Frames
The life of a piece of upholstered furniture begins with its frame.
Although the underlying wooden framework cannot be seen in the finished product, the type of wood used to create it will have a bearing on the quality of the final product.
Some furniture employs softwoods, but may suffer from its difficulty in supporting the joinery that is required for the best quality furniture. The tight graining of hardwoods allows for pegs, screws and nails to be set securely, reducing the likelihood of their becoming loose over time. Hardwoods used in upholstered furniture include oak, alder and other woods with tight graining. Hardwood laminates are often used for blocks and braces because laminates are actually stronger than solid wood in these applications.
Most wood employed in upholstered furniture is kiln-dried. In this process, the wood is heated in an industrial oven to remove excess sap and moisture (and reduce its tendency for absorbing any moisture in the future), which can cause frames to warp, swell, shrink or change shape, or to succumb to rot or mildew, during their life.
The wood for a piece of upholstered furniture must be assembled into a sturdy frame. Generally, the more rigid the frame the better, because a loose frame can crack or fail, and several craftsman processes can be used to create a good, strong frame. A variety of woods and laminates are used for joining, blocking and doweling and sometimes several techniques are used.
Joints are the places where one piece of frame wood intersects to another part of the frame at an angle. Joints must be reinforced with blocks or dowels for extra support or the frame will be susceptible to loosening over time.
Blocking refers to the process of placing additional blocks of wood behind or diagonal to joints and corners for support in areas where the furniture craftsman believes there may be greater stress. Blocks provide lateral support and a larger area for screws and fasteners to set wood elements securely. This extra bracing at stress points contributes to the lasting integrity of the frame. An alternative to blocking is doweling.
Doweling refers to the process whereby one or two dowels are drilled, hammered and glued into the wood at stress-points to provide extra strength and support to the frame. Nails, screws, fasteners and glue may also support many parts of a frame.