Strategies For Building Stronger Furniture
Strategies drawn from structural engineering solidify your furniture
Synopsis: Building a long chest of drawers with legs at each end but no supports in between doesn’t require an engineering degree, but it does require an understanding of the forces that act upon a piece of furniture. When commissioned to build a chest of drawers slightly over 6 ft. in length, Mike Korsak had to figure out how to design such a long case so that the drawers, when loaded, do not sag. His solution was to stiffen the structure with diagonal braces, L-section aprons, and a rigid back that turns solid back panels into beams while still permitting them to move with the seasons.
I am not an engineer, but I developed a good sense of loads and structure when I spent several years as a designer of timber-frame structures. Buildings framed with huge timbers may seem like distant cousins to furniture, but they aren’t far removed. Understanding the forces acting on a piece of furniture is much like understanding the forces acting on a building.
When I received a commission to build a chest of drawers slightly over 6 ft. in length, my first thought—after roughing out a design with 10 drawers and no supports between the legs at each end—was how to deal with the loads created by all those heavy drawers. My primary concern was deflection, or sagging, which could change the shape of the drawer openings, leading to drawers that don’t fit their pockets. Not acceptable! I’ll outline here the approaches I used to construct a case that could withstand that load across a long, unsupported span. You can adapt the ideas to casework of any size or style.
I stiffened the structure in a variety of ways: adding diagonal braces, L-section aprons, and a rigid back that turns solid back panels into beams while still permitting them to move with the seasons. The diagonal braces were the biggest game-changer—they greatly stiffened the case but also altered the load path, leading me to strengthen the back to compensate.
The front and rear aprons are main load-carrying members, so I designed them to be very stiff. The curving bottom edge of the apron, flowing and asymmetrical, might add a whimsical note to the chest, but engineering influenced its design. I located the tallest part of the apron at mid-span, where the potential for deflection would be greatest; and I let the apron narrow down where it meets the legs. This might seem counterintuitive, but the internal stresses that cause deflection in a beam are generally highest at the center of a span.
For the full article, download the PDF below.
More on FineWoodworking.com:
- Bold joinery for casework – Make your cabinets stand out with clean, attractive through-tenons
- Hudson Valley Chest of Drawers – Tasteful moldings and turned feet add quiet style to a sturdy dovetailed case
- Engineer Shelves With The Sagulator – Online calculator determines thickness and length to prevent shelves from sagging