We used the joint p.
How to fasten several sheets of plywood.
Drive the screws through the plywood into the frame countersinking the heads below surface.
It sounds like you re planning to stack two sheets together.
This will give you tons of contact with long grain to create a really strong glue joint.
Screws fasten the scab to the other two pieces in addition to the glue.
Insert a drill bit into the sleeve and drill the hole at an angle through the end to penetrate through the face.
Fit the jig over the end of one piece of plywood to position the sleeve.
If you use adhesive for the underlayment you can get away with fasteners every 8 using ring shanked nails.
In this video you will get how to join two plywood pieces together side by side for utilizing the wastage or cutting part of the plywood.
Using my experience i would fasten the underlayment with adhesive and 7 16 inch crown staples every 6 inches driven with a pneumatic stapler.
For the 1 2 underlayment ideally you want to screw every 6 all across the panel.
After adding glue the two pieces are screwed together with glue and optionally bar clamps.
Wood glue on the scab face and on the edges that meet strengthen the joint.
A 90 degree connection places the glued edge of.