What Are Cutting Edge’s Mullion Frame Specs?

Discover Cutting Edge’s standard mullion frame specs, including bar widths, styles, patterns, and customization options to avoid problems.

A kitchen featuring a combination of Hickory and white painted cabinet doors, with mullion frames. A mullion frame is a traditional accent item.
Image provided by Warman Homes; kitchen designed and installed by Warman Cabinets, customer

When ordering a mullion frame, you want confidence in what you’re getting. But let’s face it – standard specifications can vary greatly between suppliers. This can leave contractors and cabinet makers like you frustrated. How can you ensure the mullion frame matches your design or existing cabinetry? What are the dimensions, styles, and patterns available? Can you customize these specifications without delays or additional costs?

At Cutting Edge, we know your challenges. With over 20 years of expertise and an established network of reliable processes, we’ve built a reputation for delivering consistent, high-quality mullion frames. Each year, we produce over 200 mullion frames, ensuring precision in every design. 

This article breaks down our standard mullion frame specs, so you know exactly what to expect. You will learn:

The Components of a Mullion Frame

A mullion frame is a decorative type of glass cabinet door. The main difference between glass cabinet doors and mullion frames is the presence of mullion bars. Mullion frames have mullion bars that divide the opening into multiple, smaller openings.

There are two types of mullion frames:

Traditional mullion frames feature mullion bars that are flush with the exterior frame of the door. These bars are typically straight, creating clean and symmetrical designs that lend themselves to a timeless and classic look. This style is ideal for projects requiring simplicity and elegance.

An infographic showing how a traditional mullion frame is assembled.

Mullion insert frames, on the other hand, offer a more intricate and detailed appearance. The inserts are placed between the glass and the back profile of the frame, creating a layered effect. This design adds an extra dimension of refinement, making it perfect for projects that demand a touch of sophistication.

An infographic showing how a mullion insert frame is assembled.

Regardless of the mullion frame style you order from Cutting Edge, you will only need to install a single pane of glass.

Cutting Edge’s Standard Specifications for Each Part of a Mullion Frame

Each part of a mullion frame is customizable – but if you don’t request a specific customization, you will receive the standard dimension. But what are those standards? And how customizable is each part?

Let’s start with the foundation; the exterior frame.

The Standard Specifications for the Exterior Frame

The exterior frame supports the entire structure of a mullion frame, whether a traditional or mullion insert option. There are two aspects to the frame:

  1. The width, often referred to as the stile and rail width, sets the width for each piece of the exterior frame. At Cutting Edge, the standard stile and rail width is 2.25 inches unless you choose a mitred profile with a default width.
  2. The thickness refers to how deep the frame is from front to back. Most of Cutting Edge’s profiles are ¾ inch thick. Like the width, mitred profiles may have a default thickness.

Can You Customize the Exterior Frame?

You can customize the width of the stiles and rails to some extent.  While increasing the width is possible, reducing it below 2.25 inches is not recommended. Narrower widths may compromise stability, leaving insufficient space for glass inserts and hinge drilling. 

However, if you opt for a mitred profile, you must choose from its predefined widths.

The Standard Specifications for Mullion Bars

Mullion bars are essential to the structure and design of traditional mullion frames, dividing the opening into multiple sections. There are two aspects to mullion bars:

  1. The width of the mullion bars depends on the inside profile of the stiles and rails. This ensures the bars remain flush with the face of the frame and the glass, creating a seamless appearance. Cutting Edge offers the following standard widths based on the selected profile:
      • 0.875 inches for Profiles 4, 4R, 5, 7, and 9.
      • 1.375 inches for Profiles 8 and 8-Mod.
      • 2.125 inches for Profiles 23 and 23-Mod.
      • 1.125 inches for all other profiles.
  2. The thickness of the mullion bars matches the depth of the inside profile. A deeper profile requires thicker bars to maintain alignment and ensure durability.

Can You Customize the Mullion Bar Width?

While you can request wider mullion bars for specific designs, narrower widths are not an option. This restriction ensures the safety of our employees and maintains the structural integrity of the frame during manufacturing and installation.

A white mullion frame with a red line showing the mullion bar width. The width of the mullion bars depends on the profile you select for your mullion frames.

The Standard Specifications for Mullion Inserts

Mullion inserts add a decorative and functional layer to the frame by fitting between the glass and the back profile. These inserts offer greater customization. There are two aspects to mullion inserts:

  1. Thickness. Cutting Edge’s mullion inserts are 4 mm thick, allowing them and a piece of glass to fit snugly into the frame. However, this is not enough thickness to allow for a profile that matches the frame, so mullion inserts aren’t profiled.
  2. Design. Unlike mullion bars, mullion inserts can have curved bars. As default, the details in Cutting Edge’s mullion inserts are 0.5 inches wide – narrower than any mullion bars.

Can You Customize Mullion Inserts?

Yes, customization is possible. While Cutting Edge offers four standard insert patterns, you can request custom designs to suit unique project requirements. This flexibility allows you to achieve a look that aligns with your vision.

The Seven Standard Mullion Frame Patterns

You can choose from a variety of traditional mullion frame patterns. As a rule of thumb, each opening should be around 4 inches wide and high to prevent a cluttered feel.

  • M2 mullion frames have a single bar that divides the frame into two equal openings. You can choose either a horizontal or vertical orientation.
  • M3 mullion frames have two mullion bars that divide the frame into three equal openings. This option defaults to a vertical orientation, meaning the openings are stacked one on top of the next.
  • M4 mullion frames have a cross pattern with two mullion bars splitting the frame into four equal sections.
  • M6 mullion frames have three mullion bars that split the frame into six equal sections. This option also defaults to a vertical orientation, meaning each pair of openings is stacked on top of the next pair.
  • M8 mullion frames have four mullion bars that produce 8 equal openings. This option also defaults to a vertical orientation, meaning each pair of openings is stacked on top of the next pair.
  • M9 mullion frames, also known as prairie mullions, have four mullion bars that split the frame into nine openings. The four corner openings have fixed dimensions – 2 inches square. The dimensions of the other five openings change as the exterior frame dimensions change.
  • MX mullion frames have two mullion bars, meeting in an X pattern. 

You can also adjust the mullion bar spacing, orientation, and location to customize your mullion frames.

An M9 or prairie mullion frame. These are one of the rarest mullion frames thanks to their unique appearance.

At Cutting Edge, horizontal mullion bars continue across the full width of the frame, while vertical mullion bars are split up into multiple pieces.

4 Standard Mullion Insert Patterns for Mullion Frames

For a detailed look, Cutting Edge provides four standard mullion insert patterns. These intricate designs add a unique touch to your cabinetry. While we recommend choosing from these patterns, custom options are always available to meet your vision.

When you order wood mullion insert frames, the mullion inserts have vertical grain.

Four standard styles of custom mullion frames. You can choose from these insert patterns when ordering a mullion frame from Cutting Edge, or create a custom option.

2-Piece MDF Mullion Frames Break the Rules

MDF is the exception to the standard rules that apply to mullion frames. At Cutting Edge, we offer 2-piece MDF mullion frames that provide unique flexibility while maintaining the same high-quality craftsmanship.

With MDF mullion frames, you have two distinct options:

  • Profiled and Curved Mullion Bars: Unlike traditional mullion frames, 2-piece MDF allows for intricate profiles and curves in the mullion bars. These bars remain flush with the face of the frame, ensuring a sleek, cohesive appearance while giving you more creative freedom in your design.
  • Mullion Inserts: You can pair 2-piece MDF frames with MDF mullion inserts. These inserts fit seamlessly between the glass and the back profile, just like their counterparts in other materials.

This flexibility makes 2-piece MDF mullion frames an excellent choice for painted projects requiring custom designs or unique patterns while maintaining structural integrity. Whether you opt for profiled bars or mullion inserts, MDF mullion frames provide the perfect balance of style and practicality.

A white painted 2-piece MDF mullion frame with curved and profiled mullion bars. 2-piece MDF mullion frames are the exception to most mullion frame rules.

Price Out Your Mullion Frame Online

In the past, ordering mullion frames often meant navigating unclear specifications and inconsistent results. Standard specifications vary from supplier to supplier, leading to confusion and inconsistencies. Today, Cutting Edge empowers you with reliable standards and flexible customization options, helping you deliver impeccable results for your clients.

Now that you understand our mullion frame specifications, it’s time to take the next step. Learn how to price out mullion frames online. 

Your Next Step To Working With Cutting Edge Download your guide to working with Cutting Edge for information about ordering, contractor accounts, pricing, lumber grades, and more.