R301.7

Section R301.7 is titled 'Deflection' and covers the requirements for the maximum amount of bend of a structural member under the maximum design load. Roofs, ceilings, walls (both interior and exterior), floors, and lintels are limited in how much they can bend in accordance to Table R301.7.

The model shows a floor joist (colorized for clarity) which is being loaded to the maximum amount of deflection. (The adjacent floor joist is not being loaded and is in a contrasting color to provide visual clarity of the deflecting floor joist.) Per the third row in table R301.7, 120" span length/360 = 1/3" allowable deflection. Of course this model is only showing a single member to explain the concept of this section of the code. In reality a floor assembly will include spaced floor joists with a floor covering acting together to resist deflection.