So I've been thinking of adding a hardwood floor in my dining room and hallway. This is what I know as of right now. I have Hemlock 2×10 Floor Joists spaced apart 16" OC that span 13 feet and the home was built in '71. The subfloor as it sits right now is 1/2" plywood with what seems to be 1/2" MDF or Particle Board nailed on top. I've noticed the floor is not perfectly level and might be due to the MDF warping and expanding from moisture. From what I've been researching it would be best to rip up the MDF (or Particle Board) and gluing the 3/4" plywood and screwing it down to the existing 1/2" plywood (not to the floor joists). Then lay down a vapor barrier and then the flooring at a right angle to the floor joists. Is this correct? I just want to get all of my ducks in a row before I go spend money.
Wood – Is this the correct approach for installing 3/4″ Hardwood floor
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Related Solutions
If possible, try framing out the edges. I would remove all of the existing sub floor (since it is particle board) and then add addition framing along the edges as needed for the new plywood. In cases where you can't meet a joist, go perpindicular and create a nice foundation for the floor to attach too.
I would make sure the floor has a firm foundation. It might be extra work to do it, but I would take those extra steps if possible.
It will create a mess if the particle board is not predrilled because the screws will at least break-out the backside of the particle board there by preventing the screw from ever drawing the PB flat against the plywood ... especially if the PB is not high density (heads will pull through) ... and especially if the screws are going into something as thin as 5/8" (low grade) subfloor grade plywood.
When predrilling, a depth stop will be essential to keep from drilling into the plywood because over-drilling by a mere 1/8" will leave less than 1/2" of plywood for the screw to grip. A small chunk of wood can be used as a positive (failsafe) depth stop. It'd be best to layout the joist locations on the 3/8" PB and aim the screws to grab into the joists.
If adhesive from a caulking gun is used, the floor will end up wavy, not flat, if you were to put a straight edge to it afterwards.
Regardless, I can't see the job coming out well using 3/8" particle board. Sorry for the pessimism. Is 3/4" not an option?
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Best Answer
I have seen 3/4" thick hardwood floors go over 1/2" subfloor with no problem. Your floor structure is plenty heavy to carry any load you apply to it. In many older homes (really old homes) there was no subfloor at all, and the floors held up very well.
Remove the layer of MDF, clean up the nails, and reset all the nails that are in the subfloor. This minimizes the chance of squeaks from the nails that may have risen up as the framing dried and shrunk. Add 1 5/8" screws at all the edges and 3 or 4 more spread across the center of the spans of all the plywood.
In my humble opinion, DO NOT use an underlayment foam under hardwood flooring. This is only intended for floating floors!!!!. The "give" the foam has, is asking for your floor to squeak!!! The only vapor barrier you need is a 5 lb. felt paper. It is much lighter and much thinner than roofing tar paper and will give the resistance the wood needs against moisture rising from below. This is what is used in all new floor applications. Sometimes, on occasion red rosin paper is used too, I believe it is error, it has no resistance to vapor permeability.
After this initial bit of prep, lay your new floor.