Floor Stiffness 360 Or 480

The solution is to specify an upgrade to a lesser deflection than the code required l 360.

Floor stiffness 360 or 480.

L 360 60 psf ll 80 psf. Unlike stiffness live loads and dead loads are added together to determine minimum design values for strength. And since it is small i will leave the source for where it is found here 1. For this reason i don t recommend using a span chart for any kind of floor member that uses l 360 as the deflection criteria.

A general rule for limiting deflection of simple spans is that the deflection should not exceed the span in inches divided by 360 max d l 360. So if you have a beam 20ft long the allowable deflection limit is 20ftx12in ft 240 1. Floor beams commercial office institutional floor joists spans to 26 ft b ll 60 psf. Bedrooms and habitable attic floors l 360 30 psf.

For l 480 deflection the maximum span drops to 15 feet 6 inches. Chapter 3 of the international residential code irc provides the maximum allowable deflection for a given structural member floor roof wall etc. The deflection for exposed ceiling beams at the roof is often allowed to be 50 to 100 greater l 240 or l 180. I prefer to go with a span chart that uses l 480 for the live load.

L 360 ll 80 psf. Applied load dead load a. Strength of a material is obviously important. Looking for a wood floor which will give exemplary performance with a minimum of bounce.

Ask your building designer about the investment difference to increase stiffness to l 480 or even l 720. Joists and rafters must be strong enough not to break when loaded. L 300 girders spans to 36 ft b ll 60 psf. Increased floor stiffness is desired used with permission.

Attic floors with limited storage l 240 10 psf. The amount of flex depends on the magnitude of the load applied span of the member and stiffness of the member. Please read everything on the attached photo below. That means l 360 is implied for the total load deflection and it will result in much better floor performance.