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Each portion of a roof shall be designed to sustain the load of rainwater that will accumulate on it if the primary drainage system for that portion is blocked plus the uniform load caused by water that rises above the inlet of the secondary drainage system at its design flow. The design rainfall shall be based on the 100-year hourly rainfall rate indicated in Figure 1611.1 or on other rainfall rates determined from
approved local weather data.
where:
| dh | = | Additional depth of water on the undeflected roof above the inlet of secondary drainage system at its design flow (i.e., the hydraulic head), in inches (mm). |
| ds | = | Depth of water on the undeflected roof up to the inlet of secondary drainage system when the primary drainage system is blocked (i.e., the static head), in inches (mm). |
| R | = | Rain load on the undeflected roof, in psf (kN/m2). When the phrase "undeflected roof" is used, deflections from loads (including dead loads) shall not be considered when determining the amount of rain on the roof. |
[P] FIGURE 1611.1 100-YEAR, 1-HOUR RAINFALL (INCHES) WESTERN UNITED STATES | For SI: 1 inch = 25.4 mm. |
| Source: National Weather Service, National Oceanic and Atmospheric Administration, Washington, DC. |
[P] FIGURE 1611.1‒continued 100-YEAR, 1-HOUR RAINFALL (INCHES) CENTRAL UNITED STATES | For SI: 1 inch = 25.4 mm. |
| Source: National Weather Service, National Oceanic and Atmospheric Administration, Washington, DC. |
[P] FIGURE 1611.1‒continued 100-YEAR, 1-HOUR RAINFALL (INCHES) EASTERN UNITED STATES | For SI: 1 inch = 25.4 mm. |
| Source: National Weather Service, National Oceanic and Atmospheric Administration, Washington, DC. |
[P] FIGURE 1611.1‒continued 100-YEAR, 1-HOUR RAINFALL (INCHES) ALASKA | For SI: 1 inch = 25.4 mm. |
| Source: National Weather Service, National Oceanic and Atmospheric Administration, Washington, DC. |
[P] FIGURE 1611.1‒continued 100-YEAR, 1-HOUR RAINFALL (INCHES) HAWAII | For SI: 1 inch = 25.4 mm. |
| Source: National Weather Service, National Oceanic and Atmospheric Administration, Washington, DC. |
Related Code Sections
Each portion of a roof shall be designed to sustain the load of rainwater that will accumulate on it if the primary drainage system for that portion ...
Number of plies if greater than one; 4. Required bearing widths; 5. Design loads as applicable, including; 5.1. Top chord live load; 5.2. Top chord dead load; 5.3. Bottom chord live load; 5.4. Bottom chord dead load; 5.5. Additional loads and locations; and 5.6. Environmental design criteria and loads (wind, rain, snow ...
The following terms are defined in Chapter 2: ALLOWABLE STRESS DESIGN. DEAD LOADS. DESIGN STRENGTH. DIAPHRAGM. Diaphragm, blocked. Diaphragm boundary. Diaphragm chord. ESSENTIAL FACILITIES. FABRIC PARTITION. FACTORED LOAD. HELIPAD. ICE-SENSITIVE STRUCTURE. IMPACT LOAD. LIMIT STATE. LIVE LOAD. LIVE LOAD (ROOF). LOAD AND RESISTANCE FACTOR DESIGN (LRFD). LOAD EFFECTS. LOAD FACTOR. LOADS. NOMINAL LOADS. OTHER STRUCTURES. PANEL (PART OF A STRUCTURE). RESISTANCE FACTOR. RISK CATEGORY. STRENGTH, NOMINAL. STRENGTH, REQUIRED. STRENGTH DESIGN. SUSCEPTIBLE BAY. VEHICLE BARRIER. NOTATIONS. D = Dead load. D i = Weight of ice in accordance with Chapter 10 of ASCE 7. E = Combined effect of horizontal and vertical earthquake induced forces as defined in Section 12.4.2 of ASCE 7. F = Load due to fluids with well-defined pressures and maximum heights. F a = Flood load in accordance with Chapter 5 of ASCE 7. H = Load due to lateral earth pressures, ground water pressure or pressure of bulk materials. L = Roof live load greater than 20 psf (0.96 kN/m 2 ) and floor live load. L r = Roof live load of 20 psf (0.96 kN/m 2 ) or less. R = Rain load ...
members supporting formed metal siding, the design wind load deflection shall not exceed l /90. For roofs, this exception only applies when the metal ...
shall be designed and constructed in accordance with strength design, load and resistance factor design , allowable stress design , empirical design or conventional construction methods, as permitted by the applicable material chapters. Lateral force-resisting systems shall meet seismic detailing requirements and limitations prescribed in this code and ASCE 7, excluding Chapter 14 and Appendix 11A, even when wind load effects are greater than seismic load effects . Buildings and other structures, and parts thereof, shall be designed and constructed to support safely the factored loads in load combinations defined in this code without exceeding the appropriate strength limit states for the materials of construction. Alternatively, buildings and other structures, and parts thereof, shall be designed and constructed to support safely the nominal loads in load combinations defined in this code without exceeding the appropriate specified allowable stresses for the materials of construction. Loads and forces for occupancies or uses not covered in this chapter shall be subject to the approval of the building official . Structural systems and members thereof shall be designed to have adequate stiffness to limit deflections and lateral drift. See Section 12.12.1 of ASCE 7 for drift limits applicable to earthquake loading. TABLE 1604.3 DEFLECTION LIMITS a, b, c, h, i CONSTRUCTION L S or W f D + L d, g Roof members: e Supporting plaster or stucco ceiling Supporting nonplaster ceiling Not supporting ceiling l /360 l /240 l /180 l /360 l /240 l /180 l /240 l /180 l /120 Floor members l /360 ‒ l /240 Exterior walls: With plaster or stucco finishes With other brittle finishes With flexible finishes ‒ ‒ ‒ l /360 l /240 l /120 ‒ ‒ ‒ Interior partitions: b With plaster or stucco finishes With other brittle finishes With flexible finishes l /360 l /240 l /120 ‒ ‒ ‒ ‒ ‒ ‒ Farm buildings ‒ ‒ l /180 Greenhouses ‒ ‒ l /120 For SI: 1 foot = 304.8 mm. a. For structural roofing and siding made of formed metal sheets, the total load deflection shall not exceed l /60. For secondary roof structural members supporting formed metal roofing, the live load deflection shall not exceed l /150. For secondary wall members supporting formed metal siding, the design wind load deflection shall not exceed l /90. For roofs, this exception only applies when the metal sheets have no roof covering. b. Flexible, folding and portable partitions are not governed by the provisions of this section. The deflection criterion for interior partitions is based on the horizontal load defined in Section 1607.14. c. See Section 2403 for glass supports. d. The deflection limit for the D+L load combination only applies to the deflection due to the creep component of long-term dead load deflection plus the shortterm live load deflection. For wood structural members that are dry at time of installation and used under dry conditions in accordance with the ANSI/AWC NDS, the creep component of the long-term deflection shall be permitted to be estimated as the immediate dead load deflection resulting from 0.5 D . For wood structural members at all other moisture conditions, the creep component of the long-term deflection is permitted to be estimated as the immediate dead load deflection resulting from D . The value of 0.5 D shall not be used in combination with ANSI/AWC NDS provisions for long-term loading. e. The above deflections do not ensure against ponding. Roofs that do not have sufficient slope or camber to ensure adequate drainage shall be investigated for ponding. See Section 1611 for rain ...
