Although some carpets are sold with "padded" foam backing, better carpets and pads are sold separately. The material used to manufacture "built-in" foam backing is not very resilient and soon compresses. Unattached carpet pads vary widely in price and quality. There are three common types - rubber, bonded (rebond) and urethane. The longest lasting - and most expensive - is the kind made of rubber. Some refer to rubber pad as waffle-pad because of it's similarity in appearance to the breakfast food of the same name. Rubber pad is of such high quality that it can be used over and over again under several generations of new carpeting. Unfortunately, rubber carpet pad is expensive $8 to $10 per square yard. Rebond pad is about half the price.

The latter is composed of colored chunks of foam glued together and has a reasonably long life span. Its lasting quality and competitive price make rebond the top seller. We often see rebond pad reused under a second generation of carpet, but most folks in the flooring business suggest replacement along with the carpet. Some people use thick pad to soften the blow between their foot and the floor. Not a bad idea until the carpet starts to stretch. Padding that is too thick can damage a fine carpet. Also, you can void a carpet warranty by using a pad that is too thick. Purchase pad by its density rating - pounds per square foot of density. And stick with a thickness between three-eighths and a half-inch. Half-inch 7-pound rebond pad is one you might like, or half-inch 8-pound. Some carpet manufacturers specify the pad that best fits their product. Since warranty and lasting quality are at issue, pay close attention to the manufacturer's recommendations. A pad that is too thin can be equally bad. Thinner pads will collapse more quickly and allow the carpet to fold and wrinkle.

Caution: Urethane foam pads are more uniform looking and feel great at first, but with use - especially in heavily trafficked areas they tend to compress and flatten quickly.

The proper carpet, the correct pad and proper installation all are critical to a good job. Seams should be joined with a 3-inch hot melt tape 6-inch is better and wood tack strip should be used at the perimeter.

Carpet in the bathroom is not something we suggest, but if you must, be sure to underlay the area with sheet vinyl, then pad, then carpet.

Don't forget these simple carpet-shopping rules:

Carpet is sold by yarn weight (ounces of yarn per square yard), density (number of tufts per inch in each of two directions), and yarn type (nylon, rayon, wool, etc.).

The Federal Housing Administration requires carpet to be a minimum of 24 ounces in weight for any home that it finances. Other factors such as yarn length, yarn twist, and backing material can also alter quality as well as price somewhat. A good yarn weight will run between 30 and 40 ounces with higher-end carpets running in the 50- to 60-ounce range. Tuft density in most carpets will run about 10 to 11 tufts per inch. More tufts per inch make for a tighter nap, or denser carpet. Low-cut pile carpets will be lighter than high-cut pile ones when the density of the two is equal.

Nylon is one of today's best buys. Nylon, and a factory-applied coat of Scotch Guard, is a winning combination. Wool is also nice - and easy to clean - but can be expensive.

Bottom line: Look for a Scotch-Guarded nylon low-cut pile carpet assembled at 10 to 11 stitches per inch that weighs about 40 ounces per yard. It will feel dense to the touch, resist abuse well and last for years. Have it laid on a 7- or 8-pound half-inch thick rebond pad and ask for the widest seam tape that the installer offers. Be sure to retain a few small scraps of the carpet for patches in the event a spill causes a permanent stain.

Carpet lasts longer when it is kept clean. If you really want a long life for your carpet, vacuum once a day.

Carpet odor is a reason why many people prefer hardwood, linoleum, tile or stone. Carpet easily can be deodorized by sprinkling a box of baking soda onto the affected area. Leave it on through the night, and vacuum it up the next day.