DIY Network

How to Prep a Subfloor

It's important to prepare a subfloor properly so there are no gaps or cracks in it.

More in Floors

roll out underlayment in strips on top of subfloor
  • Time

    Under Half Day

  • Price Range

    $50 - $100

  • Difficulty

    Easy to Moderate


Step 1: Level the Seams

Make sure all the nails are below the surface. Make sure the seams are level. If they're not, belt sand off the high spots.

sand high spots on subfloor

Step 2: Fill the Gaps

Fill the gaps that are larger than 1/8" with skim coat. You will want to work fast because this is a gypsum-based skim coat and will dry within five minutes.

Step 3: Apply the Skim Coat

Work in the skim coat and feather the edges. Go back over it with a large mudding (drywall) knife for a smooth finish. After it dries, knock down the high spots with a random orbital sander.

use self leveling compound to smooth out subfloor

Step 4: Attach the Rosin Paper

Cover the subfloor with rosin paper to create a moisture barrier between the subfloor and the finished floor and will smooth out any imperfections. Tack it down with a hammer stapler.