How to Underlay Vinyl

Written by jonah morrissey | 13/05/2017

Before you install vinyl floor covering, you need to create a smooth floor surface for it. This surface is called underlay, and comes in 1/4-inch thick plywood panels. Because vinyl flooring is not as thick as hardwood, it is essential to have a seamless surface below it. Take your time installing the underlay to make sure this surface is completely flat with no depressions or ridges. The result will be an easy vinyl installation and a long-lasting floor surface.

Slide a flat pry bar underneath the moulding at the base of each wall in the room and gently pry it up from the floor. Set the moulding aside in a safe place for reinstallation.

Lay out the plywood panels on the floor, butting them tightly together. Measure the spaces on the floor that are too small to fit an entire panel.

Measure and mark additional underlay panels to the dimensions required to fit the remaining floor spaces.

Use a power saw to cut the panels to the required dimensions. If you elect to use a table saw, slide each panel through the saw with its face resting flat on the table. Guide the panel along in a steady motion until the each cut is complete.

Lay the cut sections of underlay into the appropriate spaces on the floor.

Drive the finishing nails through the underlay around the perimeter of each panel spaced every six to eight inches.

Spread a coat of floor levelling compound over the seams of the underlay panels using a 6-inch drywall knife. This helps create a uniform surface for the vinyl. Allow the levelling compound to dry according to the manufacturer's directions.

Sand the levelling compound so that the transition between panels is completely smooth using a 100-grit sanding pad. Use a shop vacuum to remove the dust created by sanding.


Use a nail gun to make the installation of the underlay more efficient.


Wear eye protection when cutting and installing underlay.

Tips and warnings

  • Use a nail gun to make the installation of the underlay more efficient.
  • Wear eye protection when cutting and installing underlay.

Things you need

  • Flat pry bar
  • Plywood underlay panels, 4-feet-by-8-feet, 1/4-inch wide
  • Tape measure
  • Pencil
  • Power saw
  • Hammer
  • 3d finishing nails
  • Levelling compound
  • 6-inch-wide drywall knife
  • 100-grit sanding pad
  • Shop vacuum

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