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.