Door Header Size Calculator

Structural Load Analysis

Calculate the required size for door headers to support structural loads. Essential for construction professionals, builders, and structural engineers to ensure proper beam sizing and load capacity.

Examples

Click on any example to load it into the calculator.

Residential Interior Door

Residential Interior Door

Standard interior door in a residential building with typical floor loads.

Door Width: 0.9 m

Load per m²: 2.4 kN/m²

Material: Wood

Safety Factor: 1.5

Header Length: 1.2 m

Exterior Door with Heavy Load

Exterior Door with Heavy Load

Exterior door supporting a second floor with higher loads.

Door Width: 1.2 m

Load per m²: 4.8 kN/m²

Material: Steel

Safety Factor: 1.8

Header Length: 1.5 m

Garage Door Header

Garage Door Header

Large garage door opening requiring substantial structural support.

Door Width: 3.6 m

Load per m²: 3.6 kN/m²

Material: Concrete

Safety Factor: 2.0

Header Length: 4.0 m

Commercial Building Door

Commercial Building Door

Commercial building entrance with high traffic and load requirements.

Door Width: 1.8 m

Load per m²: 6.0 kN/m²

Material: Steel

Safety Factor: 1.6

Header Length: 2.2 m

Other Titles
Understanding Door Header Size Calculation: A Comprehensive Guide
Explore the fundamental principles of structural engineering, load analysis, and beam design for door openings in construction projects.

What is a Door Header?

  • Structural Purpose
  • Load Transfer Mechanism
  • Design Considerations
A door header is a horizontal structural element that spans across a door opening to support the load from the structure above. It transfers the weight of the wall, floor, and roof loads around the opening to the adjacent wall sections or columns.
Structural Function
When a door opening is created in a load-bearing wall, the header must carry the loads that would normally be supported by the wall section that was removed. This includes dead loads (the weight of the structure itself) and live loads (occupancy, furniture, etc.).
Load Distribution
The header acts as a beam that spans the door opening and transfers the loads to the wall sections on either side. The size of the header must be sufficient to resist bending moments and shear forces without exceeding the material's allowable stresses.

Key Concepts:

  • Headers must support all loads above the opening
  • Size depends on span, load, and material properties
  • Safety factors ensure structural reliability

Step-by-Step Guide to Using the Door Header Size Calculator

  • Understanding Your Inputs
  • Choosing the Right Parameters
  • Interpreting the Results
This calculator helps you determine the required size for door headers based on structural engineering principles. Follow these steps to get accurate results for your specific application.
1. Measure Door Opening
Start by measuring the width of the door opening. This is the clear span that the header must bridge. Common residential door widths range from 0.8 to 1.2 meters, while commercial doors can be 1.5 to 2.4 meters or more.
2. Determine Load Requirements
Calculate the total load per square meter that the header must support. This includes the weight of the floor or roof above, plus any live loads. Typical residential loads are 2.4-3.6 kN/m², while commercial loads can be 4.8-7.2 kN/m².
3. Select Material and Safety Factor
Choose the header material based on your project requirements. Wood headers are common in residential construction, while steel and concrete are used in commercial and industrial applications. The safety factor accounts for uncertainties in load estimation and material properties.
4. Analyze Results
Review the calculated header size and stress values. Ensure that the bending and shear stresses are within acceptable limits for the chosen material. The header size should provide adequate strength while being practical to construct.

Design Tips:

  • Always consult local building codes
  • Consider deflection limits for serviceability
  • Account for construction tolerances

Real-World Applications of Door Header Design

  • Residential Construction
  • Commercial Buildings
  • Industrial Applications
Door header design is critical in various construction scenarios, from simple residential renovations to complex commercial and industrial projects. Understanding the principles helps ensure structural integrity and safety.
Residential Applications
In residential construction, headers are commonly used for interior and exterior doors, garage doors, and window openings. Wood headers are popular due to their ease of installation and cost-effectiveness. Typical residential headers range from 2x6 to 2x12 lumber or engineered wood products.
Commercial and Industrial Uses
Commercial buildings often require larger openings and higher load capacities. Steel headers are commonly used for their strength and durability. Concrete headers provide excellent fire resistance and are used in high-rise buildings and industrial facilities.
Special Considerations
Special applications include fire-rated doors, security doors, and doors in seismic zones. These may require additional reinforcement or specific material requirements to meet code and performance standards.

Common Applications:

  • Interior and exterior doors
  • Garage and overhead doors
  • Commercial building entrances

Common Misconceptions and Correct Methods

  • Size vs. Strength
  • Load Distribution
  • Material Selection
Several misconceptions exist about door header design that can lead to structural problems. Understanding these helps ensure proper design and construction.
Bigger is Not Always Better
A common misconception is that larger headers are always stronger. While size affects strength, the relationship is not linear. Proper design considers the specific load requirements and material properties rather than simply using the largest available member.
Load Distribution Myths
Some believe that loads are distributed evenly across the header. In reality, the load distribution depends on the structural system above the opening. Point loads, concentrated loads, and varying floor loads all affect the actual loading pattern.
Material Selection Errors
Choosing materials based solely on availability or cost can lead to problems. Each material has specific properties, and the design must account for factors like moisture resistance, fire rating, and long-term durability.

Design Principles:

  • Match material properties to load requirements
  • Consider environmental factors
  • Account for construction methods

Mathematical Derivation and Examples

  • Beam Theory Fundamentals
  • Moment and Shear Calculations
  • Stress Analysis
The mathematical analysis of door headers is based on fundamental beam theory and structural mechanics principles. Understanding these calculations helps verify design adequacy.
Beam Analysis Fundamentals
A door header acts as a simply supported beam with a uniformly distributed load. The maximum moment occurs at the center of the span and is calculated as M = wL²/8, where w is the load per unit length and L is the span length.
Shear Force Analysis
The maximum shear force occurs at the supports and is calculated as V = wL/2. This shear force must be resisted by the header material and connections. For most materials, shear stress is calculated as τ = 3V/2A, where A is the cross-sectional area.
Stress Calculations
Bending stress is calculated as σ = M/S, where S is the section modulus. The section modulus depends on the cross-sectional shape and dimensions. For rectangular sections, S = bh²/6, where b is the width and h is the height.
Design Verification
The calculated stresses must be compared to the allowable stresses for the material, divided by the safety factor. If the actual stress exceeds the allowable stress, the header size must be increased or a stronger material selected.

Calculation Example:

  • For a 1.2m door with 3.6 kN/m² load
  • Moment = 3.6 × 1.2² / 8 = 0.648 kN·m
  • Shear = 3.6 × 1.2 / 2 = 2.16 kN