I am about to lay some 3/4" solid oak hardwood in my living room. I removed the carpet and fiberboard underlayment. What I found was 1/2" plywood (not tongue and groove) as my subfloor, joists are 16"o/c. I definitely will be adding to the 1/2" but have a couple of questions. I did search around the internet but had a hard time finding the answers to my specific situation.

1. I plan on installing 23/32" second layer. Does it need to be tongue and groove?

2. Do I need to make sure I don't hit a joist when I screw it down? Or can I hit the joist to make one uniform subfloor vs. a subfloor and underlayment.

3. I am reading a lot of conflicting info on whether I should install plywood or OSB (Advantech).


4. If I have any week spots in the 1/2" should I replace that section or will the 23/32" second layer negate the need to replace the week section of 1/2"



Thanks for your help.

Probably everyone who has a garden and a place to relax and unwind. The wooden floor is a good thing for a place like this because it is comfortable outside and comfortable, and adds a bit of heat.

Another layer of plywood with the edges glued before fastening it down following the recommended nailing schedule will be better than T&G on the edges.
One-half inch plywood used to be "good enough" to nail 3/4 inch flooring.
I've seen flooring that has been down over 30 years and has no problems. Maybe the floor lengths were longer then and short boards were used for starting and finishing rows, not in the field. Now you will get lots of short boards which do not add as much stiffness.