Using 3/8 sanded plywood 4x8 panel over pine strip floor. 1

Purchased pl 400 sybfloor glue in the regular 10 oz tube 12 pack figure a tube per panel.

Plan is to use glue and staples

Questions:

What size gap between wall and fixed objects (vents etc)?
What size gap between plywood sheets if necessary?
What size crown staple?
Glue Pattern to put on backside?
Staple pattern or placement?

Thank you!

Are you planning to lay a hardwood floor over the plywood underlayment?
You may use the same staples to fasten the ply down. The staples will be ½ inch crown, 2 inches long. Take the foot off the stapler and just go straight down, instead of at the 45 angle. Use the underlayment nailing schedule, 6 inches at perimeter and 8 inches in field.
The glue helps, but you will need to have a clean sub-floor for it to stick.
A quarter inch bead of glue every foot and within an inch of the edge should hold well.
The ply needs to have an eighth inch between panels and obstructions.

If you are planning on installing a hardwood floor over the layer of plywood, we believe that all great flooring installations start with a solid subfloor. The PL subfloor adhesive is definitely the right place to start. Whatever you use as general "pins," whether it be staples or nails, I'd have to suggest you add screws to each sheet as well. The staples will hold the plywood in place, but expansion/contraction causes the wood to move around them, eventually causing squeaking and unwanted movement. To ensure you have a solid subfloor for whatever material you are planning to install over it, place screws along the beams to compress all the layers of the subfloor together. Over time, the screws hold up much better, eliminating squeaking and movement, ensuring a solid subfloor.

To help with squeaking, which usually comes from the sub-floor not being installed very well, you should use the stapler to fasten the sub-floor to the joists. Old T&G flooring is only fastened on one side of each plank. If you can find the floor joists going across the floor, be sure to fasten the old pine to the joists with the 2 inch staples, before you add the plywood. Sub-floor adhesive is made to be able to flex with sessional changes in the wood dimension. The stapling will hold the plywood until the glue dries.