Complete Guide: Underlayment for Vinyl Sheet Flooring

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.

Particle Board

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.

We use a stiff-bristle hand brush to get debris out from under the drywall

Clean Sweep

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.

Typical constuction debris on the subfloor includes drywall compound, bits of insulation, expanding foam and drill debris from plumbing and electrical operations.

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.


Like many of our home improvement projects, proper preparation is important to the success of an underlayment install.

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.

We load our sheets of underlayment material on sawhorses for easy layout and cutting.

Vapor Barriers

Moisture content in the subfloor should be low before installing underlayment. In some cases a vapor barrier should be used between the subfloor and the underlayment, particularly for first-floor applications when using particle board underlayment over a subfloor other than exterior-grade plywood.

If a vapor barrier is not required by code, you need to decide if the subfloor provides protection against moisture. If it’s car decking (tongue-and-groove dimensional lumber) with gaps and knot holes, a vapor barrier is a good idea. Vapor barriers are usually polyethylene sheets (4 mil or thicker) or asphalt-layered kraft paper.

Determining the floor break in kitchen areas often requires a careful examination of the cabinet plan.

Floor Breaks

OK, your subfloor is ready, the material’s been selected and protected with the proper vapor barrier and now you’re ready to start running that new circular saw, right? Hold on there, Sawyer—you gotta figure out your floor breaks next.

We use a T-square to mark underlayment sheets for cutting. Look in the drywall tool area to find a good T-square for your underlayment install.

Floor breaks are where the vinyl meets the carpet (or whatever other flooring is adjacent to the flooring you are preparing to install on your underlayment). The edge of your underlayment is the place where the vinyl and the carpet meet. If, for example, you are installing vinyl in a bathroom, you will want to make the floor break under the door going into the bathroom.

Set the depth of your circular saw to about 1/4″ beyond the material thickness.

If the door swings into the bathroom, then the floor break will extend into the door opening about 1 inch from the face of the drywall inside the bathroom. If the door swings out of the bathroom (such as into an adjacent walk-in closet), then you’ll extend the underlayment into the door opening until it is about an inch toward the bathroom from the inside face of the wall of the adjacent room. In other words, figure out where the door is and place the edge of the underlayment right under the center of the door panel.

We use Porter Cable’s new 18-volt Lithium 6-1/2″ circular saw for our underlayment project.

There are a few exceptions I make to this floor-break-under-the-door rule. One is in the case of bifold or bypass doors where there is vinyl on one side and carpet on the other. Because bifold doors tend to be a bit higher off the floor and bypass doors do not line up with each other, it’s often preferable to have the floor break on the inside of the closet area where it is unlikely to be seen when the doors are closed. Just imagine the flooring behind the doors peeking out into the living area and you’ll make the right call.


After notching the sheet so the floor break extends into the door opening, you can then layout other cuts as measured inside the walls.

When the floor break is in an open area such as a transition between a nook area and the living room, you’ll have to decide how to make that happen so it looks best. If there is an archway or half wall on either side, it’s generally preferable to split the flooring types in the middle of the dividing wall or arch or cased opening where there is no door.


The preferred method for carrying a sheet of underlayment is one hand under and one over. This gives you good control to negotiate hallways and door openings.

In the case of a kitchen or bar area, you need to know the cabinet layout so you can make the floor break at the edge of the outside cabinet box. If there are cabinets on both sides of the opening, plan the floor break to go in a straight line between the outside corners of each of the outside toe kicks.

Be careful not to damage walls and tubs as you maneuver sheets into place.

Sheet Orientation

Once you’ve decided on the floor breaks, you can measure, cut and install your underlayment. In most cases I begin with the biggest piece I can fit in a room (usually a 4-by-8-foot sheet) right in the door opening so you avoid putting seams in the areas that will be walked on most.

Keep the piece on plane with the down edge parallel to the wall as you ease the piece into position.

Whenever practical, run the long direction of the underlayment sheets in the opposite direction of the subfloor material so they cross each other. This adds to the floor’s structural strength. Avoid placing sheets of underlayment in such a way that the seams of the underlayment correspond or line up with the joints in the subfloor.

Check the piece for parallel to the walls before tacking it into place.

If the floor break takes place in an area other than under a door, I prefer to lay the first sheets along the floor break edge and work back into the vinyl area of the room. This allows me to cut and fit the smaller pieces against the walls and under the cabinet areas where the tolerances are less demanding. Also, if you start with a nice straight factory edge along a carefully established floor break it will greatly improve the transition between flooring types.

After establishing the floor break with the outside piece, add material to the inside of the room to complete the install.


Whenever possible, plan your cuts so the factory edges of the underlayment come together, and place the saw-cut edges on the perimeters against the walls. Give yourself 1/8 to 1/4 inch of room along the walls. In fact, you can leave gaps the thickness of the base board. It’s better to have a little wiggle room than to scratch up the walls.

Fastener spacing should be approximately 3″ on the outside perimeter of each piece.


Leave a small gap between the underlayment and showers or tubs to avoid squeaks.

As you install the pieces, move them away from the wall and tighten the joints out “in the field.” When the pieces fit and the joints are tight, tack them in place with a ring-shank nail or with the staple gun.

Bathroom underlayment.


Floor breaks at door openings should line up with the center of the door itself.

Leave a little room (1/16 inch or so) along fiberglass showers and tubs. Even a little floor flex can cause a squeak where the underlayment rubs these fixtures. If you are installing vinyl flooring in a large area where light from a patio door shines across the surface, it’s a good idea to use carpenter’s glue at the seams between pieces to ensure that they stay well connected to each other as well as to the subfloor.

Fastener spacing should be approximately 3 inches on the outside perimeter of each piece.

Nailing patterns should be 3 inches on the perimeters and 6 inches in the field. Before nailing off the pieces in the field, drive a few fasteners with plenty of weight near the nailing spot to make sure the underlayment is against the subfloor.

This utility room floor break is well behind where the bifold doors will be, so the flooring cannot be seen when the doors are closed.

Proper preparation of the subfloor, careful consideration for floor breaks, tight seams and thorough fastening will ensure that your underlayment will provide a good platform for your sheet vinyl flooring for years to come.


Big Cuts/Small Saw

You can cut a piece wider than the capacity of your small table saw by marking the desired width on the piece and measuring to the mark from the opposite edge. Set the saw to cut off the proper amount by measuring to the outside of the saw blade. This approach allows you to use the fence on the table saw for a nice straight cut even though the finished piece (on the other side) is wider than the saw’s capacity.


Cordless Advantage

One of the biggest advantages to cordless technology is being able to easily take the cutting tool to the room where a tricky piece needs to be cut for installation. Some underlayment pieces are like jigsaw puzzle pieces, which makes a cordless jigsaw an ideal tool to make the piece fit the puzzle.

Starting with a basic rectangular piece, you can mark your measurements directly onto the piece as you take them. This avoids the need to write down measurements or to draw a diagram. You can cut out openings*, make adjustments, and test fit your piece without ever leaving the room.

*Tim, you really should use a sawhorse for this operation.

Out of Bounds

When the center of a toilet drain falls outside of the sheet you are working on, you can extend the layout onto the sheet underneath and anchor your pivot nail there.

With the pivot nail in the sheet underneath, you can use your 3-1/2-inch radius jig to draw an arc for the toilet drain cutout.
Cut out the toilet drain opening with a jigsaw.

What About Tile Floor Underlayments?

Some tiled floors last for hundreds of years and others start to show cracks after only a few months. Why? The reason can be best summed up in one word—uncoupling.

An uncoupling layer allows the tiled surface to move independently of, or be ‘uncoupled’ from, the subfloor. In recent years many installers have been inappropriately working to create a more secure bond by adhering tiles directly to the subfloor. The problem with this “direct bond” approach is that the subfloor expands and contracts due to changes in moisture and temperature, which exerts incredible stresses on the tile layer. The tiles and grout don’t expand and contract at the same rate as the subfloor, so tiles and grout are both vulnerable to cracking and buckling.

So, what about those 100-year old floors that still look great? “The theory is simple,” says Peter Nielsen, technical director for Schluter-Systems. “For centuries tiles were successfully installed on a layer of sand, which worked very effectively as an independent uncoupling layer between the structural base and the tile floors. In more recent times, a thick wire-reinforced mortar bed placed over a slip-sheet was used to achieve this same function. Although highly successful, these traditional methods have the limitations of being thick, heavy and challenging to install, and they are not at all suited to modern home construction.”


Schluter-DITRA is an uncoupling membrane engineered for modern construction techniques. DITRA is only 1/8-inch thick, weighs only two ounces per square foot and is easy to install. The matting allows construction materials beneath the tile to breathe, but it is impervious to water so floors and ceilings will not be damaged by spills and leaks. The system is designed for use on all of the most commonly used subfloor materials—plywood, OSB, concrete and gypsum-based screed.

The uncoupling membrane is adhered to the surface being tiled using a layer of thinset adhesive applied with a 1/4-inch V-notch trowel. The tile is then adhered to the uncoupling membrane using another layer of thinset. Also available is DITRA-XL, which is 5/16-inch thick to allow for even transitions between typical ceramic tile and 3/4-inch thick hardwood flooring. For more information, visit


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