One of the most crucial components of designing a frame to install a window is the window header—specifically, the window header size.
Not only is it important to size the header to the opening correctly for a smooth window installation, but it’s also important for the structural integrity of your home. If your header is too small, your window may not open or close properly, and the frame or glass may shatter. A structural failure of a portion of your home is the worst-case scenario.
What Is a Window Header, and Why Do I Need One?
Any strong beam that spans a horizontal opening, such as a doorway, is referred to as a header. A window header is a piece of artwork that spans the top of a window opening. The header, like a bridge, is the structural structure that allows the space below to be open rather than closed.
Consider a window header. Normally, there would be a wood-frame external wall in that location. Studs placed every 16 or 24 inches would create a vertical force-bearing wall structure. The window header allows you to remove some studs while keeping the wall’s structural integrity.
Sizes of Typical Window Headers
Window headers are normally made up of two pieces of dimensional sawn lumber stacked on top of each other. The depth of the wall limits the thickness of window headers, as it does other elements used in wall systems.
Two-by-fours, which are 3-1/2 inches wide, are used in most wall systems. The use of thicker beams can increase the strength of the structure. However, this is not possible in walls since they must always retain a 3-1/2-inch depth. As a result, the solution is to move up: use broader pieces of lumber that extend vertically higher.
3 ft. window span
Use two two-by-fours or one four-by-four for windows spanning 36 inches or less. This is a common window header size since many windows are in the 24-inch to 34-inch width range.
Span of the window: 4 feet, 6 inches
Increase the side of the window header to two-by-sixes for 4 feet, 6 inches or less for window spans. Because many windows are in the 45- to 50-inch range, this window span is commonly employed.
Window Span: 5 feet, 9 Inches
Use two two-by-eight pieces of lumber for even wider window spans of 5 feet, 9 inches or less.
Factors Affecting Header Dimensions
These window header size suggestions are for a single-story residence with a 20-foot width. The length of the window header span is reduced as buildings become wider. Window header sizes can also be affected by heavy snow or other circumstances. That’s why it’s critical to adhere to local building codes during construction.
To be safe, some do-it-yourselfers and builders will over-build the window header. Several two-by-twelves side-by-side are usually employed for 6-foot patio or french doors and 4-foot wide window openings.
Overbuilding will only add a small amount to the expense. One disadvantage is that it causes more heat bridging between the inside and outside. In this crucial location, less insulation is being used.
Quantities of King and Jack Studs
Two king studs and two jack studs are required for each window header (one on each side). However, four jack studs (and two king studs) may be needed if window sizes widen. Adding another story to a building reduces window widths and increases the chance of extra jack studs being required.
Window Headers Made of Laminated Veneer Lumber (LVL)
For window headers, laminated veneer lumber, or LVL, can be used instead of sawn lumber.
To make larger beams, laminated veneer lumber uses thin veneer layers. The layers are glued together in the manufacturing and held under great pressure until they are joined. Glulam beams are another type of LVL: full-sized lumber bonded under great pressure to produce beams.
LVL outperforms standard sawn dimensional timber in terms of strength and stiffness. The value of LVL can be seen in very large spans, such as garage door heads or french doors. Because of the increased price of LVL, it’s best to utilize it for window header spans of 6 feet rather than smaller windows that can be easily bridged with other materials.
Need Professional Help?
If you believe it may be better to replace your window completely and need help, contact Moldings Plus at (909) 947-3310 to schedule a showroom consultation today!
