How to Select the Right Carpet Pad

Out of sight, out of mind, the saying goes. Maybe that's why the choice of a carpet pad -- aka underlay or cushion -- is often overlooked. Yet the right pad can make or break a carpet purchase because it plays a critical role in your carpet's performance and appearance.

Your carpet pad is a sheet of spongy material that goes underneath your carpet. It's cut slightly smaller than the carpet itself so it will fit inside the tack strip that keeps the carpet in place. Installers either staple or glue the pad to the subfloor, joining sections of padding with a specialized tape.

The main purpose of a carpet pad is to protect your carpet. The pad keeps the underside of your carpet from wearing against the bare floor. It also absorbs the impact from footsteps and furniture, lessening the stress on the carpet. In one study, carpets without cushioning lose, on average, 19 percent of their pile height from wear compared to a five to 10 percent loss for the same carpet with a separate pad [source: Carpet Cushion Council Benefits].

The carpet pad serves a variety of additional purposes:

It creates a softer "walk" or feel to the carpet. Many homeowners think this is the whole point of a pad, but it's not. In fact, the best pad for a particular carpet may provide less foot comfort than an inferior one.
A pad makes cleaning your carpet more efficient. When you have padding, your vacuum cleaner can raise the carpet slightly and remove more dirt, which helps reduce allergic reactions.
It provides thermal insulation. A pad stops the drafts that can seep through some porous carpeting. Padding has higher R-value -- which measures a material's ability to keep heat from passing through it -- than carpet, keeping the room warmer.
Carpet padding dampens sound. This is especially important for upstairs rooms, but even in a basement, a pad reduces sound more than a carpet alone.

Installing the wrong pad can sometimes void your carpet's warranty, so always look at the carpet manufacturer's recommendations. And think twice about the free pad offered by carpet retailers: Some retailers order padding by the truckload and push only one kind [source: Long's Carpet]. Decide on the pad you want and ask the store to order it if they don't have it in stock. If you're replacing carpet, don't be tempted to save by using the existing pad. It almost always needs to be replaced.

Before choosing your carpet pad, you should look at where you'll use it. Think about what kind of activities or traffic the room sees, and choose a pad that can take a beating if you think you'll be rough on it. If you stand a lot or have kids who will play there, consider thicker padding for increased comfort. Does someone in your home use a wheelchair? They don't roll well on soft padding, so take that into account, too. Regardless of everything else, when choosing your carpet pad, it all comes down to your particular needs, so don't let a salesperson who's more interested in installing the most expensive product sway you.

Read on to learn about a pad that uses air to cushion your carpet.

Carpet Pad: Waffle Rubber

Waffle rubber was once a common form of carpet padding, but it's not as popular now. These pads are made from spongy rubber material that's molded to create a waffle-like texture with hills and valleys. The carpet sits on top of the raised areas, letting the carpet rest partly on air. This cushion of air makes your carpet feel softer, but waffle rubber is sometimes too soft for modern carpets. It doesn't provide enough support and lets the carpet's backing wear and crack as it moves.

Despite its disadvantages, waffle rubber makes adequate padding if it has the proper density and thickness. Best of all, it's usually inexpensive and widely available. This type of padding also gives carpet the soft, cushiony feel that some homeowners prefer.

Regardless of any other traits, density -- or how much weight it has for a given thickness -- is the key to a carpet pad's usefulness. If your padding isn't dense enough, it won't adequately protect your carpet -- if the pad can be completely compressed, your carpet absorbs wear with each impact. In fact, a carpet pad's density is rated according to the force needed to compress it in this way.

The U.S. Department of Housing and Urban Development (HUD) has minimum standards for the various carpet pads, depending on the amount of traffic they are likely to endure. For light or moderate traffic, such as in a living room or bedroom, HUD recommends that waffle rubber be at least 0.285 inch (7.2 millimeters) thick and weigh 14 pounds per cubic foot (224.3 kilograms per cubic meter). For heavy traffic areas, like corridors or commercial lobbies, the recommendation is 0.33 inch (8.4 millimeters) and 16 pounds per cubic foot (256.3 kilograms per cubic meter) [source: CarpetInspector.com].

If you decide to buy waffle rubber padding, one thing to watch out for is the binding. Clay binders were once the norm for waffle rubber, but they have a tendency to disintegrate with normal wear. Be sure your carpet pad doesn't have clay binding, and always ask about the longevity of a waffle rubber pad before you choose to buy one [source: The Carpet Guru].

Maybe waffle rubber isn't for you, so read on to learn about foam rubber pads.

Do You Need a Moisture Barrier?

Does it make sense to install a separate moisture barrier between the carpet and the pad below? Many people think such a barrier will keep spills or pet accidents from reaching the pad, where they soak in and are harder to remove. Some carpet experts feel that these barriers aren't generally needed because many carpets include their own moisture barrier. Some pads, like Stainmaster Carpet Cushion, also have built-in, breathable moisture barriers [source: International Standards and Training Alliance].

Carpet Pad: Urethane Foam

Urethane foam is the material commonly known as foam rubber, which is produced by blowing gas into a heated, liquid chemical mixture. When it dries, the foam rubber is porous and spongy, and the gas trapped within the urethane foam gives it great insulative properties. This same material is used as cushioning for furniture, mattresses and car seats.

Manufacturers use two types of urethane foam in carpet pads: prime foam and frothed foam. The padding known as prime foam comes in different thicknesses and densities, and it's made from large pieces of foam sliced into sheets. While this type of foam rubber padding makes your carpet soft and comfy, it's not recommended for high traffic areas like stairways or halls. Foam rubber's cushioning comes from its air pockets, but as with waffle rubber, the air doesn't always provide enough support to limit carpet movement and protect your carpet from wear.

The HUD standard for prime foam, when used in light or moderate traffic areas is 0.375 inch (9.525 millimeters) thick and 2.2 pounds per cubic foot (35.2 kilograms per cubic meter). HUD does not recommend it for heavy traffic areas [source: CarpetInspector.com].

Some carpets have built-in pads made from frothed urethane foam. This material is similar to prime foam, but instead of having gas blown into the chemical mixture, it's mechanically frothed while liquid. The result is a denser, firmer type of foam that can be attached directly to the carpet. Carpets with built-in padding don't need a separate pad, but the attached foam is usually too thin to stand up in high traffic areas.

In recent years, manufacturers have extended the use of frothed foam to separate padding. They apply the foam to a nonwoven fabric to make the pad. Frothed foam pads are among the best on the market because they are extremely durable and provide excellent support. Unlike other foam pads, they contain no volatile organic compounds (VOCs), so off-gassing after installation is not a problem. They can be used with all carpets, and they resist indentation from furniture, which decreases carpet wear.

The HUD standards for frothed foam pads are a minimum of 0.25 inch (6.35 millimeters) and 10 pounds per cubic foot (160.2 kilograms per cubic meter) for light and moderate traffic. The same thickness, but 12 pounds per cubic foot (192.2 kilograms per cubic meter) is recommended for heavy traffic areas.

Keep reading to find out about the most common carpet pad.

Carpet Pad: Bonded Urethane

Bonded urethane foam, also known as rebond, is the most common type of carpet pad material. About 80 percent of pads sold are made of bonded foam, which is constructed of foam scraps left over from the manufacture of furniture, mattresses and automobile components [source: Carpet Information]. It may also come from scrap generated by the foam-making process and can include recycled, post-consumer foam.

The foam scraps are chipped into small pieces and then fused using either adhesive or a heat process. The foam is then bonded to fabric, net or plastic film to give the pad more strength and to make it easier to handle. Bonded urethane carpet pads use a great deal of foam that would otherwise go to waste, so the price tends to be low. Of course, prices will fluctuate with scrap foam's market value.

A bonded pad is versatile and can be a good choice for most situations, as long as you avoid padding that's too thick. The Carpet and Rug Institute advises that no pad should be more than seven-sixteenths of an inch [source: Carpet and Rug Institute]. In part, this is because a thick pad allows too much up-and-down movement of the carpet, wearing the backing as it flexes. Also, a pad that's too thick can allow the carpet to pull away from the tack strip that holds it flush with the wall.

The minimum HUD standards for bonded urethane foam are 0.375 inch (9.525 millimeters) and 5 pounds per cubic foot (about 80 kilograms per cubic meter) for light or moderate traffic areas, and the same thickness requires 6.5-pounds-per-cubic-foot (104-kilograms-per-cubic-meter) foam for heavy traffic [source: CarpetInspector.com]. Many professionals and carpet manufacturers recommend even denser foam, especially for hallways. Foam in weights from 7.5 to 8 pounds per cubic foot (120 to 128.1 kilograms per cubic meter) will hold up better and help protect your carpet.

Remember that bonded foam will not hold up as long as premium pads like frothed foam or rubber. Some carpet retailers sell inferior bonded urethane foam that may lack the proper density for your specific application. Another concern with bonded foam is the out-gassing of butylated hydroxytoluene (BHT). This chemical was once added to urethane foam to reduce its flammability. It can yellow carpet, especially light-colored olefin. Bonded foams are less likely to contain BHT today, but make sure the seller guarantees it will not harm your carpet [source: Carpet Buyers Handbook].

On the next page you'll read about the pad that gives your carpet maximum support.

Going Green with Carpet Pads

Bonded urethane carpet padding is the result of a major recycling effort in the industry. Like carpets themselves, carpet pads take up room in landfills and often use nonrenewable resources. Homeowners concerned about the environment can find green alternatives. In addition to bonded, they can choose natural rubber and fiber pads made from sustainable materials. In Maine, a program has been set up to reprocess waste carpet fibers into carpet padding [source: Granger]. The Carpet Cushion Council tests and certifies padding that offers minimal emission of potentially toxic gases [source: Carpet Cushion Council Green Label].

Carpet Pad: Flat Rubber

Flat rubber has long been considered the premium carpet pad. Though composed of the same material as waffle rubber, flat rubber padding requires no molding and no air pockets in its production. The pads are solid and heavy in weight, so they aren't as soft as some pads. But they are long-lasting and give the carpet good support.

Flat rubber is an excellent pad for high traffic areas in your home. It resists furniture indentation and will not bottom out under heavy use. It's a good choice for hallways, stairs and other areas that need to stand up to a lot of wear and tear.

Flat rubber does not need to be as thick as other pads to provide adequate cushioning.

The HUD standard for flat rubber is only 0.22 inch (5.59 millimeters) in all traffic areas. The recommendation for light or moderate traffic areas is a density of 18 pounds per cubic foot (288.3 kilograms per cubic foot). For heavy traffic, 21 pounds per cubic foot (336.4 kilograms per cubic meter) is recommended [source: CarpetInspector.com].

Flat rubber has always been more expensive than foam padding. But rubber will last longer and is the only padding that may not need to be replaced when you purchase a new carpet. Because it's more commonly used for commercial applications, it's not available in all retail carpet stores.

Some consumers choose flat rubber for very high traffic areas or because they prefer a firm feel to their carpet. Others like that rubber has no VOC off-gassing and can be made from sustainable resources (natural rubber). Rubber also tends to be antimicrobial, so dirt and dander that work through the carpet are less likely to breed germs.

In the next section, you'll read about the material that went into the very first carpet pads.

Carpet Pad: Fiber Cushion

Fiber is the oldest type of carpet cushion. It was originally made from animal hair, a byproduct of the tanning industry. The hairs were pressed into a felt mat, which could be impregnated with rubber. When hair became less available, other materials like jute and recycled textile fibers were used. Today, synthetic fibers like nylon are commonly used to make fiber cushions.

Fiber mats aren't generally used for residential carpet installation, but they can be ideal in certain situations. In homes today, they are mainly laid down under area rugs to prevent their movement. They're more common in commercial situations to provide a very firm foot feel under carpets.

As with any pad, density is key to choosing the right fiber pad. Here are the HUD recommendations:

Rubberized hair or jute --For light or moderate traffic: 0.27 inch (6.86 millimeters) and 12.3 pounds per cubic foot (197 kilograms per cubic meter). For heavy traffic: 0.375 inch (9.525 millimeters) and 11.1 pounds per cubic foot (177.8 kilograms per cubic meter).
Synthetic fiber -- For light or moderate traffic: 0.25 inch (6.35 millimeters) and 6.5 pounds per cubic foot (104 kilograms per cubic meter). For heavy traffic: 0.30 inch (7.62 millimeters) and the same weight requirement used for light traffic.
Recycled textile fiber -- For light or moderate traffic: 0.25 inches and 7.3 pounds per cubic foot (117 kilograms per cubic meter). For heavy traffic: 0.30 inch and the same weight.

[source: CarpetInspector.com]

Fiber padding has some drawbacks, though. Natural fibers can rot if they get wet, and dampness can be a problem that makes your carpet pad smell bad. Using spun nylon and other synthetic fibers can prevent these issues. You should always go with synthetic-fiber padding if you're using it in a basement or on concrete.

Read on for lots more information about carpet padding.