Laying ply sp101

I will be laying ply down to prepare for LVT. What do you use to secure the ply to the original floor which I believe is maybe chipboard. Thanks

 

Coil Nailer with ring shanked pins. Short of that, hammer and a pack of ring shanked nails. Stagger the joints and pin every 100mm

 

Or small screws. 18mm or 22mm

 

Would I have to use same number of screws as I would nails? Also do I need to leave an expansion gap for the ply or can it go right up to wall.

 

I always left a small gap away from the skirts. About 3mm.

Yes screw every 6” and 4” on the perimeter of each board