Powerful New Joint: Housed Double Tenons
Housed double tenons are strong and simple to make
Synopsis: This strong, weather-tight joint takes care of the problem of moisture wicking into the end grain of tenon shoulders on a traditional mortise-and-tenon joint. The U-joint has no exterior shoulders; its only shoulder is hidden between twin tenons and set below the surface of the mortise, so moisture is not an issue. With four tenon cheeks instead of the standard two, it has greater glue surface and greater strength. Though he originally designed it for use in outdoor chairs, its maker Brian Boggs now uses it for chairs of all kinds, and even tables.
When I began building outdoor chairs 10 years ago, I searched for a strong, weather-tight joint. The traditional mortise-and-tenon works well for interior pieces, but outdoors, moisture can wick into the end grain of the tenon shoulders, undermining the joint. I designed this U-joint, with its only shoulder hidden between twin tenons and set below…