Types of wood joinery

Have you ever noticed how some of your furniture is assembled differently from others? Perhaps some has legs that are bolted on, while others have slots for the legs. Or maybe you’ve noticed a different type of joint in your cabinetry (the dovetail, which we’ll talk about later). There are many factors that go into the decision of how to join different pieces of lumber together. You can read about some of those reasons here, and learn more about some of the most common types of wood joinery.

Butt joint

A butt joint is when two pieces of wood are joined at 90 degrees, or perpendicular, to each other. These joints can be fastened with nails, screws, dowels, biscuits (small football shaped inserts; you can read more about these below), or glue. If only glue is used, the joint could become weak if not properly prepared, because the end of a board will absorb most of the glue and will not leave much on the surface to adhere to the perpendicular piece. Because of its simple, rough aesthetic, a butt joint is a good choice for a project in which appearance is not a concern; or when a simpler, perhaps rustic, look is desired. If you have viewed our gallery, you may have seen a butt joint in the reclaimed wood cabinet project.

Miter

A miter joint is similar to a butt joint, except that the two ends being joined are cut at 45 degrees. These joints are much more aesthetically pleasing, which is why you’ll often see them used in furniture and picture frames. Miter joints should generally not be used outdoors though, since the wood movement caused by weather tends to create gaps. In terms of joinery, miter joints tend to be weaker than many other types of joints, although they can be reinforced using other methods. You can view a miter joint in the barnwood coffee table I previously made and the custom shell display case.

Half-lap

A half-lap joint is when two boards overlap at a corner. At the corner where they overlap, half the thickness from each board is removed, so that when laid on top of each other, they still equal the same board thickness. The overlapping area is then secured with glue, screws, nails, or pins. These joints have a similar appearance to butt joints, but are much stronger, because of the large surface area that overlaps each board. A different type of half-lap joint is a cross half-lap. In this joint, the boards cross over each other diagonally, so the overlapping sections are made in the center of the boards, rather than the ends.

Dovetail

Dovetail joints are very common in quality woodworking. In this joint, there are pins and tails. At the end of one board, the pins are cut. These are finger-like protrusions from the board, which have their vertical sides cut at a slight angle. The other board has tails cut into it, which are notches that the pins fit into. A dovetail joint is most commonly used in drawers since they are very durable and do not come apart easily. The use of jigs has made it easier to create these, and therefore they are becoming increasingly common. There are also many other variations of dovetail joints, such as half-blind dovetail, secret mitered dovetail, and secret double-lapped dovetail.

Mortise & tenon

A mortise and tenon joint is essentially a slot-and-peg system. The tenon is a rectangular tab that is cut at the end of a board. This tenon is cut from the same material as the rest of the board, which lends to this joint’s strength. The mortise is a hole in a different board, which the tenon will be slotted into. The mortise is the same size as the tenon, and the two should fit together snugly. This type of joint has been used for thousands of years, as a peg can be added through both the mortise and tenon, creating a mechanical joint (before the invention of screws, nails, and glue).

Bowties

A bowtie is a type of joint most commonly used when a piece of wood has begun to split or crack. A lot of times, wood in its natural state is highly desirable, including any cracks that may be in the wood. While these may be aesthetically pleasing, it is important to stabilize the split in order to maintain the integrity of the rest of the piece. To do this, the craftsman will first cut out a piece of wood in the shape of a bowtie. Then, that exact shape is carved out of the piece of wood that is splitting. The bowtie is then inlaid into the split wood and glued in place. The bowtie straddles the split, giving strength to the joint and not allowing the split to expand any more.

Dowels & biscuits

Dowels & biscuits are joinery techniques which you should almost never be able to see in a finished piece. That’s because both of these methods involve joining pieces together from within the lumber. Dowels are short, round pegs that are inserted into holes that have been drilled into the wood. Only half of the dowel length is inserted into the first hole. The other half will be used in the adjoining piece. A matching hole is drilled in the other piece of wood to be joined, and then the other end of the dowel is inserted into the adjoining hole. Biscuits use a similar method of joining, except rather than a hole, a slot is cut into the lumber. Because these slots are wider, small football shaped pieces of wood (biscuits) are inserted and glued. There are some exceptions which you will see dowels or biscuits in a finished piece. Sometimes, the craftsman will use these as accents, on the joining edges or corners of a piece.