Roof Deflection Limits

In any given room the framing in the ceiling is really just the framing for the floor of the room above it or for the roof.

Roof deflection limits.

Roofs are under a lot of pressure. The international code council icc is a non profit organization dedicated to developing model codes and standards used in the design build and compliance process. B for cantilever members l shall be taken as twice the length of the cantilever. D tl l 240.

And l 180 for unplastered roof construction. The code section on working load deflection states. For aluminum structural members or panels used in roofs or walls of sunroom additions or patio covers not supporting edge of glass or sandwich panels the total load deflection shall not exceed l 60. Load limits on the roof of a building.

Bedrooms and habitable attic floors l 360 30 psf. Note it gives the allowable deflection based on a fractional span quantity so a larger denominator will yield less deflection. So these are the limits set by the code. Typically codes set deflection limits for roofs walls and floors.

These limits are based on live loads and activities experienced in specific rooms of a house. Codes provide the maximum allowable deflection limits for floor and roof trusses which is based solely on the truss span. Typical deflection limits referenced in code books are l 360 l 240 or l 180. Generally for roof trusses the deflection in inches due to live load cannot exceed the span in inches divided by 240 l 240 and due to total load l 180.

Examples of code prescribed deflection limits and live load values are. This simplistic criteria puts a limit of the span divided by 360 on the incremental deflection due to live or transient load only and a limit of the span divided by 240 on deflection under total load. For the purpose of the determining deflection limits herein. L 240 for unplastered floor construction.

See the table below. D ll l 360. The international codes i codes are the widely accepted comprehensive set of model codes used in the us and abroad to help ensure the engineering of safe sustainable affordable and resilient structures. For floor trusses the deflection in inches due to live load cannot.

These limit states are mathematic expressed as. Chapter 3 of the international residential code irc provides the maximum allowable deflection for a given structural member floor roof wall etc.