Install Plywood Underlayment for Vinyl Flooring
There are plenty of reasons to install sheet vinyl flooring, not the least of which is cost savings over other flooring materials. Vinyl flooring is available in a huge number of patterns and colors, is easy to clean and is softer to walk on than most other hard surfaces. Because you can install sheet vinyl over existing vinyl, it offers the option of changing design without breaking the bank.
Vinyl flooring is usually not installed directly over the subfloor in residential applications. In most cases 4-by-8-foot sheets of particle board or plywood must be installed in preparation for the vinyl floor install.
One of the big considerations when installing different types of flooring in the home is getting the finished elevations to match. Cement board, thinset and tile add up to about 5/8 inch. Traditional hardwood flooring is 3/4-inch thick and carpet with pad is usually between 5/8 and 1 inch, depending on the type. Sheet vinyl, however is only about 1/16-inch thick. It needs to be built up to the same elevation of the other flooring types in the house. The thinness and softness of sheet vinyl requires that it be installed on a surface that is very flat and smooth. Installing underlayment in the vinyl areas supplies the elevation, smoothness and levelness necessary for the proper installation of vinyl floors.
One common underlayment for vinyl floors is 1/2-inch particle board. It’s inexpensive, flat, smooth and bonds well to the vinyl adhesives. On the downside, particle board underlayment has very little structural strength. In fact it must be supported by a strong subfloor with limited gaps and it can bridge only small holes.
Another weakness of particleboard underlayment is that it really doesn’t like water. It soaks in water like a sponge. Water makes it swell unevenly, which causes bubble-like irregularities in the surface. Add enough water and the particle board will fall apart. So, in areas prone to water exposure, don’t use particle board.
Another common underlayment material is plywood, which has an advantage over particle board in structural strength and water resistance. One concern with plywood, as a walked-on surface, is that voids in the interior veneer layers may allow a depression in the flooring if weight were concentrated in one spot, such as a big ol’ girl wearing high heel shoes. I suppose that could happen, but it’s not likely. If this is a concern, marine-grade and underlayment-grade plywoods will avoid the voids.
Plywood used as underlayment for sheet vinyl flooring should also have a sanded, smooth surface on the topside. Avoid using materials with distinct raised grain patterns, which can affect the finish texture of the sheet vinyl.
Don’t overlook the importance of cleaning the subfloor before installing underlayment. Debris left on the subfloor can cause problems with the underlayment down the road. Whether your project is new construction or a remodel, the odds are pretty good some drywall joint compound (aka mud), construction adhesive or plaster is present on the subfloor from the wall finishing process. An uneven surface is not the only concern. These materials can break down over time, leaving a void between the underlayment and the subfloor. This void can allow noticeable movement, floor squeaks or cause fasteners to poke through.
We use a hand brush with stiff bristles around the entire perimeter to rake debris from under the drywall that could cause problems during the install. A thorough sweeping follows. Whoever does the sweeping should watch for nail and screw heads sticking up, as well as holes, large cracks, dry rot and other issues that may warrant subfloor repairs.
Some subfloor materials will soak in water and swell along the edges. Watch for this if your project experienced a lot of rain during the framing stage. The swelling results in ridges where the subfloor sheets come together. These ridges can create noticeable humps and bumps in the underlayment. They can also create voids between the underlayment and the subfloor, which can develop movement, floor squeaks and nail pops later.
We usually handle ridges in the subfloor by setting nail heads with a large punch and grinding, power planing or sanding the ridges closer to flat. A hardwood floor sander works great for this task.