Framing and Sub-Flooring - subfloor over soft wood.

I am installing ½ “plywood sub floor to old ¾”pine planks. The pine planks are soft, and the screws won’t bite when I do the field. I had no problem screwing the joists. I need advice on what to use on the field. .

What type screws are you using? I would use powder coated decking screws with a torx head, 2" long (2 1/2 or 3 for joist). Just how soft is soft? You may have to replace it as well if it is that soft. I really feel it is your fastener choice, however.

Thanks for your help Chandler; you have always given me good advice. You, along with other members have made it possible for me to do these projects. I’m just a knucklehead here, but my wife thinks I’m a hero when I finish out a new project for her and the kids.

I used 1 3/4 “sub floor screws to repair, and re-secure parts of the old ¾” planks, no
Problem there because I’m securing them into the joist. I used 21/2” multi purpose screws to secure the ½” plywood. No problem there when I secures the plywood to the joist. I used multi purpose screws because Menards only has 1 3/4” sub floor screws. I am trying to use 1” multi purpose screws to secure the field, because it’s my understanding that you don’t want the screw to go all the way through the layers of wood. A co-worker of mine thinks it could be the screws removing too much material as they are being screwed in; leaving nothing to grab. If I keep trying, I can get these screws to bite, but I end up with Swiss cheese sub floor. Am I correct with NOT selecting a screw that goes all the way through the floor? I will take your advice and use the coated deck screws, for the joists, but my main problem is the field. ,,, I’m putting wide plank hardwood that’s ¾” thick on this floor. It’s been suggested to me to use coated staples. I don’t trust ring shank nails.

I hate to do this, but I don't think the 1/2" plywood will be sufficient enough for the stability of your hardwood flooring. How far along are you? Can you install 3/4" Advantech instead? You want really good support for your flooring. I think, also, just the opposite of your friend. I don't think the screws you are using are aggressive enough to bite into the wood below. Your threads may be too close to the shaft. You will want a screw with a standout thread....course.

I used ½ “plywood over very old ¾” hardwood, and installed a hickory floor in the kitchen. That was three years ago, and it’s still good. I was thinking about ¾” plywood, but the new floor would be ¼” higher than the kitchen. Is it possible to join the floors and make them look good? I haven’t started yet, or purchased materials. I guess I’m going to have to try different screws .