Joinery is the woodworking function of connecting two pieces of wood together. There are dozens of connection or joinery techniques, but for most home handyman, indoor and outdoor woodworking projects the following five joints are the most common. Depending on which joint method is utilized they run from a level of novice to intermediate woodworking skills.
If you are an expert
woodworker and looking for unique joinery for furniture or other fine woodworking projects I suggest you purchase a copy of "The Complete Illustrated Guide to Joinery".
- Butt Joint: Figure 1
Figure 1 - Butt joint
- Overlap Joint: Figure 2
The butt joint is simplistic. The end of a piece of wood meets another piece of wood with their surfaces butting up against each other. The butt joint can be used at the ends of both boards or one can be an end and the other can be anywhere along its length.
The butt joint has no mechanical strength and its holding power is determined by the screws, nails and/or adhesives used to hold it together.
Butt joints are used extensively in rough-in or framing carpentry when two pieces of lumber meet. The joint is usually held together with large nails.
A butt joint does not have to be made on a 90 degree angle. Many picture frames use butt joints on a 45 degree angle.
To make a butt joint, the end or ends of the lumber must be cut perfectly square. A back saw and miter box is usually sufficient to create the square cut. For rough-in carpentry a power circular saw will work fine. If you have many butt joints to make you may wish to consider using a power miter saw.
Figure 2 - Overlap joint
- Through Tenon Joint: Figure 3
The overlap or lap joint requires that half of the thickness of each of the two pieces of lumber that are coming into contact with one another be removed. When the joint is completed the joint is the same thickness as either one of the boards. The overlap joint can be used at the ends of boards or anywhere along their lengths.
The overlap joint provides much more surface area for adhesives than a butt joint, hence the joint is stronger. An overlap joint in the middle of lumber can be quite strong, providing external forces are not trying to separate the joint through a twisting motion. The addition of screws or nails through the overlap will provide additional strength.
An overlap joint can be created and used at any angle.
Although an overlap joint can be made with hand tools; backsaw and chisel, in most cases a dado blade in a power circular saw or table saw or a router would be used to create the joint.
Figure 3 - Through tenon joint
The through tenon joint requires the removal of one third of the surface area on each side of the end of one of the boards to be joined and a notch or slot equal to one third of the area of the other board in the center of the end of the board.
The through tenon that was created in the first board rests in the slot that was created in the other piece of lumber.
A through tenon joint provides more surface area than a butt or overlap joint for adhesives. It is stronger than an overlap joint and is used when joining the ends of two boards together.
This type of joint is common in better quality wood gates.
Additional strength can be added to the joint by using nails, screws or doweling through the joint itself.
The through tenon joint can be made using a back saw and wood chisels. However, a dado blade on a table saw is much more efficient method of making a through tenon joint.
The through tenon joint is only used at 90 degree intersections of two boards.