A.Corresponding editor Paul Fisette responds: I would install the underlayment panels perpendicular to the joists, the same direction as the subfloor. It is a good idea to stagger the joints — both the end and edge joints — by at least 6 inches. Most handbooks do not require that you "hit" the underlying joists with the underlayment. Personally, I prefer to have the end-joint hit a joist, so I would offset the ends of the panels by 16 inches.

APA—The Engineered Wood Association has a good publication called The Design/Construction Guide: Residential & Commercial that has a lot of very good information about many floor, wall, and roof applications. The publication addresses recommended installation details, including nail spacing, for the installation of underlayment. To order the guide, call APA at 253/565-6600.