Concrete Floor Deflection

If that same joist had gypsum ceiling l 240 the allowable deflection is 0 6.

Concrete floor deflection.

Deflection calculations it is backed by site based research. The concrete society publication. For example the allowable deflection of a 12ft span floor joist with plaster l 360 is 0 4 12ft divided by 360. This rigorous method is described in greater detail elsewhere e g.

The australian standard as 3600 2001 recommends a limit of l 250 table 1. It covers the consideration of crack formation and its impact on a concrete floor s deflection a critical consideration for conventionally reinforced slabs. Got bounce appeared in the august 2012 issue of prosales and dealt with mitigating floor deflection in new home construction. Per aci 117 these measurements are to be taken at a maximum of 72 hours after the concrete has been poured ie prior to shoring being removed.

See the table below. The concrete structures code limits the maximum mid span deflection of a beam spanning either between columns or in a two way beam system between its supporting beams. Design issues a few years ago floors we r e de signed using astm a36 steel 36 000 psi yield strength and al. To minimize floor leve l n e s s p r oblems in composite constru c tion both the designer and con t r actor should be aware of design and construction decisions that af fect deflection.

Crack width calculation where applicable is also discussed. Curvature in a simply supported slab. A comparative evaluation of. Note it gives the allowable deflection based on a fractional span quantity so a larger denominator will yield less deflection.

Detailed numerical examples illustrate the application of each of the methods presented. The main reason these are spec d is for requirements of the flooring. This difference in the values of modulus of elasticity shows that concrete can only withstand a small amount of deflection and will experience cracking sooner than steel. In our concrete specifications we indicated required f f and f l numbers for floor flatness and levelness.

This is the second of two articles on proper floor framing. Concrete structures codes also recommend limits for the calculated total deflection of floors.