Fabricating curved wood millwork is one of the most demanding tasks the carpenter faces, especially when the bent woodwork is to be exposed to the outside elements. Built in the late 1990s, the trim on this curved wooden fence did not stand the test of time. Furnishing privacy in a quiet Brattle Street neighborhood, it was rotted, infested with carpenter ants, and coming down on its own, with or without help.
The owners stated that if past performance was indicative of future results, they would prefer to redesign the fence, removing the curve, rather than invest in such a short replacement cycle. We told them no problem, we could fabricate a durable replacement and, considering the cost of replacing the curved masonry retaining wall below, it would be cheaper to do so.
The rapid failure of the curved elements was caused by two optimistic choices by the original builder. First, the builder assumed that finish grade white pine would perform in this application. It did not. And second, the builder used a naive method for making the curve, fitting together a series of short, straight, finger-jointed pieces in order to describe the prescribed arc. These multiple joints produced multiple points for water penetration and rot.
For wood species, our carpenters specified western red cedar boards as both durable and well suited for the lamination method that they planned in order to produce the curve. These they ripped into pieces 3/16” thick. Thin enough, in other words, to bend. They sandwiched these thin “planks” six thick along the curve of the arc, saturated in wood glue, and clamped them tightly. By this method, a single, monolithic piece was produced.
When the glue had set up, the carpenters removed the clamping, and the curve held perfectly with zero twisting or other deviation. They sanded the joints to remove any accumulations of glue, and double back primed the pieces before assembly. After assembly, our painters applied three coats of paint to protect the installation.
In summary, it is a simple matter for a designer to draw a curved element, in pencil on a piece of paper, or in a design app, but it is the carpenter who must make it happen. There is something elating about the swoop of a curve, in wood, whether in a 21st century backyard or in a Victorian turret. It is a technical achievement, in either era.