What Is a Scarf Joint?

Scarf Joint

• The scarf joint is a fairly unique joint, in that it is often not a joint at all, but merely a way for two pieces of wood to be joined together via some other device, such as a nail or glue. In a scarf joint, one end of a piece of wood is cut on an angle. If the wood in question is a crown molding, for example, you would cut from the surface of the molding towards the back, at an angle so that the end of the wood formed a wedge. The other piece of molding is then cut at the opposite angle so the two angled ends fit together. Glue or nails are then used to hold the joint together.

Uses

• There are many different uses for a scarf joint. As demonstrated in the example above, one use is crown moldings. Finishing in general, which is all the more delicate wood work that goes on inside a framed and drywalled house, often makes use of scarf joints because they minimize the visibility of the joint. Another use of scarf joints is in antique, wooden airplanes, where glue can be used in place of nails to reduce weight.

Drawbacks

• There are several obvious drawbacks of the scarf joint. One is that unlike many other joints, the scarf joint is not designed, in and of itself, to hold wood together. The two pieces must be joined by either applying glue or by nailing through one diagonal cut in to the other. As a result scarf joints are often relatively weak, or rather they are only as strong as the nail or glue holding them together.

Similar Joints

• There are a number of joints similar to the scarf joint that could be used in place of it in certain situations. The tongue and groove joint, for instance, is a joint commonly used with wood floors. Every piece of wood flooring has a tongue, or protrusion on the front of the piece of wood, and every piece also has a groove, or hollow in the rear of the piece of wood, for the groove of another piece of flooring to fit in to. Another similar joint is a half lap, where half of the thickness of two boards is removed, and the two half pieces sit on top of each other, creating a level surface.