Benefits & Uses of a Steel Moment Frame

Steel is common in commercial construction, but did you know it can help strengthen your home, too? Although not frequently used in new home construction, a steel moment frame can be a great way to retrofit or reinforce your home’s structure during a renovation project.

At Lamont Bros. Design & Construction, our team regularly does structural work on homes across the Portland area. Whether it’s for an addition, seismic retrofit, or whole-home remodel, we’ve found that using a steel moment frame can be an effective solution for homes with unique structural needs.

The purpose of this article is to help you understand more about steel moment frames, their uses, and their benefits. When you’re done reading, you’ll understand how a steel moment frame could benefit your home renovation project. The topics we’ll discuss include:

What is a Steel Moment Frame?

A steel moment frame is a structural system used in building construction that consists of vertical columns, horizontal beams, and connections between them that are designed to provide structural support to a building. In its simplest form, it has two vertical columns and a horizontal beam that spans between them.

What Does a Steel Moment Frame Do?

The term “moment frame” refers to the fact that the structure can resist bending moments. These “moments” are caused by horizontal forces acting on the structure.

Moment frames provide two types of structural support. The first is gravity loading, which refers to the weight of a structure. A moment frame supports the weight above it by transferring that weight down through the columns and into the ground. A moment frame can also resist horizontal or lateral forces, such as those caused by wind or earthquakes.

A steel beam can be used to support a second-story addition.

How Much Does a Steel Moment Frame Cost?

The cost to install a steel moment frame into an existing home can vary depending on the circumstances of each project. You can expect to pay anywhere between $50,000-$100,00 for the engineering, fabrication, and installation.

While this may seem like a lot, a foundation replacement or structural retrofit can cost well over $150,000. In comparison, a steel moment frame can end up saving you tens of thousands.

How Can a Steel Moment Frame Benefit Your Remodel?

Depending on the needs of your home renovation project, a steel moment frame can be an effective, cost-friendly solution. Here are a few common applications in remodel construction.

Seismic Retrofits

For areas at high risk of earthquake activity, seismic retrofits are a good way to protect your home from damage or collapse. One common concern in seismic retrofits is when a home has a soft story. This is when a multi-level structure has living space over a large, open lower floor, such as a garage.

If a home has a soft story, a moment frame can help provide the vertical and lateral strength necessary to hold the weight and open up space. The frame reinforces the structure and prevents the upper floor from collapsing into the soft story below.

Large Open Spans

Another use of steel moment frames is for creating large open spans. If you’re planning a remodel and want to remove a load-bearing wall to create a more open floor, a steel moment frame can provide the structural support necessary to open up that span of the wall.

It’s also common to use a moment frame when installing oversize folding exterior doors to create a transitional indoor/outdoor space. These specialty products typically require a large exterior wall opening of 12-20 feet. To ensure that the large door span is properly supported, builders will often use a moment frame around the doorway.

Second Story Additions

In situations where you want to add a second story to a house, a moment frame can make the process much easier. There’s often a lot of retrofitting and structural reinforcement that goes into making sure the home can support the additional weight of a second floor. This may involve strengthening the load-bearing walls as well as upgrading the foundation.

However, when using a steel moment frame, the weight of the second story transfers directly through the frame and into the ground, bypassing the existing structure entirely. This allows you to add a second story on top of the house without having to do as many structural or foundation upgrades.

What is the Installation Process for a Steel Moment Frame?

The process for installing a moment frame in requires careful planning and a good design. The video below by Simpson Strong-Tie shows the basics of installing a steel frame.

Site Preparation

When installing a steel moment frame, the first step is to prepare the site. The location where it will be installed must be cleared of any obstructions and leveled.

Then, the foundation for the frame must be installed. This typically involves excavating the site, placing reinforcement steel, and pouring concrete into the foundation.

Steel Fabrication & Installation

While the site is being prepared, the steel components are fabricated in a fabrication shop according to the specifications of the engineer design and specifications.

The frame is then transported to the site on flatbed trucks or trailers and erected using cranes or other specialized equipment. The columns are first anchored to the foundation. Then the beams and braces are installed using bolts, welding, or a combination of both.

Additional Structure & Finish Work

Once the frame is in place, other structural components such as shear walls and floor systems are installed to complete the structure.

Last, your build team will perform any finish carpentry to complete the space. In most cases, the home’s exterior siding covers the moment frame. Otherwise, your build team may clad the frame in a decorative finish to help it blend into the home’s visual design.

When Should I Use a Steel Moment Frame?

Different home improvement projects have different needs. Here are a few ways to tell if your home might need a steel moment frame.

The Project Involves Gravity or Lateral Loading Above an Existing Structure

A moment frame supports both overhead gravity weight and lateral loads. If the goals of your project involve adding to the gravity or lateral loads acting on your home, a moment frame would be a good choice to ensure stability and strength for both.

Your Foundation is Not Strong Enough to Support Additional Weight

If you’re planning a significant addition but the home’s foundation is not strong enough to support the additional weight, a steel moment frame can help. It allows you to add extra gravity load to the home without first needing to upgrade the home’s foundation or existing structural members.

Your Home’s Design Can Aesthetically Accommodate the Frame

Steel moment frames are a popular choice in modern architectural design since they provide an industrial aesthetic. However, they can also be incorporated into more traditional or even historic homes. The challenge in this case is to embed the frame into the home so it is not visible, or otherwise clad it in a decorative veneer to make it appear less industrial. Designers often use wood veneer to make a steel-moment frame look more like a wooden beam.

Want to Learn More About Structural Remodeling?

Now that you have a better understanding of what a steel moment frame is and how it can benefit your next home improvement project, take the next step in your research. To learn more about foundation repair and the importance of a strong home structure, read our article, “When to Repair the Foundation of a Historic Portland Home.”

Ready to talk to a professional about your home remodeling dreams? Click the link below to schedule a free design consultation with a member of our professional design team. We’ll help you navigate the challenges of remodeling your home so you never have to face the process alone.