What Is a Plinth Block & How Is It Used?

Plinth blocks sit at the bottom of a door casing.
Plinth blocks sit at the bottom of a door casing. (Image: Brand X Pictures/Brand X Pictures/Getty Images)

Plinth blocks act as transition pieces between door casings and baseboards. They typically appear at the bottom corners of door casings, or the wood trim that surrounds an entryway. Without plinth blocks to act as transition pieces, workers would be forced to butt door casings and baseboard trim against one another.

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Casings and Baseboard Trim

Narrow panels of wood trim often line the borders of entryways. The wood trim, known as door casing, provides a finished look to the edges around a door frame and covers the jagged edges of the wall around the door. Baseboard trim, on the other hand, lines the bottom of walls, hiding the gap between the walls and floor. The two types of wood trim meet at the bottom corners of an entryway.

Transition Problems

Both door casings and baseboard trim come in a variety of styles and thicknesses. Creating a smooth transition between two types and thicknesses of trim is difficult. For example, if a home’s entryways are wrapped with ornate wood trim but the baseboard trim is comparatively plain, workers might not be able to merge the disparate designs in an eye-pleasing way.


A plinth block is a rectangular piece of wood that solves the transition problem. Generally, its top edge sits higher than the baseboard trim, and its thickness exceeds the thicknesses of both the door casing and baseboard trim. Allowing the plinth block to jut out slightly masks the relative differences in thickness between the casing and baseboard trim.


Choose a plinth block that creates a pleasing segue between the styles of trim around your doors and the lower part of your walls. Often, plain plinth blocks are the most effective, but you might prefer an ornate design. If possible, lay your trim choices next to one another for comparison before installation to ensure you’ll be pleased with the final results.


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