Mortise and Tenon: Definition & Tools

Instructor: Christopher Muscato

Chris has a master's degree in history and teaches at the University of Northern Colorado.

In planning and constructing a structure, the joints can make the difference between success or failure. In this lesson we'll explore mortise and tenon joints and see how they are used to create strong structures.

Building Joints

When we talk about our physical health and in particular our exercise habits, there are a few topics that will commonly come up in conversation: muscle growth, weight loss, and what a drag working out really is. But what we don't talk about is that while we can put all the effort in the world into building a solid frame, it will be useless if we don't take care of the joints. Once the joints go, the strong foundation we have built will mean little. This is true of our bodies, and is also true of the structures and other things that we build. Joint work may not be the most glamorous aspect of construction, but it's just as important as any of the others.

The Mortise and Tenon Joint

There are literally hundreds of joints you could use to attach various elements together, but this lesson focuses on one of the most basic. The mortise and tenon joint has been used consistently for millennia and is still one of the most common ways to connect two solid elements together.

In the simplest terms, a mortise and tenon joint consists of the end of one piece fashioned to fit into a hole in another piece. It's not rocket science, but it is practical, efficient, and appealing. While these joints are used in stone and metalworking, they're most commonly found in woodwork. One block of wood is cut so that there is a cylindrical or rectangular hole, called the mortise, that goes either fully or partly through it. The second block of wood is cut so that its tip, called the tenon, is the exact shape of the mortise.

The mortise is the hole and the tenon is the element that fits into it

Building a solid mortise and tenon joint requires a high degree of precision. The tenon has to fit snuggly into the mortise, so it must match it in width, length, and depth. If the mortise is a complete hole that goes all the way through the wood, the tenon will come out the other end, where it can be secured with a pin. If the mortise only goes halfway through the wood, then the tenon may be secured with glue or nails. In extremely precise building, the friction and pressure of the completed structure are enough to hold the joint together without pins or glue.

Mortise and tenon joint

The Historic Use of the Mortise and Tenon Joint

There are many ways to use the mortise and tenon joint, and it may be one of the oldest construction techniques in the world. Near the German city of Leipzig, archeologists discovered the oldest preserved wood-frame architecture in the world. These ancient houses, dating to about 7,000 years ago, were built with mortise and tenon joints. Later, the ancient Romans made heavy use of this technique in wood-frame construction and stonework. If there's any ancient cultures whose building practices you should take seriously, it's the ancient Romans. They built more temples, houses, forts, walls, aqueducts, arches, roads, and palaces than anyone in the ancient world.

Mortise and tenon joints are commonly used in wood-frame construction

Making a Mortise and Tenon Joint

Mortise and tenon joints are commonly used in all sorts of construction, so it's important to know how to make one. Now, there are literally hundreds of variations on this basic joint, each depending on the material and project, so we're not going to do this as a step-by-step manual. Still, there are a few basic guidelines to cover.

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