Inner Construction

The construction and inner workings of an upholstered piece of furniture can be as mysterious as an episode of Murder, She Wrote (Ask your Grandma). But hidden under the decorative fabric or cover lies the secret to the piece's overall function, comfort, and longevity. No need to call Angela Lansbury in to solve this case, read on as we uncover what makes your chair or sofa tick.

The frame is the single most important component in determining whether or not a piece of furniture is going to stand the test of time. You probably figured wood as being the most commonly used frame material, and this, of course, is true. But any old hunk of tree won't due if you plan on passing this wonderful chair, sofa, love seat, or whatever on to your children or grandchildren (they'll probably just put it in storage or sell it at a yard sale anyway). Hardwoods, such as oak, alder, ash, beech and birch are what you're looking for in a frame. These hardwoods have a tighter grain and allow for screws, pegs, and nails to be set securely. Also, the best-made frames use wood that has been kiln-dried. This process consists of heating the wood in an industrial oven to remove excess sap and moisture. The process also makes the wood resistant to absorbing any outside moisture. If you're wondering what the problem is with moisture, I'll tell you. If you already know the answer to this then skip down a little Mr. or Mrs. Smarty-Pants. Moisture can cause warping and swelling, can lead to loose joints and fastenings, and in severe cases can cause mildew or rotting, other than that, it's great.

The quality of the frame depends not only on the materials used, but how they're joined and held together. To create a strong, rigid frame, a variety of woods and laminates can be used in joints and for blocking and doweling.

• Joints are places where one piece of the frame meets another. These points of intersection need to be secured and reinforced with blocks and dowels to allow the frame to hold up over time.
• Blocking refers to placing additional 'blocks' of wood behind or diagonal to joints and corners to help relieve the stress these areas encounter. Blocks also provide lateral support and create a larger area for screws and fasteners to set wood elements securely.
• Doweling is the process of drilling into both pieces of the joint and then placing a pin, or dowel into the hole, thus further connecting the two pieces and adding extra support.

A quality chair or sofa will employ some type of inner spring system, usually in the back as well as the seat area. These systems add comfort, as you might expect, but they also work to take some of the stress off the joints of the frame. Here are some of the spring systems being used:

• The coil or cone spring system uses eight-way, hand-tied double cone springs to provide extraordinary comfort and support. This technique involves fastening the cone springs tightly to the base and expertly tying their tops together with a strong cord. This is the only system that allows for side-to-side movement in addition to up and down movement. Hand-crafted quality comes at a price, though, and while this is widely considered the best spring system, it is also the most expensive.
• The sinuous wire spring is made in a continuous zigzag or "S" shape. These wires run parallel to each other and are fastened directly to the frame and to each other. Similar to this system is the formed wire spring, whereby the continuous wire is formed into rectangular bends and angles instead of the zigzag pattern.
• The grid suspension system is composed of a wire grid, sometimes covered with paper or plastic-coated wire, which has one side fastened directly to the frame. The other side is connected to the frame by helical springs.
• Some manufacturers use elastic webbing instead of wire springs. The strips of elastic usually intersect and weave together and are fastened directly to the frame. It is best to avoid furniture that uses this technique.