Floor Deflection Rating

What uncle dunc said.

Floor deflection rating.

The l 360 standard means that the floor should not deflect more than the span divided by 360. See the table below. Book has been around for ages and one you may find helpful. Note it gives the allowable deflection based on a fractional span quantity so a larger denominator will yield less deflection.

If we use the same joist total deflection will be 1 50 1 25 0 25. To provide higher quality floors for homeowners a deflection limit of l 480 is commonly used. In canada the building code includes limits on floor vibration. For example the maximum deflection for a joist span of 15 is 15 12 360 1 2.

Length in inches divided by 360 is the maximum allowable amount of floor deflection. Frequently there is misunderstanding regarding deflection between joists. The irc says that floors must deflect no more than 1 360 of the floor s span. Get yourself a copy of simplified engineering for architect and builders by parker ambrose published by john wylie and sons.

For example a floor with a span of 10 feet must deflect no more than 1 3 inch or 120 inches 360 inches. You also have options depending on the expected configuration of your solution. For example the allowable deflection of a 12ft span floor joist with plaster l 360 is 0 4 12ft divided by 360. For the 20ft floor joist example the new deflection limit is now 1 2inch.

Enter your floor joist information and then hit calculate deflection to find out your floor rating. Ft plus any long term deflection due to the weight of the floor. 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 calculator is designed to work with dimensional lumber only.

The deflection calculator provides several engineering specifications such as the moment of inertia and yield strength to determine deflection. Codes don t regulate floor vibration. Whether there will be one fixed end two fixed ends or the load will be supported on both ends. If that same joist had gypsum ceiling l 240 the allowable deflection is 0 6.

Now consider the same floor joist supporting stone tile flooring such that floor dead load is now 20 psf. The tj pro rating is based on satisfaction percentages of homeowners. Ilevel has taken this one step further by creating their tj pro rating. Divide the total span of the floor joists in inches by 360 to determine the maximum amount the floor can give in the middle under a live load of 40 lb sq.

If you have engineered truss or i beam type joists please do not use this calculator.