What Is Floor Deflection

For example the allowable deflection of a 12ft span floor joist with plaster l 360 is 0 4 12ft divided by 360.

What is floor deflection. If the span of the joists is 10 feet between supports then the deflection should not be more than 1 3 between the center and the end. The longer the beam gets the more that it can bend and the greater the deflection can be. Deflection or bounciness can cause tiles and grout to crack or come loose and the tolerance depends on what type of tile is being installed. In engineering deflection is the degree to which a structural element is displaced under a load due to its deformation it may refer to an angle or a distance.

If that same joist had gypsum ceiling l 240 the allowable deflection is 0 6. For example a floor joist spanning 20ft 240 inches a deflection limit of 2 3inch for live loads and 1inch for total loads. A l 360 deflection means that the length of the floor span divided by 360 equals what the allowable bending is of the floor with out damage to the tile instllation. For new home builders a squeaky or bouncy floor is a sign of substandard or code minimum construction practices the effect of which can erode their reputation for delivering comfortable quality.

The deflection distance of a member under a load can be calculated by integrating the function that mathematically describes the slope of the deflected shape of the member under that load. However by inspecting our formulas we can also say that the beam s length also directly affects the deflection of the beam. Got bounce appeared in the august 2012 issue of prosales and dealt with mitigating floor deflection in new home construction. In this video i explain why the floor and furnishings can shake when you walk by them.

All floors deflect or move to some extent but if. The reason being is what we call floor deflection. In order to build. The l 360 standard means that the floor should not deflect more than the span divided by 360.

Note it gives the allowable deflection based on a fractional span quantity so a larger denominator will yield less deflection. How to fix floor deflection for ceramic tile. Frequently there is misunderstanding regarding deflection between joists. This is the maximum deflection the designer should meet but it is only a minimum requirement.

See the table below. The formulas show that the stiffer the beam is the smaller its deflection will be. Because ceramic floor tile is rigid and unforgiving it needs a structurally sound immobile base. Floor deflection test hi molly try to determine the span of the floor joists that is how far apart are the supported ends of the 2 x 8 joists.

This is the second of two articles on proper floor framing.