How to Prep Subfloor for Hardwood

How to Prep Subfloor for Hardwood

Wood floors are as beautiful as they are durable,
and installing it yourself can save money. BUT, you need to prep your subfloor, or your
new flooring could have problems. We’ll show you the steps to prep a plywood subfloor. First you need to how much flooring and materials
you’ll need. Measure the room length times width to calculate the square footage. Add
about 10% for mistakes or warped boards. Next remove the baseboards, carpet, and tack
strips. If you have vinyl, you can install certain flooring right over it. No matter what type of flooring you install
your subfloor has to be: clean, dry, level, and structurally sound.
For glue down applications, you need to remove any wax, paint, adhesives, or oils with a
sander. For floating and nail down floors you just
need to clean up dust and debris. What about odors from pet stains? Well, the
best approach is to use a stain remover then cover it with a primer sealer. But keep in
mind, some glue down adhesives won’t adhere to the sealer, so check the instructions. After you’ve cleaned your floor check the
moisture level. A simple moisture meter will work. Just press the pins into your subfloor
and check the reading. Your flooring manufacturer’s instructions will list acceptable readings.
If your moisture levels are too high, call a pro for help.
Oh, when working on plywood over concrete, check the levels of both floors. After the moisture tests, check that the floor
is level. It shouldn’t vary more than 3/16-inch every 10-feet. Sand any high spots, and fix
low spots according to your floor type. Typically, on glue down and floating floors you can apply
leveling compound. For nail down floors you can repair by reinforcing the joists, or building
up the low spots with 15-pound felt or shims. Your subfloor also needs to be strong and
structurally sound. Fix loose or creaky boards with wood or decking screws. Of course any
major damage will need to be repaired too. One more note for subfloor repairs. Flooring
typically looks best running along the longest wall in the room, BUT it should be perpendicular
to the floor joists. If it won’t be, you can add another plywood layer to strengthen
the floor. Next, prep the doorways. Stack a piece of
flooring on the underlayment and cut door casings about 1/16-inch above with a jamb
saw. For doors, remove them and cut about 1/8-inch above. When your subfloor is in good shape, you can
put down the underlayment. The type depends on your flooring installation. For nailing
solid hardwood or stapling engineered, go with felt paper or Grade D craft paper. Roll
it out, leaving the underlayment long at the ends–you’ll trim it after you’ve installed
the floor. Overlap the seams about 6-inches, and staple down.
For floating engineered, locking, or laminate, use a 2-in-1 or 3-in-1. Typically they have
self-adhesive seams to join the pieces together. For glue down floors, the moisture barrier
is usually part of the adhesive. Some products even have the underlayment pre-attached,
but you might still need a moisture barrier. One other thing: some engineered, locking,
and laminate floors can go right over vinyl as long as it’s not two layers thick. Next step is to mark a starting line square
to the room walls. However, many walls are bowed or out of square, so here’s what you
do. Mark the center of each wall and snap lines
between. Then measure from the center to the starting wall, subtract the expansion gap,
and mark this distance at the ends. Snap a line between to get a straight line against
the wall. Now your subfloor is prepped. For more great ideas and how-to’s, go to or click subscribe. Next, learn how to install your flooring.

13 thoughts on “How to Prep Subfloor for Hardwood

  1. Can a locking floating engineered hardwood floor be installed over an existing glued down engineered hardwood floor (glued to the concrete slab).

  2. You did not mention that OSB subfloors (show in the video) should be overlayed with 1/4" – 3/8" plywood when installing solid hardwood so that the nails hold better. From the research I've done, OSB by itself will not hold the nails tight over time.

  3. The felt paper for build up on low spots is a very interesting idea. Do you have another video going into detail about this?

  4. Hi, I saw that Lowes recommended roofing felt. Is there any concerns I should have , a flooring company used roofing felt from United Roofing felt company (its basically all the same stuff) ,it had a California cancer sticker on.I realize everything in California causes cancer. Basiclly I'm asking is there any concerns like with gassing off or other chemical issues with air quality having roofing felt inside your home since its made to be outside Any help would be highly appreciated .Thank you

  5. Plywood sub floor is not needed. Apply 3/4" solid hardwood flooring right over the floor joists. Ask any carpenter from the 1920's!

  6. Any underlayment recommendations for sound insulating understand for 3/8" nail-in solid hardwood flooring? Only recommendation I see is the 15lbs black paper and that's moisture barrier only.

  7. can I use padding over the subfloor and staple down engineered wood floor through the padding into the subfloor with no vapor barrier? or even though I'm using pad I still need to use the paper like vapor barrier?

  8. 1. If I use Plytanium 23/32 CAT PS1-09 Tongue and Groove Pine Plywood Subfloor (Item # 12249) from Lowes directly over the joists, would I need a 2nd layer of plywood on top if installing a waterproof LVP that has built-in-underlayment? (It will be across reinforced joists in a laundry room & bathroom- supporting laundry appliances & a bathtub).
    2. Can I paint those sheets with something like Killz to protect them from moisture & mold?
    3. Is there anything I should put across the seams (or 1/8" expansion gaps between the subfloor seams) or would it be unlikely to cause problems for vinyl plank?

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