A sofa is one of the biggest furniture investments you’ll make — and one of the most permanent. Even if you’re just buying one for a temporary fix, it’ll eventually get demoted from the living room to the family room to the basement and, finally, the dorm. Before you know it, a decade or more has passed, and that impulse purchase has become part of your life. So give some thought to it before you buy. Then buy the best-quality sofa that you can afford. Your purchase will be amortized over many years.
Test its sturdiness. Quality sofas should feel solid and heavy. Flop around on one to test its sturdiness, then lift it up by the corner and shake it a bit. If it feels light or wobbly, take a pass. Look for a frame made from a kiln-dried hardwood such as oak, alder, birch, maple or, alternatively, high-quality hardwood plywood or marine plywood. Eight-way, hand-tied springs are a hallmark of fine furniture, but sinuous S-shaped springs can provide nearly as much comfort. Drop-in coil springs are a less costly alternative.
Check the joints and frame. The best sofas have joints that are double doweled and fitted with corner blocks that are both glued and screwed (not stapled) into place. Quality pieces have legs that are part of the frame, not just attached to it (although removable feet do make it easier to get items through doorways).
As a rule, synthetic fabrics are more durable, colorfast and cleanable. Tightly woven fabrics and fabrics that are heavy will stand up to wear and tear better, as will leather. Avoid satins, brocades and damasks unless the sofa won’t get much use.