I HAVE AN EXISTING CARPETED FLOOR THAT CONSISTS OF A SUB FLOOR OF 1/2″ CDX PLYWOOD AND 5/8″ PARTICLE BOARD ON TOP OF THAT, THE FLOOR JOISTS ARE ON 16″ CENTERS, I WOULD LIKE TO PUT 3/4″ HARDWOOD FLOORING DOWN, IF I REMOVE THE PARTICAL BOARD (TO OBTAIN CORRECT FLOOR HEIGHT) IS THE 1/2″ PLYWOOD ENOUGH UNDER THE HARDWOOD ???? WHAT SHOULD I DO??
Most assuredly you must remove the particle board. It is the poorest of nailing surfaces.
Add another layer of 1/2″ plywood, and this will be plenty. Be sure to fasten this layer with 3″ spiral nails nailed into the joists. Apply squiggles of a urethane construction adhesive on the old plywood at the joist and between the joists. This will prevent the layers of plywood from squeaking at the nail shafts. A thinner plywood will not provide enough structure.
Be sure you use proper flooring NAILS, not staples for the new hardwood. Read my article about this in the Floored News section (Primatech Article).
As always your Most humble servant, Joseph, the Wood Floor Doctor.