When furnishing a family room, many parents figure they can use the old ratty sofa they've had since college and buy a new one for the living room where it won't get messed up.

But it's more sensible to put the new one in the place where you'll be spending most of your time, and more sensible still to get a good one that can withstand the rigors of child rearing while serving a multitude of functions -- eating, napping, roughhousing and reading.

The sofa also should be comfortable, Silver Spring interior designer Deborah Wiener said.

She recommends one with a sturdy hardwood frame, a "spring down" seat (the seat underneath the cushions has steel coiled springs that are wrapped in down and covered in Dacron) and down-blend wrap cushions (the back and seat cushions have a high density foam core that is wrapped in down and also covered with Dacron).

Comfort also depends on size. To accommodate the widest range of adult height and body shape, sofa seat depth can range from 18 to 22 inches and seat depth, 16 to 22 inches. The only way to know what's right for you is to go to a showroom and test the sofas until you find one that you can sit in comfortably, Wiener said,

If you're tall, standard sofa back height -- 34 to 36 inches -- may not be enough, but for an additional charge, many sofa manufacturers will raise the back two inches, Wiener said.

You need upholstery fabric that is stain-resistant and easy to clean.

The most durable upholstery fabrics are commercial ones. Because most commercial-grade fabrics are sold at design centers and not directly to the public, you will have to purchase one with the help of an interior designer or decorator. You can use the fabric on a sofa that the designer helps you select or one you buy yourself -- almost all sofa-makers will accept a "customer's own material" (usually referred to as COM).

You may wince at the thought of a polyester-covered sofa, but fabric manufacturers make synthetics that look and feel like natural fibers.

Bethesda interior designer Skip Sroka swears by a polyester chenille he has on his sofa. Not completely persuaded, I tracked down some samples of his Chinchilla by Arc-com, and found that it has a great "hand" (a fabric industry term for describing a fabric's softness) and great color selections as well.

The most foolproof upholstery fabrics are the commercial ones with added treatments that greatly enhance stain and moisture resistance (if there's no water resistance, spilled liquids can soak into the cushions, producing mold and unpleasant odors). Wiener recommended Crypton, which has been available for more than 10 years. Gore Seat Protection, which was introduced about a year ago, is less known. Both will work well in residential settings that include rambunctious children.

For residential use, the most significant difference between the two treatments is that Gore Seat Protection can be used on a wider variety of fabrics. Assuming that it gains wide acceptance among upholstery fabric manufacturers, consumers will have more choices.

How much do these wonder fabrics costs? Commercial-grade fabrics are a lot more expensive than residential grades. Retail prices for Arc-com, which offers both Gore Seat Protection and Cypton-treated fabrics, range from about $30 to $40 a yard. To cover a three-seat sofa and cushions takes about 20 yards; a two-seater takes 15 yards; and an ottoman generally takes three yards. This sounds pricey, but the fabrics are soft, the colors are gorgeous, and having one nice piece of furniture in the middle of a lot of chaos can have a tonic effect.

For more information on the Web: Crypton is at www.cryptonfabric.com; Gore Seating Protection is at www.goreseatingprotection.com; Arc-Com is at www.arc-com.com.

-- Katherine Salant