Floor Stiffness 360 Or 480

Strength of a material is obviously important.

Floor stiffness 360 or 480.

The solution is to specify an upgrade to a lesser deflection than the code required l 360. Unlike stiffness live loads and dead loads are added together to determine minimum design values for strength. Floor beams commercial office institutional floor joists spans to 26 ft b ll 60 psf. Joists and rafters must be strong enough not to break when loaded.

That means l 360 is implied for the total load deflection and it will result in much better floor performance. So if you have a beam 20ft long the allowable deflection limit is 20ftx12in ft 240 1. 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. Bedrooms and habitable attic floors l 360 30 psf. The l stands for length. Please read everything on the attached photo below.

For l 480 deflection the maximum span drops to 15 feet 6 inches. L 360 60 psf ll 80 psf. Typically for better performing floors minimal defection is desired. Ask your building designer about the investment difference to increase stiffness to l 480 or even l 720.

L 300 girders spans to 36 ft b ll 60 psf. Applied load dead load a. L 360 ll 80 psf. To take weyerhaeuser s trus joist span tables as an example 17 feet 2 inches is the maximum span with an l 360 deflection ratio allowed by code for a floor that s framed with the company s 9 inch deep nominal 2x10 series 110 tji joists spaced 16 inches on center.

Chapter 3 of the international residential code irc provides the maximum allowable deflection for a given structural member floor roof wall etc. I prefer to go with a span chart that uses l 480 for the live load. The deflection for exposed ceiling beams at the roof is often allowed to be 50 to 100 greater l 240 or l 180. Looking for a wood floor which will give exemplary performance with a minimum of bounce.