One of the most essential questions which we all have about trim is, What size should it be? Acquiring the proportions and size of trim correct can make a big difference in the way the room is used and enjoyed. If the trim is too small or too large, it can be just like a clown wearing a minuscule hat or supersize set of shoes.

While there are a few guidelines, they’re, in actuality, just guidelines. No rule should replace what you enjoy and what you believe is perfect. Start out choosing your trim by defining the narrative you and the room want to tell. From there, purchase some samples and have mock-ups built. This is all a small price to pay for receiving your trim right.

Here are the rules — I mean, guidelines — for sizing the trim in a room.

The 7 percent solution. When sizing a baseboard at a traditional-style home, a good starting point would be to use a ratio of 7 percent. If your ceiling height is 8 feet high, try a baseboard that’s about 7 inches tall.

BAAN layout

Obviously, this is more of a suggestion than a rule. For example, if you’re seeking to produce a more contemporary inside, consider using a shorter baseboard or, even if you’re brave enough, no baseboard in any way.

Redbud Custom Homes

For casings, 50 percent is good. Generally, vertical trim elements such as door and window casings should be smaller and have less heft than baseboards. So I’ve found a good guideline for sizing window and door casings would be to maintain them at about 50% of the height of the baseboard.

Winder Gibson Architects

As always, this is not a hard and fast rule. Casings that equal the measurements of the baseboards can work quite well.

Crowning achievements. Even though there are a few guidelines which could be used to size a crown (for example, make it about half of the size of the foundation), there are many questions that come into play, such as:

• How tall is the ceiling?
• Will the crown be convex or concave?
• Will the crown measure out and up of, say, a picture rail?

Given these variables, sizing a crown is not as easy as you might think. I love to purchase foot-long parts of different sizes and profiles and construct mock-ups of the crown within the room. In reality, because most trim is easily available and affordable, this is a excellent process to use for selecting all of your trim elements.

Siemasko + Verbridge

Another principle for crown selection is to use the same crown across the kitchen if your design involves using a crown at the top of your cabinets. Actually, you’re probably going to want the crown to be finished and supplied by the cabinetmaker. Otherwise, the crown will not match, making transitions from one to another problematic.

Alix Bragg Interior Design

All together now. A well-trimmed room is something special. Its baseboard, casings and crown all relate to one another in their style, proportions, sizing and complete. In this example, the baseboard appears to adhere to the 7 percent ruler: The casings are about half of the size of the baseboard, and also the crown seems to be just slightly smaller than the baseboard. There is no doubt that the trim for this particular room was conceived as part of the overall layout.

Shirley Meisels

The rule of thirds. Installing a seat rail, without wainscoting, will split the perpendicular plane — the walls to multiple places. If you want to make the room feel taller, then place the seat rail one third of the way up from the ground.

Mark Brand Architecture

If, on the other hand, you want the room to be more romantic, consider placing the seat rail two thirds of the way up from the ground.

More:
Tell a Home’s Story With Trim
Design Details: Moldings — Or Not?
Frame Your Views With Great Moldings and Casings

See related