When build a building, you need to make sure the doors are correctly supported. The door header is one of the main elements in this process, it distributes the load above the door opening and helps prevent structural failure. But how do you decide if a header size is the right one?

What is a Door Header?

A horizontal structural beam is placed above a door opening to support the weight of the wall or floors above it. The ideal header size really depends on various facets, including:

• Door width (span)
• Load-bearing or non-load-bearing wall type
• A floors above the door
• Type of roof (truss or traditional framing)
• Type of material (Derm, steel, LVL, etc.)

Formula to Calculate Door Header Size

The general formula for header size calculation is:

$H = \frac{L \times S}{F}$ ​

Where:

• H = Required Header Size (in inches)
• L = Load above the door (in pounds)
• S = Span of the door (in inches)
• F = Material Strength Factor

How to calculate header size based on material?

Strength characteristics of different materials differ, hence the need for different header sizes. Here are the formulas for wood and steel headers.

Wood Header Size Calculation

$H_{\text{wood}} = \frac{L \times S}{850}$

Steel Header Size Calculation

$H_{\text{steel}} = \frac{L \times S}{1800}$

Example Calculation

Let’s consider a wooden header for a door with:

• Door Width (Span) = 6 feet
• Load Above Door = 1200 pounds

Step 1: Convert Span to Inches

Since 1 foot = 12 inches:

$S = 6 \times 12 = 72 \text{ inches}$

Step 2: Use the Formula for Wood

Step 2: Use the Formula for Wood

$H_{\text{wood}} = \frac{1200 \times 72}{850}$

$H_{\text{wood}} = \frac{86400}{850}$

$H_{\text{wood}} = 101.65 \text{ inches}$

Thus, the required wooden header size is 101.65 inches.

Conclusion

With the Door Header Size Calculator, calculating header size is simple, and you can ensure that your headers can support the load. To determine the exact size (or sizes) of the headers, it’s best to consult engineering guidelines before proceeding with your construction.