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 LIMITSa, b, c, h, i
For SI: 1 foot = 304.8 mm.
TABLE 1604.3 DEFLECTION LIMITSa, b, c, h, i
| CONSTRUCTION | L | S or W f | D + Ld, 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.
- 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.
- 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.
- See Section 2403 for glass supports.
- 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 0.5D. 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 0.5D shall not be used in combination with ANSI/AWC NDS provisions for long-term loading.
- 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 and ponding requirements and Section 1503.4 for roof drainage requirements.
- The wind load is permitted to be taken as 0.42 times the "component and cladding" loads for the purpose of determining deflection limits herein. Where members support glass in accordance with Section 2403 using the deflection limit therein, the wind load shall be no less than 0.6 times the "component and cladding" loads for the purpose of determining deflection.
- For steel structural members, the dead load shall be taken as zero.
- For aluminum structural members or aluminum panels used in skylights and sloped glazing framing, roofs or walls of sunroom additions or patio covers not supporting edge of glass or aluminum sandwich panels, the total load deflection shall not exceed l/60. For continuous aluminum structural members supporting edge of glass, the total load deflection shall not exceed l/175 for each glass lite or l/60 for the entire length of the member, whichever is more stringent. For aluminum sandwich panels used in roofs or walls of sunroom additions or patio covers, the total load deflection shall not exceed 1/120.
- For cantilever members, l shall be taken as twice the length of the cantilever.
The deflections of structural members shall not exceed the more restrictive of the limitations of Sections 1604.3.2 through 1604.3.5 or that permitted by Table 1604.3.
The deflection of reinforced concrete structural members shall not exceed that permitted by ACI 318.
The deflection of steel structural members shall not exceed that permitted by AISC 360, AISI S100, ASCE 8, SJI CJ, SJI JG, SJI K or SJI LH/DLH, as applicable.
The deflection of masonry structural members shall not exceed that permitted by TMS 402/ACI 530/ASCE 5.
The deflection of aluminum structural members shall not exceed that permitted by AA ADM1.
The deflection limits of Section 1604.3.1 shall be used unless more restrictive deflection limits are required by a referenced standard for the element or finish material.