February 28, 2024
Two joinery details that are reshaping how modern timber frames are built.
Whenever two pieces of timber meet in a timber frame, they must be connected. Carpenters refer to this connection as joinery the precise shaping of mating surfaces that allows structural members to lock together and transfer loads effectively. Traditionally, most joinery details are concealed once the frame is assembled, quietly doing their work out of sight.
In this article, we highlight two joinery details that have had a meaningful impact on both the structural performance and visual refinement of modern timber frames. Enabled by advances in CNC technology, these connections represent a quiet but important evolution in timber framing.
Dovetails the dovetail joint has been used for centuries, valued for its inherent strength and mechanical locking action. It consists of a V-shaped tenon at the end of a timber that slides vertically into a matching mortise in a receiving beam. Dovetails are commonly used to connect floor joists to primary beams, but they can also be applied to purlins, corbels, and other secondary members intersecting larger timbers.
Tapered dovetail mortise in receiving beam
Improved tenon with double taper
This modern dovetail variation incorporates a double taper that draws the connected timbers tightly together as the joint is seated. The refined geometry increases surface contact and helps maintain a snug fit as the wood naturally responds to indoor humidity changes. The result is a joint that enhances both structural integrity and visual crispness strength and beauty working together.
Housed Mortise the housed mortise is an enhanced version of the classic mortise-and-tenon joint. It introduces a recessed shoulder around the mortise, allowing the incoming timber to sit partially or fully into the receiving beam or column. This housing provides additional resistance to rotation and lateral movement by increasing bearing area and improving load transfer.
Historically, housed mortises required significantly more labor and were therefore reserved for structures experiencing higher forces – such as mills, large civic buildings, or churches where their structural benefits justified the effort.
The housed mortise allows the incoming timber to be set fully into the receiving column.
With modern CNC timber cutting, the time and effort required to create housed mortises has been dramatically reduced. While many contemporary timber frame projects may not require their full structural capacity, these joints offer an added advantage: refined aesthetics. By recessing the connection, visible gaps between timbers disappear, creating cleaner lines and a more unified appearance.
If you’re considering a timber frame for your next project, we’d be happy to talk. You can reach us by phone at 204.377.5000 or by email at info@cstf.ca.
