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.