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What Goes Under Carpet?

A collage of carpet's inside components.

If you have ever watched a carpet installation or ripped up carpet to it replace it, you saw that in addition to the carpeting, a layer of gray or yellow fabric laid beneath it. You saw the carpet underlayment, also called carpet padding or carpet pad.

This padding or underlayment adds a carpet cushion beneath the carpet that protects the flooring beneath it such as hardwood or laminate flooring and adds to its thickness and comfort.

Related: What is Carpet Remnant | Types of Soundproof Carpeting | How to Make Your Carpet Fluffy Again | Should You Have the Same Carpet Throughout Entire House 

Carpet Padding Types

Many different types of this carpet underlay material exist, but you will typically find seven kinds for sale at carpet stores. These varieties span a range from inexpensive to specialty which costs quite a bit.

Urethane Foam

This is a close look at a sheet of polyurethane foam.

Urethane foam pad costs so little to produce that most stores give it away to customers when they purchase carpet. The cheap stuff typically flattens completely after just two years, and you will probably think that you need an odor new carpet when really, the pad went out.

Of course, you have no option to replace the padding without pulling out the carpet, so you at the very least end up pulling up everything to replace the padding.

Rebond Pad

Most of the underlayment you walk on is rebond pad. According to the Carpet Cushion Council (CCC), 85 percent of the padding on which you walk is rebond pad.

This recycled product comes only in multicolored, but no worries since you will never see it beneath your solid-colored carpet. It comes in a variety of densities and thicknesses. The cost of these ranges between $0.39 and $0.45 a square foot.

Frothed Urethane

This varies vastly from urethane foam. This frothed option provides this most durable pad made. Its manufacturing process includes injecting gas into liquid foam. You can re-use this frothed foam pad for two high-quality carpet installations.

Waffle Rubber Pad

No, you do not pour syrup on this option, but it did get its name from resembling the tasty breakfast treat. Its quality resembles that of rebond pads, but this option costs a little more than they do. Frothed urethane beat both options for durability. If you find it on sale for less than rebond, snap it up.

Memory Rubber Pad

When you have the money and want to feel as if you walk on clouds, invest in a memory rubber pad, also called memory foam pad. It gets made from the same material as memory foam pillows and mattresses.

Using this as underlayment for your carpet essentially provides the coziest, most comfortable carpeting. It costs a bit more than rebond padding and does not provide as eco-friendly a solution since it doesn’t use recycled materials.

Fiber Pads

Fiber pad.

Fiber pads work best with Berber carpet. The thick, dense fibers of these pads make this padding solution extremely durable.

They are manufactured from felt, nylon, polyester, and other materials that provide a durable, yet inexpensive carpet option. It also works best with high-traffic areas requiring carpet, so it is ideal in commercial settings.

Special Pads

Sometimes, you need something special because you have a unique situation. Here, you apply a specialized carpet pad. You might need this in situations requiring air filtering, odor removal, or moisture barrier padding.

Making Throw Rug Pads

Each of these carpet cushioning options forms a vapor barrier whether they use bonded foam, frothed foam, or rebond pad. You can purchase these items by the square foot, so you can obtain just enough to trim to go beneath a throw rug or Oriental rug as a rug pad. These are typically made of foam pads.

Frequently Asked Questions

Why does carpet padding thickness matter?

With too thin of a pad, you do not add to the carpet’s cozy, cushiony feeling. Some carpets do not need this though. With Berber carpet and short-pile carpet, you need a thinner pad because a thick pad creates too much give and damages the underside of the carpet.

Carpet pad thickness does not typically increase cost, so there’s no reason for a carpet salesperson to steer you wrong on this. Ask them which pad would work best.

How is pad density measured?

You will read it listed two different ways — pounds per cubic foot or ounces per square yard. Typical padding ranges from three to 10 pounds. To maximize how long your carpet lasts, choose at least a 6.5-pound rebond pad.

For a foam pad, you would need a two to five-pound pad; for a frothed foam pad, you would need a 12 pound; for a synthetic fiber pad, choose a 30-ounce pad; for a waffle rubber pad, choose a 90-ounce pad; and slab rubber pad which should weigh 21 pounds at least.

Do you only use carpet underlayment under the carpet?

No, you also use forms of this underlayment under hardwood floors and throw rugs. Under hardwood floors, you will need an underlayment with acoustical properties. This helps to reduce sound transmission.

To what does the Impact Insulation Class (IIC) rating refer?

The IIC rating refers to a measure of the reduction in sound transference when you walk on a floor surface.

What is eco cork?

Eco cork refers to a foam underlayment used in installations of laminate, wood, and vinyl flooring, but not in carpeting. It blends granulated cork and polyethylene to provide a waterproof underlayment featuring a built-in 6 mil vapor barrier. You can use eco foam for concrete or wood sub-floors.

What concerns are there about re-using carpet padding?

The carpet underlayment or pad may retain stains and odors from spills that occurred on the carpet you just pulled up. Its age and the situation in which it was used depend on whether you can re-use it. 

What happens if you skip the underlayment or padding beneath a rug or carpet?

Your carpet or rug will not last without a good pad beneath it. Woven fibers attached to a backing form the rug or carpet. The pad beneath it supports the carpet’s backing, so it does not break when walked upon.

The pad helps the carpet age less quickly and reduces fiber wear. Without a pad under the carpet, it tears up and may not last even one year.

Are any of the carpet pads really pet urine resistant?

Some carpet pads do provide waterproofing. That means that when you spill something on the carpet above it, the pad does not saturate. It pools the spill which never reaches the flooring beneath it.

The same thing happens when your cat or dog pees on the carpet. The pad stops the pee from reaching the flooring. It also stops the carpet pad from absorbing it. You would be able to clean up the carpet spill without it absorbing into the other layers.

This makes it simpler to clean up pet urine. The only odor you would need to treat was the one in the top layer which makes cleaning simple.