R503.1.1

Section R503.1 is titled 'End joints' and covers the requirements for support of the short edges of lumber subflooring and when subflooring is not required. The requirement for the support of end joints of non-end-matched and end-matched lumber used as subflooring, and the allowance for not requiring subflooring is established. The purpose of this section is to prevent structural failure.

The model shows a partial floor section with end-matched lumber being joined not over the top of a floor joist, with each piece bearing on at least 2 floor joists. Since this lumber is 1" nominal thickness, is tongue-and-groove (including on the short edges), and is being applied perpendicular to the joists, it could be used as the final floor covering (though this is not commonly done).