildings Notes:. Vertical scale denotes GC p to be used with q h. Horizontal scale denotes effective wind area, in square feet (square meters).

Plus and minus signs signify pressures acting toward and away from the surfaces, respectively. Each component shall be designed for maximum positive and negative pressures. Values of GC p for walls shall be reduced by 10% when θ ≤ 10°. Notation: a: 10 percent of least horizontal dimension or 0.4h, whichever is smaller, but not less than either 4% of least horizontal dimension or 3 ft (0.9 m). H: Mean roof height, in feet (meters), except that eave height shall be used for θ ≤ 10°.

Θ: Angle of plane of roof from horizontal, in degrees. Components and Cladding h ≤ 60 ft. Figure 30.4-2A External Pressure Coefficients, GC p Gable Roofs θ ≤ 7° Enclosed, Partially Enclosed Buildings Notes:. Vertical scale denotes GC p to be used with q h. Horizontal scale denotes effective wind area, in square feet (square meters).

Plus and minus signs signify pressures acting toward and away from the surfaces, respectively. Each component shall be designed for maximum positive and negative pressures. If a parapet equal to or higher than 3 ft (0.9m) is provided around the perimeter of the roof with θ ≤ 7°, the negative values of GC p in Zone 3 shall be equal to those for Zone 2 and positive values of GC p in Zones 2 and 3 shall be set equal to those for wall Zones 4 and 5 respectively in Figure 30.4-1. Values of GC p for roof overhangs include pressure contributions from both upper and lower surfaces. Notation: a: 10 percent of least horizontal dimension or 0.4h, whichever is smaller, but not less than either 4% of least horizontal dimension or 3 ft (0.9 m). H: Eave height shall be used for θ ≤ 10°.

Θ: Angle of plane of roof from horizontal, in degrees. Components and Cladding h ≤ 60 ft. Figure 30.4-2B External Pressure Coefficients, GC p Gable/Hip Roofs 7°. P = q h( GC p) - ( GC pi) (lb/ft 2) (N/m 2) (30.4-1) where q h = velocity pressure evaluated at mean roof height h as defined in (GC p) = external pressure coefficients given in: - Figure 30.4-1 (walls) - Figures. 30.4-2A to 30.4-2C (flat roofs, gable roofs,and hip roofs) - Figure 30.4-3 (stepped roofs) - Figure 30.4-4 (multispan gable roofs) - Figures 30.4-5A and 30.4-5B (monoslope roofs) - Figure 30.4-6 (sawtooth roofs) - Figure 30.4-7 (domed roofs) - Figure 27.4-3, note 4 (arched roofs) (GC pi) = internal pressure coefficient given in Table 26.11-1 User Note: Use Part 1 of to determine wind pressures on C&C of enclosed and partially enclosed low-rise buildings having roof shapes as specified in the applicable figures. The provisions in Part 1 are based on the envelope procedure with wind pressures calculated using the specified equation as applicable to each building surface.

For buildings for which these provisions are applicable, this method generally yields the lowest wind pressures of all analytical methods contained in this standard. The provisions of Section 30.5 are applicable to an enclosed. Low-rise building (see definition in Section 26.2) or. Building with h ≤ 60 ft (18.3 m). The building has a flat roof, gable roof, or hip roof. The steps required for the determination of wind loads on components and cladding for these building types are shown in Table 30.5-1. Table 30.5-1 Steps to Determine C&C Wind Loads for Enclosed Low-Rise Buildings (Simplified Method) Step 1: Determine risk category, see Table 1.5-1 Step 2: Determine the basic wind speed, V, for applicable risk category see Figure 26.5-1A, B, or C Step 3: Determine wind load parameters:.

Exposure category B, C, or D, see Section 26.7. Topographic factor, K zt, see Section 26.8 and Figure 26.8-1 Step 4: Enter figure to determine wind pressures at h = 30 ft., p net30, see Fig. 30.5-1 Step 5: Enter figure to determine adjustment for building height and exposure, λ, see Fig. 30.5-1 Step 6: Determine adjusted wind pressures, p net, see Eq. Components and Cladding - Method 1 h ≤ 60 ft. Figure 30.5-1 Design Wind Pressures Walls & Roofs Enclosed Buildings Notes:.

Pressures shown are applied normal to the surface, for exposure B, at h=30 ft (9.1 m). Adjust to other conditions using Equation 30.5-1. Plus and minus signs signify pressures acting toward and away from the surfaces, respectively. For hip roofs with θ ≤ 25°, Zone 3 shall be treated as Zone 2. For effective wind areas between those given, value may be interpolated, otherwise use the value associated with the lower effective wind area.

Notation: a: 10 percent of least horizontal dimension or 0.4h, whichever is smaller, but not less than either 4% of least horizontal dimension or 3 ft (0.9 m). H: Mean roof height, in feet (meters), except that eave height shall be used for roof angles. For the design of components and cladding the building shall comply with all the following conditions:. The mean roof height h must be less than or equal to 60 ft ( m) h ≤ 60 ft ( m).

The building is enclosed as defined in and conforms to the wind-borne debris provisions of Section. The building is a regular-shaped building or structure as defined in. The building does not have response characteristics making it subject to across-wind loading, vortex shedding, or instability due to galloping or flutter; and it does not have a site location for which channeling effects or buffeting in the wake of upwind obstructions warrant special consideration.

The building has either a flat roof, a gable roof with θ ≤ 45°, or a hip roof with θ ≤ 27°. P net = λ K ztp net30 (30.5-1) where λ = adjustment factor for building height and exposure from Fig. 30.5-1 K zt = topographic factor as defined in evaluated at 0.33 mean roof height, 0.33h p net30 = net design wind pressure for Exposure B, at h = 30 ft (9.1 m), from Fig. 30.5-1 User Note: Part 2 of is a simplified method to determine wind pressures on C&C of enclosed low-rise buildings having flat, gable, or hip roof shapes. The provisions of Part 2 are based on the envelope procedure of Part 1 with wind pressures determined from a table and adjusted as appropriate. The provisions of Section 30.6 are applicable to an enclosed or partially enclosed building with a mean roof height h 60 ft.

(18.3 m) with a flat roof, pitched roof, gable roof, hip roof, mansard roof, arched roof, or domed roof. The steps required for the determination of wind loads on components and cladding for these building types are shown in Table 30.6-1. Table 30.6-1 Steps to Determine C&C Wind Loads for Enclosed or Partially Enclosed Building with h 60 ft Step 1: Determine risk category, see Table 1.5-1 Step 2: Determine the basic wind speed, V, for applicable risk category, see Figure 26.5-1A, B, or C Step 3: Determine wind load parameters:. Wind directionality factor, K d, see Section 26.6 and Table 26.6-1. Exposure category B, C, or D, see Section 26.7. Topographic factor, K zt, see Section 26.8 and Fig.

26.8-1. Enclosure classification, see Section 26.10. Internal pressure coefficient, (GC pi), see Section 26.11 and Table 26.11-1 Step 4: Determine velocity pressure exposure coefficient, K z or K h, see Table 30.3-1 Step 5: Determine velocity pressure, q h, Eq. 30.3-1 Step 6: Determine external pressure coefficient, (GC p). Walls and flat roofs (θ 60 ft Figure 30.6-1 External Pressure Coefficients, GC p Walls & Roofs Enclosed, Partially Enclosed Buildings Notes:. Vertical scale denotes GC p to be used with appropriate q z or q h.

Horizontal scale denotes effective wind area A, in square feet (square meters). Plus and minus signs signify pressures acting toward and away from the surfaces, respectively. Use qz with positive values of GC p and q h with negative values of GC p. Each component shall be designed for maximum positive and negative pressures.

Coefficients are for roofs with angle θ ≤ 10°. For other roof angles and geometry, use GC p values from Fig. 30.4-2A, B and C and attendant q h based on exposure defined in Section 26.7. If a parapet equal to or higher than 3 ft (0.9m) is provided around the perimeter of the roof with θ ≤ 10°, Zone 3 shall be treated as Zone 2. Notation: a: 10 percent of least horizontal dimension, but not less than 3 ft (0.9 m). H: Mean roof height, in feet (meters), except that eave height shall be used for θ ≤ 10°.

Z: height above ground, in feet (meters). Θ: Angle of plane of roof from horizontal, in degrees. P = q(GC p) - q i(GC pi) (lb/ft 2) (N/m 2) (30.6-1) where q = q z for windward walls calculated at height z above the ground q = q h for leeward walls, side walls, and roofs evaluated at height h q i = q h for windward walls, side walls, leeward walls, and roofs of enclosed buildings and for negative internal pressure evaluation in partially enclosed buildings q i = q z for positive internal pressure evaluation in partially enclosed buildings where height z is defined as the level of the highest opening in the building that could affect the positive internal pressure. For positive internal pressure evaluation, q i may conservatively be evaluated at height h (q i = q h) (GC p) = external pressure coefficients given in: - Fig. 30.6-1 for walls and flat roofs - Fig. 27.4-3, footnote 4, for arched roofs - Fig. 30.4-7 for domed roofs - Note 6 of Fig.

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30.6-1 for other roof angles and geometries (GC pi) = internal pressure coefficient given in Table 26.11-1 q and q i shall be evaluated using exposure defined in. EXCEPTION: In buildings with a mean roof height h greater than 60 ft ( m) and less than 90 ft ( m), (GC p) values from Figs. 30.4-1 through 30.4-6 shall be permitted to be used if the height to width ratio is one or less. User Note: Use Part 3 of for determining wind pressures for C&C of enclosed and partially enclosed buildings with h 60 ft. Having roof shapes as specified in the applicable figures. These provisions are based on the directional procedure with wind pressures calculated from the specified equation applicable to each building surface. The provisions of Section 30.7 are applicable to an enclosed building having a mean roof height h ≤ 160 ft.

(48.8 m) with a flat roof, gable roof, hip roof, monoslope roof, or mansard roof. The steps required for the determination of wind loads on components and cladding for these building types are shown in Table 30.7-1. Table 30.7-1 Steps to Determine C&C Wind Loads for Enclosed Building with h ≤ 160 ft Step 1: Determine risk category of building, see Table 1.5-1 Step 2: Determine the basic wind speed, V, for applicable risk category,see Figure 26.5-1A, B, or C Step 3: Determine wind load parameters:. Exposure category B, C, or D, see Section 26.7 Step 4: Enter Table 30.7-2 to determine pressure on walls and roof, p, using Eq. Roof types are. Flat roof (θ.

H = mean roof height (ft) V = Basic wind speed (mph) Components and Cladding - Part 4 h ≤ 160 ft Table 30.7-2 C & C Effective Wind Area C&C Wall and Roof Pressures Enclosed Buildings Reduction Factors Effective Wind Area Roof Form Sign Pressure Zone 1 Zone 2 Zone 3 Zone 4 Zone 5 Flat Flat Minus Plus D NA D NA D NA C D E D Gable, Mansard Gable, Mansard Minus Plus B B C B C B C D E D Hip HIp Minus Plus B B C B C B C D E D Monoslope Monoslope Plus Minus A C B C D C C D E D Overhangs All A A B NA NA Table 30.7-2 Components and Cladding - Part 4 Exposure C C&C V = 110-120 mph h = 15-80 ft. Table 30.7-2 Components and Cladding - Part 4 Exposure C C&C V = 130-150 mph h = 15-80 ft. Table 30.7-2 Components and Cladding - Part 4 Exposure C C&C V = 160-200 mph h = 15-80 ft. Table 30.7-2 Components and Cladding - Part 4 Exposure C C&C V = 110-120 mph h = 90-160 ft. Table 30.7-2 Components and Cladding - Part 4 Exposure C C&C V = 130-150 mph h = 90-160 ft.

Table 30.7-2 Components and Cladding - Part 4 Exposure C C&C V = 160-200 mph h = 90-160 ft. Design wind pressures on the designated zones of walls and roofs surfaces shall be determined from Table 30.7-2 based on the applicable basic wind speed V, mean roof height h, and roof slope 8. Tabulated pressures shall be multiplied by the exposure adjustment factor (EAF) shown in the table if exposure is different than Exposure C.

Pressures in Table 30.7-2 are based on an effective wind area of 10 ft 2 (0.93 m 2). Reductions in wind pressure for larger effective wind areas may be taken based on the reduction multipliers (RF) shown in the table. Pressures are to be applied over the entire zone shown in the figures. Final design wind pressure shall be determined from the following equation. Design wind pressures on parapet surfaces shall be based on wind pressures for the applicable edge and comer zones in which the parapet is located, as shown in Table 30.7-2, modified based on the following two load cases:.

Load Case A shall consist of applying the applicable positive wall pressure from the table to the front surface of the parapet while applying the applicable negative edge or comer zone roof pressure from the table to the back surface. Load Case B shall consist of applying the applicable positive wall pressure from the table to the back of the parapet surface and applying the applicable negative wall pressure from the table to the front surface. Pressures in Table 30.7-2 are based on an effective wind area of 10 sf. Reduction in wind pressure for larger effective wind area may be taken based on the reduction factor shown in the table. User Note: Part 4 of Chapter 30 is a simplified method for determining wind pressures for C&C of enclosed and partially enclosed buildings with h ≤ 160 ft. Having roof shapes as specified in the applicable figures. These provisions are based on the directional procedure from Part 3 with wind pressures selected directly from a table and adjusted as applicable.

Pressures are to be applied to the parapet in accordance with Fig. The height h to be used with Fig. 30.7-1 to determine the pressures shall be the height to the top of the parapet. Determine final pressure from Equation 30.7-1.

Components and Cladding - Part 4 h ≤ 160 ft Figure 30.7-1 Parapet Wind Loads Application of Parapet Wind Loads Enclosed Simple Diaphragm Building Windward Parapet Load Case A. Windward parapet pressure (p 1) is determined using the positive wall pressure (p 5) zones 4 or 5 from Table 30.7-2.

Leeward parapet pressure (p 2) is determined using the negative roof pressure (p 7) zones 2 or 3 from Table 30.7-2. Leeward Parapet Load Case B. Windward parapet pressure (p 3) is determined using the positive wall pressure (p 5) zones 4 or 5 from Table 30.7-2. Leeward parapet pressure (p 4) is determined using the negative wall pressure (p 6) zones 4 or 5 from Table 30.7-2. Design wind pressures on roof overhangs shall be based on wind pressures shown for the applicable zones in Table 30.7-2 modified as described herein.

For Zones 1 and 2, a multiplier of 1.0 shall be used on pressures shown in Table 30.7-2. For Zone 3, a multiplier of 1.15 shall be used on pressures shown in Table 30.7-2. Pressures in Table 30.7-2 are based on an effective wind area of 10 sf. Reductions in wind pressure for larger effective wind areas may be taken based on the reduction multiplier shown in Table 30.7-2.

Pressures on roof overhangs include the pressure from the top and bottom surface of overhang. Pressures on the underside of the overhangs are equal to the adjacent wall pressures. Refer to the overhang drawing shown in Fig.

Determine final pressure from Equation 30.7-1. Components and Cladding - Part 4 h ≤ 160 ft Figure 30.7-2 Roof Overhang Wind Loads Application of Overhang Wind Loads Enclosed Simple Diaphragm Building P ovh = 1.0 x roof pressure p from tables for edge Zones 1, 2 P ovh = 1.15 x roof pressure p from tables for comer Zone 3 Notes:.

P ovh = roof pressure at overhang for edge or corner zone as applicable from figures in roof pressure table. P ovh from figures includes load from both top and bottom surface of overhang. Pressure p s at soffit of overhang can be assumed same as wall pressure p w. The provisions of Section 30.8 are applicable to an open building of all heights having a pitched free roof, monosloped free roof, or troughed free roof. The steps required for the determination of wind loads on components and cladding for these building types is shown in Table 30.8-1. P = q hGC N (30.8-1) where q h = velocity pressure evaluated at mean roof height h using the exposure as defined in Section 26. 7.3 that results in the highest wind loads for any wind direction at the site G = gust-effect factor from C N = net pressure coefficient given in: - Fig.

30.8-1 for monosloped roof - Fig. 30.8-2 for pitched roof - Fig. 30.8-3 for troughed roof Net pressure coefficients C N include contributions from top and bottom surfaces. All load cases shown for each roof angle shall be investigated. Plus and minus signs signify pressure acting toward and away from the top surface of the roof, respectively. P = q p( GC p) - ( GC pi) (30.9-1) where q p = velocity pressure evaluated at the top of the parapet (GC p) = external pressure coefficient given in - Fig.

30.4-1 for walls with h ≤ 60 ft ( 48.8 m) - Figs. 30.4-2A to 30.4-2C for flat roofs, gable roofs,and hip roofs - Fig.

30.4-3 for stepped roofs- Fig. 30.4-4 for multispan gable roofs - Figs. 30.4-5A and 30-5B for monoslope roofs - Fig. 30.4-6 for sawtooth roofs - Fig.

30.4-7 for domed roofs of all heights - Fig. 30.6-1 for walls and flat roofs with h 60 ft(18.3 m)- Fig. 27.4-3 note 4 for arched roofs (GC pi) = internal pressure coefficient from Table 26.11-1, basedon the porosity of the parapet envelope Two load cases, see Fig. 30.9-1, shall be considered:. Load Case A: Windward parapet shall consist of applying the applicable positive wall pressure from Fig. 30.4-1 h ≤ 60 ft (18.3 m) or Fig. 30.6-1 h 60 ft (18.3 m) to the windward surface of the parapet while applying the applicable negative edge or corner zone roof pressure from Figs.

30.4-2 (A, B, or C), 30.4-3, 30.4-4, 30.4-5 (A or B), 30.4-6, 30.4-7, Fig. 27.4-3 note 4, or Fig.

30.6-1 h 60 ft (18.3 m) as applicable to the leeward surface of the parapet. Load Case B: Leeward parapet shall consist of applying the applicable positive wall pressure from Fig. 30.4-1 h ≤ 60 ft (18.3 m) or Fig. 30.6-1 h 60 ft (18.3 m) to the windward surface of the parapet, and applying the applicable negative wall pressure from Fig. 30.4-1 h ≤ 60 ft (18.3 m) or Fig. 30.6-1 h 60 ft (18.3 m) as applicable to the leeward surface. Edge and corner zones shall be arranged as shown in the applicable figures.

(GC p) shall be determined for appropriate roof angle and effective wind area from the applicable figures. If internal pressure is present, both load cases should be evaluated under positive and negative internal pressure. The steps required for the determination of wind loads on component and cladding of parapets are shown in Table 30.9-1. User Note: Use Part 6 of Chapter 30 for determining wind pressures for C&C on roof overhangs and parapets of buildings. These provisions are based on the directional procedure with wind pressures calculated from the specified equation applicable to each roof overhang or parapet surface. Table 30.9-1 Steps to Determine C&C Wind Loads for Parapets Step 1: Determine risk category of building, see Table 1.5-1 Step 2: Determine the basic wind speed, V, for applicable risk category,see Figure 26.5-1A, B, or C Step 3: Determine wind load parameters:. Wind directionality factor, K d, see Section 26.6 and Table 26.6-1.

Exposure category B, C, or D, see Section 26.7. Topographic factor, K zt, see Section 26.8 and Fig. 26.8-1. Enclosure classification, see Section 26.10.

Internal pressure coefficient, (GC pi), see Section 26.11 and Table 26.11-1 Step 4: Determine velocity pressure exposure coefficient, K h, at top of the parapet, see Table 30.3-1 Step 5: Determine velocity pressure, q p, at the top of the parapet using Eq. 30.3-1 Step 6: Determine external pressure coefficient for wall and roof surfaces adjacent to parapet, (GC p). Walls with h ≤ 60 ft., see Fig. 30.4-1. Flat, gable, and hip roofs, see Figs. 30.4-2A to 30.4-2C.

Stepped roofs, see Fig. 30.4-3. Multispan gable roofs, see Fig. 30.4-4. Monoslope roofs, see Figs.

30.4-5A and 30.4-5B. Sawtooth roofs, see Fig. 30.4-6.

Domed roofs of all heights, see Fig. 30.4-7. Walls and flat roofs with h 60 ft., see Fig. 30.6-1. Arched roofs, see note 4 of Fig. 27.4-3 Step 7: Calculate wind pressure, p, using Eq. 30.9-1 on windward andleeward face of parapet, considering two load cases (Case A and Case B) as shown in Fig.

Components and Cladding - Part 6 All Building Heights Figure 30.9-1 Parapet Wind Loads C & C Parapet Wind Loads All Building Types Windward Parapet Load Case A. Windward parapet pressure (p 1) is determined using the positive wall pressure (p 5) zones 4 or 5 from the applicable figure. Leeward parapet pressure (p 2) is detennined using the negative roof pressure (p 7) zones 2 or 3 from the applicable figure. Leeward Parapet Load Case B. Windward parapet pressure (p 3) is determined using the positive wall pressure (p 5) zones 4 or 5 from the applicable figure. Leeward parapet pressure (p 4) is determined using the negative wall pressure (p 6) zones 4 or 5 from the applicable figure.

P = q h( GC p) - ( GC pi) (lb/ft 2) (N/m 2) (30.10-1) where q h = velocity pressure from Section 30.3.2 evaluated at mean roof height h using exposure defined in Section 26.7.3 (GC p) = external pressure coefficients for overhangs given in Figs. 30.4-2A to 30.4-2C (flat roofs, gable roofs, and hip roofs), including contributions from top and bottom surfaces of overhang. The external pressure coefficient for the covering on the underside of the roof overhang is the same as the external pressure coefficient on the adjacent wall surface, adjusted for effective wind area,determined from Figure 30.4-1 or Figure 30.6-1 as applicable (GC pi) = internal pressure coefficient given in Table 26.11-1 The steps required for the determination of wind loads on components and cladding of roof overhangs are shown in Table 30.10-1. Table 30.10-1 Steps to Determine C&C Wind Loads for Roof Overhangs Step 1: Determine risk category of building, see Table 1.5-1 Step 2: Determine the basic wind speed, V, for applicable risk category, see Figure 26.5-1A, B, or C Step 3: Determine wind load parameters:. Wind directionality factor, K d, see Section 26.6 and Table 26.6-1. Exposure category B, C, or D, see Section 26.7. Topographic factor, K zt, see Section 26.8 and Fig.

26.8-1. Enclosure classification, see Section 26.10. Internal pressure coefficient, (GC pi), see Section 26.11 and Table 26.11-1 Step 4: Determine velocity pressure exposure coefficient, K h, see Table 30.3-1 Step 5: Determine velocity pressure, q h, at mean roof height h using Eq. 30.3-1 Step 6: Determine external pressure coefficient, (GC p), using Figs. 30.4-2A through C for flat, gabled, and hip roofs.

Step 7: Calculate wind pressure, p, using Eq. Refer to Figure 30.10-1 Components and Cladding All Building Heights Figure 30.10-1 Wind Loading - Roof Overhangs C & C Wind Load on Roof Overhangs All Building Types Notes:. Net roof pressure p ovh on roof overhangs is determined from interior, edge or comer zones as applicable from figures. Net pressure p ovh from figures includes pressure contribution from top and bottom surfaces of roof overhang. Positive pressure at roof overhang soffit p s is the same as adjacent wall pressure p w.

The components and cladding pressure on each wall of the rooftop structure shall be equal to the lateral force determined in accordance with divided by the respective wall surface area of the rooftop structure and shall be considered to act inward and outward. The components and cladding pressure on the roof shall be equal to the vertical uplift force determined in accordance with divided by the horizontal projected area of the roof of the rooftop structure and shall be considered to act in the upward direction.