What Is Window Header Framing and How Does It Work?

Whether remodeling, adding on or building “from scratch,” building strong, stable walls is a priority of any construction project. Then, opening after opening is cut into these walls to accommodate windows, entry doors and patio doors we love. Strange, yes. But if these openings are created correctly, we never have to fear our walls or houses will collapse. And that “right way” means using the structural support system that has been developed over the years to keep houses solid and happy.

Ahead, find pro-tips and advice about how to frame a window from contractor Gerda Swedowsky and Randall Roberts from Window Works.

What Are Window Headers?

Window headers are beams that provide structural support across open spans in window framing. They allow openings for windows without weakening a wall.

What’s a Door Header?

A door header is the same as a window header but bridges the gap in wall framing for a door opening.

Headers for Large Openings

The longer the distance a header spans and the heavier the load it supports, the more substantial it needs to be. Undersized headers will bow downward, pinching windows and doors and making them difficult to operate.

Headers for large openings are constructed with engineered wood products that are designed to span longer distances and carry greater loads.

How Do Headers Work?

Headers take the weight of the materials and occupants above and transfer it via the trim studs down to the floors and foundations below.

In most wood-frame dwellings, headers are thick beams constructed of dimensional lumber installed on the edge. These headers are supported on each end by vertical pillars (normally composed of 2x4s or 2x6s) called king studs and jack studs.

The king studs nailed into the end of each header and the jack studs that butt just under the header on each end combine to create a sturdy support column.

Together, the headers, king studs and jack studs act as a system that transfers weight from above, down and around the window and door openings to the floor and foundation.

Longer headers and those supporting more weight may require additional jack studs. “The number is determined by the width of the opening and amount of weight above it,” Roberts says. “It’s usually one or two on each side.”

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Parts of a Header

Most headers are built of two pieces of dimensional lumber and a spacer board for added width to match the surrounding framing. These three boards are then “nailed together in a regular pattern so that they are essentially one piece of wood,” Swedowsky says. The spacer is often plywood or rigid foam board.

Do you need headers on non-load-bearing walls?

“You do not need headers on non-load bearing walls,” Swedowsky says. On a non-load-bearing wall, a single 2×4 laid flat across the top of the window opening is sufficient. “Although, it is nice to double that 2×4, so that you have solid nailing for your trim,” Swedowsky says.

How Do Window and Door Headers Differ?

“There is really no difference between a window header and a door header,” Swedowsky says. However, window headers work in conjunction with sills and cripple studs, which door headers do not.

Sills establish the bottoms of window rough openings (the clear opening required for installing windows and doors). Cripple studs support the space between the window sill and the bottom nailing plate.

Cripple studs are sometimes added above a window or door header to fill the gap between the header and top nailing plate.

What Size Window Header Do You Need?

Calculating header size is complicated, but determined DIYers can use the International Residential Code, which provides tables and charts. “One can enter the data based on the application and find the proper sized header using dimensional lumber,” Roberts says.

You have to take into account:

• The length of the window or door opening;
• The combined weight of the floors, walls and roofs above;
• The building width;
• The snow load in the area;
• Whether it’s a load-bearing wall;
• Whether it’s an exterior or interior bearing wall; and
• What species of wood you’re working with

How to Determine Header Sizing

Instead of wading into all the technicalities, my advice is this when building a header to frame a window:

1. Have an engineer or architect calculate the required header size for your window and door openings and follow their plans.

2. Build a double 2×12 header sandwich, as we explain next. In all but the most bizarre situations, they’ll easily carry the weight for 4-foot wide window and door openings and, in most situations, be code-compliant for openings up to 6 feet wide—a common patio door width. Its finished thickness is also flush with the existing 2×4-inch framing.

How To Build Window Headers and Door Headers

• Measure and cut two 2×12-in. boards to the length of the opening between the king studs.
• Measure and cut 1/2-in. plywood or rigid foam to the same size as the 2x12s.
• Sandwich the three boards, with the plywood in the center, and nail them together with 3 1/4-in. framing nails.

About the Experts

• Gerda Swedowsky is a licensed contractor with over thirty years of industry experience. She has worked in framing, cabinetry and home remodeling.
• Randall Roberts is the owner of Window Works in Hadley, Massachusetts, a sales, installation and service company specializing in windows, doors and siding. He has been a licensed contractor for over 30 years.