Floor Deflection Standard

For an older home the deflection usually exceeds the current code requirements.

Floor deflection standard.

Is assumed to be the dead load or the weight of the building materials themselves and 40 lb. Codes also specify how much floors are allowed to bend under load a measurement called a deflection limit. 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. Frequently there is misunderstanding regarding deflection between joists.

Many tile contractors can judge a floor s deflection by walking around. The l 360 standard means that the floor should not deflect more than the span divided by 360. Deflection for exterior walls with interior gypsum board finish shall be limited to allowable deflection of h 180. For example the allowable deflection of a 12ft span floor joist with plaster l 360 is 0 4 12ft divided by 360.

Refer to section r703 7 2 reason. The current combined row for floors and ceilings with plaster and stucco. 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. Similarly the allowable deflection for a criterium of l 240 would be 144 inches divided by 240 which is 0 6 inch.

Of that 10 lb. To calculate a specific value the tile council of north america tcna offers a standard formula. Is the live load or the weight of the furniture. 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.

See the table below. Note it gives the allowable deflection based on a fractional span quantity so a larger denominator will yield less deflection. This is intended to be an editorial clean up and not change any current requirements for deflection criteria. The irc says that floors must deflect no more than 1 360 of the floor s span.

For example a floor with a span of 10 feet must deflect no more than 1 3 inch or 120 inches 360 inches. Stiffness is measured by the floor s deflection under load.