What Is Floor Deflection

In this video i explain why the floor and furnishings can shake when you walk by them.

What is floor deflection.

For floor joists a live load deflection limit of l 360 and a total load deflection limit of l 240 must be met. 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. However by inspecting our formulas we can also say that the beam s length also directly affects the deflection of the beam. For example the allowable deflection of a 12ft span floor joist with plaster l 360 is 0 4 12ft divided by 360.

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. This is the second of two articles on proper floor framing. In order to build. The reason being is what we call floor deflection.

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. The longer the beam gets the more that it can bend and the greater the deflection can be. See the table below. How to fix floor deflection for ceramic tile.

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. Note it gives the allowable deflection based on a fractional span quantity so a larger denominator will yield less deflection. If that same joist had gypsum ceiling l 240 the allowable deflection is 0 6. Frequently there is misunderstanding regarding deflection between joists.

Got bounce appeared in the august 2012 issue of prosales and dealt with mitigating floor deflection in new home construction. 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. Because ceramic floor tile is rigid and unforgiving it needs a structurally sound immobile base. The l 360 standard means that the floor should not deflect more than the span divided by 360.

The formulas show that the stiffer the beam is the smaller its deflection will be. For instance ceramic tile can withstand more deflection than natural stone. 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 example a floor joist spanning 20ft 240 inches a deflection limit of 2 3inch for live loads and 1inch for total loads.

This is the maximum deflection the designer should meet but it is only a minimum requirement.