Roof Deflection Limits

Typical deflection limits referenced in code books are l 360 l 240 or l 180.

Roof deflection limits.

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. Examples of code prescribed deflection limits and live load values are. In order to stay intact and in place a roof must be able to resist loads both permanent and temporary that are pushing. 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.

For the purpose of the determining deflection limits herein. The deflection of floor and roof assemblies shall not be greater than l 360 for plastered construction. Chapter 3 of the international residential code irc provides the maximum allowable deflection for a given structural member floor roof wall etc. And l 180 for unplastered roof construction.

Typically codes set deflection limits for roofs walls and floors. 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. Codes provide the maximum allowable deflection limits for floor and roof trusses which is based solely on the truss span. For floor trusses the deflection in inches due to live load cannot.

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. Roofs are under a lot of pressure. These limits are based on live loads and activities experienced in specific rooms of a house.

So these are the limits set by the code. D tl l 240. B for cantilever members l shall be taken as twice the length of the cantilever. These limit states are mathematic expressed as.

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. L 240 for unplastered floor construction. See the table below.

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. The code section on working load deflection states.