Ft plus any.
Floor deflection standard.
Codes also specify how much floors are allowed to bend under load a measurement called a deflection limit.
The standard load designed for most residential floors to support is 50 lb.
Refer to section r703 7 2 reason.
This is intended to be an editorial clean up and not change any current requirements for deflection criteria.
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.
See the table below.
Stiffness is measured by the floor s deflection under load.
The l 360 standard means that the floor should not deflect more than the span divided by 360.
For example a floor with a span of 10 feet must deflect no more than 1 3 inch or 120 inches 360 inches.
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.
Deflection for exterior walls with interior gypsum board finish shall be limited to allowable deflection of h 180.
If that same joist had gypsum ceiling l 240 the allowable deflection is 0 6.
For an older home the deflection usually exceeds the current code requirements.
Note it gives the allowable deflection based on a fractional span quantity so a larger denominator will yield less deflection.
Many tile contractors can judge a floor s deflection by walking around.
Is assumed to be the dead load or the weight of the building materials themselves and 40 lb.
Is the live load or the weight of the furniture.
Similarly the allowable deflection for a criterium of l 240 would be 144 inches divided by 240 which is 0 6 inch.
Frequently there is misunderstanding regarding deflection between joists.
Of that 10 lb.
If the floor deflects more than the 0 4 inches or 0 6 inches the floor is deflecting more than what the standard allows and does not meet code.
For example the allowable deflection of a 12ft span floor joist with plaster l 360 is 0 4 12ft divided by 360.
