What you’ll need to make a torsion box

The top photo shows the assembled parts and materials needed to complete any torsion box: core pieces, skins, glue, glue gun, location blocks, clamping battens and cauls. The core is connected by staples. A spring-action stapler or pneumatic gun can work equally well (above).

A torsion box is a grid of core material made to whatever thickness you want it to be with a sheet of manufactured sheet stock glued to each face. It offers woodworkers at least three advantages.

First, it allows for the manipulation of the thickness of the parts of the piece. Whereas just about any length of solid wood can be obtained and any width can be achieved by gluing pieces together, the thickness of parts is typically 3/4". Call it “the 3/4" Syndrome.” A thickness planer allows one to easily go thinner, but going thicker quickly raises the cost, and going much thicker, say, beyond 2", confronts one with the considerable problems of availability, stability and weight.

The second advantage is that it is very light for its size and dimensionally stable.

Third, the inherent strength of the system can be used to develop furniture forms that are not possible using solid wood. For example, imagine a long dining or conference table. Fitting it with a solid-wood top requires the making of a two-part structure: an underframe that supports the top while allowing it to shrink and expand. Now make the top as a torsion box. Because it is inherently strong and dimensionally stable, the legs or pedestals can be engineered into it.

The top becomes the structure that carries the legs or pedestals, the very opposite of the solid-wood example.

Torsion boxes can be used in practically every furniture form —storage cases, shelving units, tables, beds and all forms of seating, upholstered or not. In terms of workmanship, the torsion box is as demanding as working in solid wood. In fact, it requires more rigorous planning, because once a torsion box is glued up, it can’t
be altered easily.



A torsion box gets its strength from its structure. Any twisting or bending force applied to a torsion box is converted into shear stress on the glue lines between skin and core — the very type of stress a glue line is best able to withstand. Any of the polyvinyl acetate glues, white or yellow, will work well in this application.

If you calculate the glue line contact in a torsion box, the result may surprise you, but it explains why the constructions so rigid. For example, a 2' x 2 torsion box with 1/4"-thick skins and a 1/2" core that is on 4" centers has a total glue surface area of about 320 square inches, an impressive figure.