Sub Floor Question

Q: I recently removed the carpeting on my 1929 year old floor with the hopes of refinishing the floors but with the condition of the wood, I decided to replace. Now the 2 1/2″ planks are placed directly across the joist so I don’t really have a subfloor. I plan to lay a 1/4″ or 1/2 ” plywood on top the old wood and lay out my new 3/4″ or 3/8″ solid wood floor.
Can you tell me if this is a good plan or tell me how I should go about this? The current floor seems flat as for as I checked with a level just severely damaged.
Thanks
Csam
A: I would suggest removing the old flooring, especially if it is making any noise whatsoever when walked over. There are two reasons why I suggest taking this course of action. The primary reason is that you can use thicker plywood as a subfloor – 3/4″ being the preference here. The second reason is that with older floors, especially those already making noise, they tend to transfer this noise directly through any new material installed over it, and later on this is nearly impossible to fix without removing everything.
Now as far as installing the new plywood, you will want to stagger the sheets in order to make the most effective and stable subfloor. This means that each joint or area where the sheets of plywood meet will be staggered so that a single seam does not cross the entire floor in both directions. The easiest set up for staggering plywood involves the use of 4′ x 8′ plywood. Lay your first row of plywood, then much like flooring, cut one of the 4′ x 8′ pieces of plywood in half, lay the 4′ x 4′ square as the beginning or row two, followed by 4′ x 8′ sheets for the remainder. Alternate like this for every two rows and you will have a nicely staggered subfloor laid out. Also ensure to leave a 1/8″ gap between the sheets of plywood to allow for some expansion and contraction of the subfloor.
Although this seems like a bit more work, it is the best way to ensure you have a flat and stable subfloor ready for a brand new floor. As far as the old flooring is concerned, there is a market out there for reclaimed flooring from specific decades – so there is a chance that your “old flooring” will be someone’s brand new dream floor. Although it has some damage there are folks who work around this in order to get a floor that is to the era of the home they wish to create.