how to extreme

Plinth Blocks

Construction How-To, Floors, Molding December 1, 2015 Sonia








By Rob Robillard

I love using plinth blocks in finish carpentry, especially when the door casings I’m installing have deep and ornate details.

Originally plinth blocks were masonry support bases, but have since evolved into more of a decorative add-on for many interior decors, adding a touch of style and class to a room. If you are in the process of upgrading your interior trim, consider adding plinth blocks to your doorframes.

Often referred to as “do-hickies” and “thingamajigs” by a customer of mine, plinth blocks act as a decorative base for door trim, pilasters or columns, and are often seen in higher end trim work and older homes where the trim and baseboard intersection do not visually meet well.

Plinth blocks stand proud at the bottom of the casing, adding a reveal and shadow-line depth between the vertical and base trim. Plinth blocks can be a wonderful visual element to virtually any room, adding a nice aesthetic detail to a molding, baseboard or door frame.

What Does Plinth Mean?

“Plinth” is an architectural term used to describe a support or base for a column. Plinth blocks are located on the floor and below door casing to create a transition to the baseboard. These molding pieces create a classic appearance to door surrounds and are commonly used with either rosettes or a door header, but can be used with mitered casing, too.

Base your plinth design on existing blocks throughout the home.

Base your plinth design on existing blocks throughout the home.

The plinth block should always be at least 2 to 3 inches taller than the baseboard, it must be thicker than both the casing and the base. It should be 1/4 inch wider than the casing.

When do you need a Plinth Block?

Usually when the door casing or architrave is thicker than the baseboard skirt, you do not need a plinth unless it is part of the design (or the lower part of the trim needs protection). If, on the other hand, the baseboard skirt is thicker than the casing, a plinth block is a good solution.

Sketch a template.

Sketch a template.

The Golden Rule for Sizing

For a plinth block to look right it needs to clear, or at least meet, the baseboard and base cap height. The other issue is proportion. Plinth blocks look best when the height is 1.5 to 2 times the width. Many designers follow the “golden rule” which is to make the height equal to 1.6 the width.

Store-bought Plinths

Many lumberyards and millwork companies sell or make plinth blocks that match the profiles of specific door trim molding they sell. This is an easy way to accomplish plinths in your design, as long as your baseboard trim work with the plinth you bought.

In my experience, there are not that many commercially available plinth block sizes available for all the different trim that I deal with.