When a 4x8 sheet of 15/32 plywood is laid lengthwise on 1x4 lath (the lath is running perpendicular to the rafters) is it permissible for the long edge of the plywood sheet not to be supported by lath directly below the edge? Is there an allowable amount of overhang?
Here is a cross-section of what I mean, where
XXXXXX is the 4' edge of the plywood sheet and
[p] is a purlin:
|????| XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX [p] [p] [p] [p] [p] ^
If overhang is allowed, what is the maximum length of the overhanging plywood section marked with the question marks, where where is no purlin directly beneath the long edge?
If overhang is not allowed, additional lath would have to be added below the long edge of the sheet as a fastening surface, at the location marked by
P.S. I've found an APA document (Bulletin P300C) on the subject of decking over lath; it shows the addition of lath to support the edge. "Panel edges should not be cantilevered". Here's a screen cap of the relevant drawing (the document requires a login/registration and cannot be accessed via a URL):