Joists are covered by a layer (or double layer) of boards called SUBFLOORING. It usually consists of square-edge or tongue-and-grooved boards or plywood 1/2 to 3/4 in. thick that serve

Figure 6-19.-Typical floor framing with subflooring.

as a working platform and base for finish flooring (fig. 6-19). Sub flooring may be applied either diagonally (most common) or at right anglesto the joists. Diagonal subflooring permits finish flooring to be laid either parallel to, or, more commonly, at right angles to, the joists. The joist spacing should not exceed 16 in. O.C. when finish flooring is laid parallel to the joists or when parquet finish flooring is used.