The easiest of all trim joints to create is the butt joint. The end of one piece of trim is simply placed flat against the side of the the other, and then the edges are affixed to the wall with painter’s caulk.

A butt joint is used where two pieces of trim with a square profile come together, such as at an inside corner; where a side casing meets a window stool, plinth blocks,or the floor; or where a thinner piece of molding meets a thicker piece.

Do not use a butt joint for an outside corner because the exposed end of the one piece cannot be finished in any way that will make it attactive.

Though a butt joint is simple to make, the best join with no gapping whatsover. In fact, there should be no visible line without close inspection. While caulk can close up a small gap, it is better to cut the joint to fit tightly (the caulk will also fail over time).

Fit the pieces together, then make the necessary adjustments in the mating piece and continuing test fitting until it fits snugly to the face of the other piece of trim.

Photography copyright Sunset Publishing Corporation