Roof Deflection Limits

Typically codes set deflection limits for roofs walls and floors.

Roof deflection limits.

See the table below. So these are the limits set by the code. Codes provide the maximum allowable deflection limits for floor and roof trusses which is based solely on the truss span. L 240 for unplastered floor construction.

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. In order to stay intact and in place a roof must be able to resist loads both permanent and temporary that are pushing. 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.

For floor trusses the deflection in inches due to live load cannot. D tl l 240. B for cantilever members l shall be taken as twice the length of the cantilever. Note it gives the allowable deflection based on a fractional span quantity so a larger denominator will yield less deflection.

Roofs are under a lot of pressure. These limits are based on live loads and activities experienced in specific rooms of a house. Chapter 3 of the international residential code irc provides the maximum allowable deflection for a given structural member floor roof wall etc. 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.

The code section on working load deflection states. And l 180 for unplastered roof construction. Typical deflection limits referenced in code books are l 360 l 240 or l 180. Bedrooms and habitable attic floors l 360 30 psf.

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. 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. Load limits on the roof of a building. The deflection of floor and roof assemblies shall not be greater than l 360 for plastered construction.

These limit states are mathematic expressed as. Living room floors l 360 40 psf.