Most flooring requires underlayment to cover imperfections in the subfloor, reduce sound and provide other benefits specific to each type of floor covering. It may not be sexy, but it is essential! Choosing the right underlay product is important to getting a completed project you’ll really be happy with, but it is one that many homeowners don’t give much thought to.
This guide will help you achieve the results you want whether you install the underlayment and flooring yourself or hire a contractor.
The Purpose of this Underlayment Guide
Our purpose here is to deliver a comprehensive guide to underlayment that will help you select the right type for your flooring or discuss your options with a flooring contractor.
This underlay buyers guide includes underlayment prices for each type, names of the best brands and an overview of underlayment installation.
What is Underlayment?
Underlay is the layer of material directly beneath your floor covering. If you were to tear up the flooring in your home, you would likely find many layers. When you removed the floor covering, also called the finish floor, you’d expose the underlay. Remove that, and you would find a subfloor such as OSB (oriented strand board), plywood or concrete. A moisture and/or vapor barrier might be found among the layers too, especially in basement flooring, or the underlay might include a barrier in its construction.
Each finish flooring material requires an underlayment specifically designed to optimize its appearance, performance and durability. Depending on the flooring you are installing, the underlayment might be a hard material such as plywood or cement board or a soft material such as felt or carpet padding.
Flooring Types and the Right Underlayment for Each
Let’s get into the details here with a list of the most common types of underlay used in flooring today. We divide the list by the types of flooring, so you can zoom in on the products suited to your project.
Tile Flooring Underlayment
Tile floors remain a popular choice, especially for bathrooms, entryways and other places a water-resistant surface is desired. The impressive variety of tile styles, shapes and colors allows you to customize your design.
Tile underlayment must provide solid support, so the tile and grout won’t crack when walked on. However, it must also be somewhat flexible to absorb movement and any expansion or contraction that comes with changing temperature and humidity. Two materials meet these requirements exceptionally well.
CBU or Cement Board Underlayment
CBU consists of cement material and fibers made from wood or cellulose. The fibers reinforce the cement and also give it a certain amount of flexibility that allows for movement without cracking the cement. Cement board is manufactured in several sizes including 3’x5’ which is the most popular and 4’x8’. Typical thicknesses are 1/4″ and 1/2″. It is also called cement backer board.
- Top brands: US Gypsum, James Hardie, PermaBase
- CBU price: $0.75 to $1.10 per square foot.
- CBU installation: The board is typically nailed or screwed to the subfloor, though it can be glued as well. It can be cut with a utility knife or saw. Seams should be filled with thin-set mortar to create a more level surface for the tile.
DITRA Uncoupling Membrane
This premium underlay is manufactured from polyethylene with a unique design. DITRA features a grid structure of square cavities, the base of each cavity being larger than the top. This allows tile mortar, which bonds to the tile, to anchor within the cavity when it hardens. Check out our in-depth guide to Schulter Ditra.
The DITRA membrane, which is 1/8” thick, prevents the mortar from bonding to the subfloor. Instead, a fleece backing is laminated to the underside of the DITRA, and the backing is adhered to the wood or concrete subfloor using thin-set mortar.
DITRA is an underlayment that allows for movement and expansion/contraction while preventing the transfer of stress that commonly cracks grout and tile. This polyethylene membrane is an excellent moisture and vapor barrier too, and it can be installed over wood or concrete including floors with radiant heat. DITRA and the thicker DITRA-XL come in rolls 3’ wide.
- Brand: Schluter DITRA and DITRA-XL
- DITRA price: $1.55 to $1.90 per square foot
- Schluter DITRA installation: Installation is easily accomplished by rolling out the material with the fleece side down and using a utility knife to make cuts for obstacles such as drains and posts. Then, the material is rolled up again, and the floor is covered with thin-set mortar using a notched trowel. The DITRA is rolled out over the mortar making sure the fleece and mortar are in contact over 100% of the surface. A screed trowel or concrete float is used to press the material’s fleece into the mortar and to remove air pockets working from the center toward the edges.
To Get Started
If you’ve got an older home with concrete subfloors, then it is likely that those subfloors are cracked, uneven or have low spots caused by settling. You can’t install flooring directly over them and expect the job to look good or last.
The solution to installing flooring over concrete that is in poor condition is self-leveling underlayment, a concrete product that mixes quite thin and pours easily. Like any liquid, its surface will become level. This forms an outstanding platform for additional underlayment such as carpet padding, DITRA or plywood.
An additional benefit of self-leveling underlay is that it works well with radiant floor heating systems. The tubing the heated water is circulated through is placed on top of the old concrete, and the self-leveling underlay is then poured over the tubing.
- Top brands: Bostik, Quickrete, Henry, LevelLite, DAP Ardex
- Self-leveling underlayment price: A 40lb to 50lb bag costs $30 to $36 and covers 40 to 50 square feet to 1”.
- Self-leveling underlayment installation: One inch is typically the maximum thickness this can be poured, and that’s plenty to cover radiant floor tubing. Low spots deeper than 1” will need to be filled with an initial layer of this material or with standard concrete before a self-leveling material is poured over it. The bag of underlayment will give complete instructions for mixing and pouring. You’ll need a 5-gallon pail, an electric drill and a mixing paddle. Typically, the pail is filled with water, and the mix is added slowly while the paddle blends it. Most materials need to be poured within about 10 minutes of when they’re mixed.
Laminate Flooring Underlayment
Laminate flooring is an attractive and durable alternative to hardwood flooring, and it typically costs less. If you purchase high-quality laminate flooring, it might already have underlayment included in its construction. This simplifies installation by eliminating a time-consuming step.
If your product doesn’t have underlay attached, you’ll need to select one of these products in order to cover minor imperfections in the subfloor and give the laminate greater stability.
Foam Laminate Underlayment
Foam is the most basic laminate flooring underlay. The foam is 3mm (1/8”) to 6mm (1/4”) thick and comes in rolls of various widths and lengths.
There are two types of foam underlayment – combination laminate underlay with an included moisture/vapor barrier and foam with no barrier. Choose a combination product when installing laminate flooring in the basement or any area, such as a bathroom, where high humidity is often produced.
Upgraded foam underlayment for laminate is material that includes rubber or fibers to provide greater durability. It also helps to reduce the amount of noise that passes through the floor from level to level.
- Top brands: QEP Roberts, MP Global, Courey Eco-Friendly, KronoSwiss, LVT
- Foam underlayment prices: Standard foam underlayment costs are $0.22 to $0.30 per square foot depending on the quality. Upgraded foam underlay ranges from $0.30 to $0.45 per square foot.
- Foam underlayment installation: Foam underlay is produced in rolls, and it is pretty easy to install for a DIY homeowner with basic skills. Simply roll out the material and use scissors or a utility knife to trim edges and around obstacles. The edges of all laminate flooring underlayment should be butted rather than overlapped.
Acoustical Laminate Underlayment
When you want to minimize the hollow sound caused by foot traffic, acoustical laminate flooring underlay is the right choice. Cork and felt varieties are available, and most have a moisture barrier included. They’re 3mm (1/8”) thick to 6mm (1/4″) and require only basic skills to install.
- Top brands: QEP Roberts (cork and felt), Eco-Cork (cork), AcoustiCORK (cork), WidgetCo (cork), Bildermann’s (felt), Blue Hawk (felt)
- Acoustical laminate underlayment prices: $0.50 to $0.75 per square foot for cork; $0.75 to $1.25 for felt.
- Acoustical underlayment installation: Felt laminate underlay is produced in rolls. It can be rolled out and trimmed with a knife or scissors. Cork is produced in rolls and sheets, and it can also be cut with scissors or a knife. The edges should be butted, not overlapped.
Hardwood Flooring Underlayment
For our discussion of underlayment, a wide range of flooring comes under the heading of hardwood. It includes domestic solid hardwood flooring such as oak, maple, hickory and ash, and exotic varieties like Brazilian cherrywood, koa, teak or sakura. Engineered flooring with a layer of solid hardwood on top and layers of composite material beneath is included. We’ll throw in cork and bamboo too, since the underlay options are the same as for hardwood.
The most common hardwood flooring underlayment is felt, typically manufactured in rolls. It is very dense, and most products are 3mm (1/8”) to 6mm (1/4″) thick. The felt offers decent resistance to moisture from below, but in very humid areas, a moisture barrier should be installed too.
- Top brands: QEP Roberts, Bellawood, Bildermann’s
- Felt underlayment prices: $0.75 to $1.25 depending on density and thickness.
- Felt underlayment installation: If you’ve got reasonably good skills, you won’t have trouble installing felt underlay. Roll it out and use a knife or scissors to trim edged and around obstacles. Ask your supplier about whether to glue down the felt. It will depend on the subfloor type and the finish floor you’ve selected.
Cork is also used beneath hardwood flooring, and you’ll find products with and without a moisture barrier included. Generally speaking, wood should be allowed to breath, and hence, no moisture barrier is needed.
However, in high-humidity locations, it’s safer to use a barrier. Remember, solid hardwood shouldn’t be installed in basements or wet locations.
- Top brands: Eco-Cork, AcoustiCORK, Manton, WidgetCo, QEP
- Cork underlayment prices: $0.50 to $0.75 per square foot; a hybrid cork/rubber underlayment is a premium product costing $1.15 to $1.50 per square foot.
- Cork underlayment installation: This is a pliable material that can be easily trimmed to accommodate drains, doorways and other obstacles.
Rubber underlayment is a third choice for use with hardwood floors. In addition to excellent moisture resistance, the rubber does a good job reducing noise. It does not need to be glued down, and that saves time and hassle during installation and removal in the future.
Available from 2mm (5/64”) to 9mm (3/8”), rubber underlayment offers a moisture barrier and better sound-reducing qualities than foam or cork. Rubber also offers superior insulation. It is easy to work with, but it costs more than other underlayment options.
- Top brands: Sound Terminator, RB Silent Tread, Absorba Sound, Rubber Flooring
- Rubber underlayment price: $1.15 to $1.50 per square foot.
- Rubber underlayment installation: This material is produced in rolls and is easily cut to size and trimmed for fit. No gluing is required. Seams should be butted rather than overlapped.
To Get Started
Foam Underlay for Engineered Hardwood
Foam is a versatile underlay that provides good sound absorption, resists mold and can be recycled. Upgraded foam includes rubber or fibers of other material to increase density, moisture resistance and durability. You’ve got your option of foam with a moisture barrier included, often called combination foam, or foam without a barrier. The combination foam is the right choice where high-humidity conditions exist in the room or in space beneath the room where hardwood floors are installed. This underlay is similar to the foam underlay for laminate.
- Top brands: QEP Roberts, LVT, MP Global, Courey Eco-Friendly, KronoSwiss
- Foam underlayment prices: Standard foam underlayment costs are $0.22 to $0.30 per square foot. Upgraded foam underlay ranges from $0.30 to $0.45 per square foot.
- Foam underlayment installation: Foam underlay is available in rolls and will be easy to install if you have basic experience using hand tools. Roll out the material and use scissors or a utility knife to trim edges and around obstacles. The edges should be butted, not overlapped.
The primary type of carpet underlay is foam or rubber carpet padding, especially when the subfloor of wood or concrete is in good condition. Today’s padding options are larger than ever. Popular types include:
- Rebond padding made from pieces of high-density foam
- Standard urethane foam that is affordable but not suited to high-traffic locations
- Frothed foam that is denser urethane product for use where foot traffic is heavy
- Memory foam that is both comfortable and resilient
- Slab rubber is consistently dense and it wears very well, though it costs more than most foam pads
- Waffle rubber is more affordable than slab rubber padding, but it doesn’t offer the durability or comfort
Your carpet retailer will be able to suggest the proper carpet padding based on what the subfloor is made of and the carpet you’ll be installing. Perhaps it’s worth noting that the Carpet Cushion Council recommends padding at least 1/2″ thick for cut pile carpet, less for Berber style carpeting. Most carpet padding includes a moisture barrier.
- Top brands: ScotchGard, Step Ahead, Memory Foam, Traffic Master
- Carpet padding price: $0.55 to $1.10 per square foot depending on the thickness and quality
- Carpet padding Installation: The padding is easy to cut and trim around obstacles with scissors or a carpet knife. Seams are butted, and the material is installed with a staple gun and one staple every two to three square foot.
See our carpet buyers guide for more carpet buying and installation info.
The preferred underlayment for sheet vinyl flooring is 1/4″ plywood. Some installers will lay vinyl over existing OSB or plywood subflooring if it is in excellent condition. Plywood is available in 4’x8’ and 4’x4’ sheets.
- Top brands: All home improvement stores sell this material in open stock, and it usually doesn’t have a brand name associated with it
- Plywood underlay price: $0.40 to $0.55 per square foot for standard material and about $1 per square foot for premium material.
- Plywood underlay installation: For larger areas, use 4’x8’ sheets and for smaller areas such as bathrooms use 4’x4’ sheets. Remove toilets, pedestal sinks and similar fixtures before installation. Use a handsaw to cut pieces to size and to trim around drains and other obstacles. Seams in large areas should be staggered. Use 1 1/8” underlayment nails to secure the plywood to a wood subfloor and plywood adhesive to secure it to concrete. Fill the seams with self-leveling compound using a 6” trowel.
The Quality of the Installation is Crucial
If you’re planning a DIY project, take time to learn all you can about installation before you start. For your flooring to look as good as possible and perform as it should, it must be properly installed. When hiring a professional to install your flooring, it makes sense to get multiple estimates from local flooring contractors. Learn about their experience and check their references. This is the best way to find a quality flooring installer at a competitive price.
Q: Do you need underlayment for vinyl plank flooring
A: That’s a firm maybe! See our dedicated vinyl plank flooring underlayment post for the full story.
Q: How thick should underlayment be for vinyl flooring
A: A thin foam underlayment of no more than 3mm is sufficient and this type of underlayment often comes pre-attached to high quality vinyl plank floors.
Q: Do I need underlayment for laminate flooring?
A: Yes, but be aware that some laminate flooring comes with underlayment pre-attached so for these products it is not necessary to purchase and install further underlayment.
Q: What does underlay mean?
A: To underlay something is to support or raise something from underneath, for our purposes that means your flooring.