Sofa construction varies depending on whether it is a high-end or budget piece. Although both high-end and more inexpensive models have their place, knowing the difference will help you when shopping for a new couch.
Web suspension is a design that creates a sofa cushion support similar to a hammock. Webbing can be made of elastic bands, or out of natural fibers like jute. The bands of webbing are traditionally manufactured about two to three inches in diameter. The strips are stretched across the seating frame and tacked into place to provide support for the cushions. Webbing is the least favorable and most inexpensive method of construction. It may not last as long as spring construction, but it also eliminates the discomfort some springs can cause by poking through cushions.
Light-Gauge Metal Springs
Some manufacturers use a light-weight metal spring system for the seating and back support on sofas and chairs. These may be mass-produced units that simply drop into the couch frame. They have the distinction of being noticeably bouncy when the user sits, and can weaken and sag considerably over time.
S-springs are so named due to their sinuous or serpentine spring construction. They are in the shape of an S. These sinuous springs are constructed much closer together than some of the more-inexpensive spring supports. A heavier-gauge steel is used in construction, and a greater number of springs with few spacings provides more even, comfortable support.
The ultimate choice in high-quality sofa construction is the eight-way hand-tied springs. This type of construction utilizes heavy-gauge steel coils as a base. A craftsman then works with a high-quality twine to tie each coil spring together with the adjacent springs and to the sofa frame. As the twine is tied, it is crossed in eight different directions. This process helps guarantee sturdy support and limits individual sagging of any one spring over the life of the sofa.
While spring construction, and particularly an eight-way hand-tied spring construction is considered the high-quality choice over webbing, there are merits to either choice. For a simple sofa at a low price point around $500 (in 2010 dollars), webbing is a fine choice when the sofa only needs to stand up to comfortable, occasional use. If you come with a higher budget--over $500--and a need to support kids, pets and lots of activity, choose spring construction.