Floor underlayment is a thin layer of material that is installed between the subfloor and a finished floor. Underlayment has several advantages including cushioning, moisture protection, noise reduction, insulation, and surface correction. This article explores these topics as well as the best floor underlayment for a variety of example projects.
The following topics are covered in this floor underlayment buyers guide.
- Purpose of Underlayment and Why It Is Important
- Floor Underlayment Side by Side Comparison Chart
- Best Foam Underlayment
- Best Felt Underlayment
- Best Underlayment for Tile Floors
- Floor Underlayment FAQ
- Considerations When Purchasing Floor Underlayment
- Types of Floor Underlayment
- Installing Floor Underlayment
- Tools Needed to Install Floor Underlayment
- Measures and Ratings Used When Comparing Floor Underlayment
Purpose of Underlayment and Why It Is Important
The key reasons to add underlayment under your flooring include the following.
- Cushioning. Underlayment adds a layer of cushion between the subfloor and finished floor which makes your floor more comfortable to walk and stand on.
- Moisture protection. Underlayment provides a barrier between your finished flooring and subfloor to protect your subfloor in the event water comes in contact with your finished floor. This is common in bathrooms, kitchens, and mudrooms where splashes and spills are common. In basements and other areas below grade, it can protect your flooring from moisture seeping up through the concrete which could damage your finished floor. In both cases, underlayment can help protect against moisture, mildew and mold.
- Noise reduction. Underlayment provides a layer of soundproofing similar to insulation between walls. It can decrease the sound transmission on second level floors from foot traffic and conversation between rooms. This is especially helpful in apartments, multifamily homes, or 2+ story single family homes.
- Surface correction. Subfloors are often uneven. Underlayment can smooth out imperfections in your subfloor and help ensure the final, finished floor lays flush against the subfloor.
- Insulation. Floor underlayment can provide an extra layer insulation, keeping your floors cool in the summer and warm in the winter.
Floor Underlayment Side by Side Comparison Chart
The table below contains our favorite floor underlayment by material type.
|Product||Price||Flooring Type||Material Type|
|ROBERTS “Serenity Foam” Underlayment||Check Price on Amazon||
|ROBERTS Super Felt® Underlayment||Check Price on Amazon||
|Schluter DITRA Underlayment||Check Price on Amazon||Tile||Polyethylene|
Note: since prices can change day-to-day, direct links are provided to check current pricing.
Best Foam Underlayment
Our favorite foam underlayment for projects on a budget is ROBERTS Serenity Foam Underlayment (Model 70-010). It is a competitive option to the big box stores. This underlayment is manufactured with open cell polyethylene foam. It measures 3/32” thick.
As a basic foam underlayment, it is best used with laminate and wood floors above grade. It can also be used on concrete floors if used in conjunction with a moisture barrier.
It does not have an adhesive backing. You will need tape to seal the seams or apply an adhesive to bond the material to the floor.
Best Felt Underlayment
Our favorite felt underlayment is the ROBERTS Super Felt® Underlayment. It is suitable for use below grade, at grade, and above grade. The underlayment works great on laminate, engineered wood, and concrete floors.
This underlayment has a plastic film layer that serves as a moisture barrier which helps prevent moisture from seeping up and damaging your finished flooring. It can also be installed on a radiant heat floor.
The ROBERTS Super Felt® Underlayment has good noise reduction properties. The underlayment has a “Sound Transmission Lost Test” (STC) rating of 66. Its “Impact Sound Transmission Test” (IIC) is rated at 67. The underlayment comes with an adhesive strip that easily allows you to link each run. This makes seaming the underlayment together quick and effective.
Best Underlayment for Tile Floors
The best underlayment for tile floors is Schluter DITRA. The DITRA product is a polyethylene underlayment with a grid structure top in the style of an egg crate and a fleece backing. It is designed specifically for ceramic and stone tile installations.
DITRA is an uncoupling membrane that provides a separation layer between the tile and the subfloor. This separation layer prevents tile and grout from cracking because it allows movement as materials expand and contract from temperature changes, humidity, and other environmental factors.
Schluter DITRA is a great alternative to cement board which is usually used with tile floor installations. It costs less than cement board, is lighter weight, and can carry the load of heavy tile.
DITRA is waterproof which makes it ideal for areas where tile is typically installed such as bathrooms where water damage is a risk. When installed correctly, this product will help protect your OSB or plywood subfloor from splashes and accidental overflows.
The egg crate-style top serves as a matting for the tile to lay on top of. This allows excess water that seeps through the tile flooring to have a place to drain without damaging the finished floor.
The fleece backing ensures a tight bond to the subfloor with a layer of Thin-set mortar. Thin-set is used to bond the underlayment to the subfloor and the tile to the underlayment.
The DITRA underlayment comes in two sizes. The standard size is 1/8” and the DITRA-XL size is 5/16”.
The DITRA-XL is suitable for subfloors installed on joists that are spaced 24” on center. The XL model allows a greater movement accommodation for natural stone tile and oversized tile. Since it is thicker, it can also be used to raise the tile, making it flush with flooring that sits higher (such as hardwood). This makes the transition between rooms look seamless.
Floor Underlayment FAQ
Q: How is underlayment attached to the subfloor?
A: It depends on the type of subfloor and the material the underlayment is made of. If the subfloor is concrete, an adhesive is required because you cannot staple into concrete. An adhesive is also required if the underlayment has a moisture or vapor barrier. Staples create holes and you do not want holes in a barrier meant to protect your subfloor from moisture. If you are applying the underlayment to a wood subfloor, without a moisture barrier, and the manufacturer allows staples for your particular product, then the underlayment can be stapled to the subfloor.
Q: What type of underlayment should be used for hardwood floors?
A: Felt underlayment is most commonly used with hardwood floor installations.
Q: What are the benefits of using floor underlayment?
A: Underlayment offers cushioning, moisture protection, noise reduction, surface correction, and insulation.
Q: Is underlayment necessary for all types of flooring?
A: Not for hard floors, but an underlayment is recommended because it’s the foundation of your floor installation. In most cases a padded underlayment is required for carpet.
Q: What types of floor underlayment are available?
A: The most common types of underlayment are foam, rubber, felt, and cork.
- Foam is the most popular and commonly used under laminate and floating wood floors.
- Rubber is often used in basements and other below grade areas where moisture is a concern.
- Felt is made of dense fiber materials. It provides a stable surface and has good insulating properties.
- Cork is an environmentally friendly option providing sound absorption and insulation. Cork is often used under hardwood floors.
Q: How much underlayment do I need for my project?
A: Purchase about 15% more than the square footage you are covering. For example, if your room is 15’ x 20’, you are covering 300 square feet. Plan on purchasing about 350 square feet of material. If each roll of underlayment is 100 square feet, you would need 4 rolls.
Q: Can I install underlayment over concrete?
A: Yes, but there are special considerations when installing underlayment over concrete.
- You must make sure the concrete is in good condition. If it is cracked or significantly uneven, it must be repaired before installing underlayment.
- The concrete must be clean and dry.
- Strongly consider installing underlayment that contains a vapor or moisture barrier, especially if the concrete is below grade. Moisture can seep through the concrete and damage your finished floor. A moisture barrier will help mitigate water damage.
Q: Can I install underlayment over an existing floor?
A: Generally, yes. However, make sure the floor you are installing over is in good, solid condition since it is serving as the foundation for your new floor. A major exception is hardwood floors. It is not recommended installing hardwood floors over an existing floor due to issues with expansion and contraction. If you choose to install over an existing floor, consider using an underlayment that is designed for that purpose.
Q: Is it necessary to use a moisture barrier with floor underlayment?
A: A moisture or vapor barrier is necessary when installing over concrete, installing a floor at grade or below grade, rooms subject to humidity or has historically been prone to moisture, and rooms such as kitchens, mudrooms and bathrooms where moisture can be reasonably expected.
Q: Are there considerations for underlayment in different climates?
A: In humid locations or areas prone to moisture, an underlayment that has a vapor barrier and suitable for expanding and contracting is required.
Q: Why is waterproof underlayment important?
A: Waterproof underlayment should be installed in the bathroom, kitchen, laundry room, mudroom, and any other areas that are prone to water. For example, if kids splash water out of a bathtub, a toilet overflows or leaks, washing machine overflows, pipes bust, or any other scenario when water comes in contact with the floor, a waterproof underlayment will save your subfloor from damage.
Q: What can be done to prevent tile from cracking?
A: To prevent tile from cracking it is imperative the tile is installed on a stiff, solid, and completely flat surface. Otherwise, the tile can shift and has a high risk of cracking over time. Tile is typically installed on cement board or an underlayment designed specifically for tile such as Schluter DITRA.
Considerations When Purchasing Floor Underlayment
When purchasing floor underlayment, there are a few key items to consider.
- Compatibility with your finished flooring. Whether you are installing luxury vinyl plank (LVP), laminate flooring, real hardwood floors, tile, or any other flooring type, it is important to make sure the underlayment is compatible. The flooring you are installing should outline the specifications for compatible underlayment. The warranty on your finished flooring could be voided if the manufacturer’s specifications are not followed.
- Thin, but dense underlayment. Density matters and denser is better. When choosing an underlayment, it is almost always best to purchase the most thin and dense material your budget allows.
- Durability. The underlayment needs to last as long as your finished floor. It will need to withstand constant compression from standing and walking on it. It also needs to withstand climate-related factors to your specific location such as temperature swings and humidity. It is also important for the underlayment to stay in place and not slide.
- Ease of installation. This is especially important for DIYers with limited experience installing flooring. A few examples of how manufacturers make underlayment easier to install include user-friendly designs such as fold out panels instead of a roll, pre-cut rolls, self-adhesive backing, guides for cutting, lightweight material, and detailed instructions.
- Certifications and Standards. The organizations that certify underlayment are the Flooring Industry Council for Sustainable Flooring (FICSF) and the Floor Covering Industry Foundation (FCIF). Comparing measures and certifications from these organizations can help ensure the underlayment has been tested and meets performance criteria. Industry standard measures include the following:
- Sound Transmission Class (STC)
- Impact Insulation Class (IIC)
- Sound Reduction Index (SRI)
- Sound Absorption Coefficient (SAC)
Types of Floor Underlayment
The different types of materials floor underlayment are made of include foam, cork, rubber, felt, and cement board.
Each of the material types are described below in detail. However, in cases where the floor manufacturer requires a specific type of material for the underlayment, follow the manufacturer’s directions.
Foam Floor Underlayment
Foam is the most popular type of underlayment as it is relatively inexpensive, lightweight, easy to install, provides cushioning, and in some cases insulation.
It is a basic, but versatile underlayment that can be used under vinyl, laminate, and wood floors. It is offered as a thicker material for carpet to provide extra cushion.
Foam underlayment is typically manufactured from two types of material – polyethylene and polyurethane. Polyethylene is lightweight, flexible, and usually cheaper than polyurethane. Polyurethane is a higher quality material which does a better job at dampening sounds, providing a layer of insulation, and is overall more durable than underlayment made of polyethylene.
Rubber Floor Underlayment
Rubber is the most durable type of underlayment due to its strength and flexibility. This makes it a great option for areas with high foot traffic.
Rubber is one of the best materials for areas where moisture is a concern, such as basements, bathrooms, or mudrooms.
Rubber underlayment is a viable option for laminate, carpet, or real wood floors. However, it is not recommended for use under vinyl. Rubber contains oils that can interfere with the adhesive on vinyl floors and can cause staining. Foam or cork underlayment is the better option for vinyl floors.
Cork Floor Underlayment
Cork underlayment is a great option for sound absorption and noise reduction. It is commonly used in apartments, multi-family housing, and other structures where sound transmission is a concern.
Cork is the most environmentally friendly material of the different types of underlayment.
Cork should not be used in damp environments unless it is specifically designed for moisture prone areas or coupled with a vapor barrier.
Felt Floor Underlayment
Felt underlayment is comparable to foam, but denser. It great for noise reduction, cushioning, and providing an extra layer of insulation.
Felt can be used on all floor types. It is not suitable for damp areas such as bathrooms, laundry rooms, and basements.
Felt underlayment is made by pressing and condensing fibers together. In many cases it is made of recycled materials which makes it an eco-friendly option.
Cement Board Underlayment
Cement board underlayment is made from cement and fibers. It is very strong and sturdy as it is often reinforced with wire or mesh. Cement board is typically used with tile installations since tile requires a flat and sturdy underlayment to prevent them from shifting and cracking.
Cement board is water resistant which is ideal for areas where tile is typically installed such as bathrooms, kitchens, and laundry rooms.
Installing Floor Underlayment
Before getting started with installing floor underlayment, measure the space you are covering to determine how much material you will need. Be sure to purchase enough to allow about three inches of overlap between runs.
The following are high level steps that will suffice for most installations. As always, follow the manufacturer’s instructions when specific instructions are provided.
Step 1 – Determine the Type of Underlayment Required
The type of floor you are installing (i.e. vinyl, laminate, wood, tile, etc.) determines the type of underlayment material required.
In wet areas such as a bathroom around bathtubs and showers, be sure to use underlayment that is waterproof and specifically designed for damp or wet areas.
There are special considerations on concrete floors or below grade areas such as a basement. Vapor barriers are often installed to prevent moisture from rising and damaging the finished floor.
Step 2 – Prepare the Subfloor
Remove the old flooring and dispose of it. After the old flooring has been removed, you will need to prepare your subfloor by repairing any unevenness, cracks, or other minor imperfections such as raised nails.
It’s important that your subfloor lays as flat as possible. Underlayment can correct minor unevenness, but if it is significantly out of plumb the floor will need to be repaired before proceeding.
If the floor is below grade (i.e. in a basement) small cracks in the subfloor can allow moisture to seep through and cause damage to the underlayment and finished floor. Any cracks in the cement will need to be repaired before moving forward with the installation.
Finally, you will need a clean surface to work on. Be sure to sweep up any dust and debris before installing the underlayment.
Step 3 – Lay the Underlayment
After the subfloor has been prepped, the next step is to trim and lay the underlayment. In most cases, the underlayment comes in a roll.
Begin on one side of the room and start unrolling the underlayment. Leave about three inches of extra material to overlap the next run.
Be sure to trim around walls, pipes, doorways, air vents, and any other permanent fixtures in the room. A utility knife can be used to trim.
Underlayment is attached to the subfloor by staples or adhesive. It’s best to do a “dry install” first to make sure you have made the correct cuts before permanently bonding the underlayment to the floor.
Adhesive should be used in lieu of staples for installations that contain a moisture or vapor barrier. Puncturing a vapor barrier with staples would allow liquid to leak through the barrier. Installations over concrete also require an adhesive.
Foam or felt underlayment installations can be stapled to a wood subfloor as long as there is no moisture barrier and it is allowed per the manufacturer’s instructions.
As always, be sure to check the manufacturer’s instructions in case there are steps that need to be taken for your specific product.
Tools Needed to Install Floor Underlayment
The following tools are required to install floor underlayment.
- Stapler or adhesive depending on the manufacturer’s recommendation. In some cases, the underlayment will be preinstalled with an adhesive backing. Adhesive is required for concrete floors.
- Utility knife. A utility knife is needed to cut and trim the underlayment.
- Straight edge. Required to make sure you are making even cuts.
- Tape measure. Needed to measure the area the underlayment will be installed and determine how much material is required.
- Hammer. A hammer is needed to drive down any staples that didn’t set evenly on the subfloor. It is also used when preparing the subfloor to hammer down any standing nails.
- Roller. If adhesive is used, a roller is helpful to apply pressure to the underlayment and help it bond to the subfloor.
- Knee pads. Much of the installation process will be spent on your knees.
- Gloves and safety glasses. A general recommendation for overall safety.
Measures and Ratings Used When Comparing Floor Underlayment
When purchasing floor underlayment, there are a few measures or ratings that can be used for comparison.
- “Sound Transmission Class” (STC) test. The STC test is a measure of a building material’s effectiveness in blocking sound. The STC test is represented by a number that measures the decibels (dB) of sound transmission through the material. The higher the number of decibels, the better the material is at blocking sound. It is a common measure used in the construction industry to measure sound insulation properties of building materials. Examples of noises that apply in a residential setting include sounds from a TV, conversation, and music.
- “Impact Insulation Class” (IIC) test. The IIC test measures the effectiveness of a floor or ceiling at blocking noise. In residential settings, this test commonly applies to single family homes with two or more stories, apartment buildings, multi-family homes, or any other structure where blocking noise from foot traffic or dropped objects is a concern. A higher IIC rating suggests the material is more effective at blocking sound.
- “Sound Reduction Index” (SRI). The SRI is calculated by adding the STC and IIC test, then subtracting a correction factor. In other words, the SRI takes into account both airborne noise (TV and conversation) and impact noise (footsteps from the floor above).
- “Sound Absorption Coefficient” (SAC). The SAC is a measure of a materials ability to absorb sound. It is measured in a range from 0 to 1, where a higher coefficient reflects grater sound absorption properties.
- Density. In general, a denser underlayment represents a higher quality material. Factors include:
- Stability – denser underlayment is unlikely to shift and settle over a long period of time. This is important to maintain a level and stable surface for the finished flooring.
- Durability – for areas with a higher level of foot traffic, a denser underlayment will withstand wear and tear.
- Performance – in general, denser underlayment will perform at a higher level in terms of sound reduction, moisture barrier, and insulation.
- Thickness – thicker material can play a role in air and sound insulation, but is not a substitute for density, sound transmission class, and impact insulation class. In other words, just because an underlayment is thicker does not necessarily mean it insulates or blocks sound more efficiently. The materials thickness can have a positive impact on cushioning the final floor. It can also correct unevenness on the subfloor by making a flatter surface to lay the final floor. Verify it is not too thick for the specific floor you are laying as it could cause hard floors to split if there is too much cushion.