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Door Header Sizing — Span Tables & Load Bearing

Size headers for door and window openings based on span, loads, and building codes. Supports solid lumber, built-up beams, LVL, glulam, and steel.

Concept Fundamentals
Span / 2
Tributary
(Roof+Floor+Snow) × Trib
Load
1 per 4 ft min
Jack Studs
L/360
Deflection
Size Your HeaderEnter opening width, loads, and header type.

Why This Construction Metric Matters

Why: Undersized headers sag or fail; oversized waste material. Load-bearing walls require proper tributary load calculation and span table selection.

How: Tributary width = span/2. Total load (plf) = (roof + floor + snow) × tributary. Select header from span table where max span ≥ opening and load capacity ≥ total load.

  • ●3 ft opening: 2×8 or 2×10. 6 ft: 2-2×10. 8+ ft: LVL or steel.
  • ●Jack studs: minimum 1 per 4 ft of opening width.
  • ●Non-load bearing: 200 plf minimum design load.
  • ●Verify with local building department; codes vary.
Sources:IRC Span TablesAISC Steel Manual

Door Header Size Calculator

Span tables • Load calculation • Jack studs • Code compliance

Quick Examples — Click to Load

🚪

Standard Interior Door

3 ft opening, non-load bearing

🏠

Exterior Door

3 ft opening, load bearing wall

🚪🚪

Double Door Opening

6 ft opening, moderate load

🚗

Garage Door

8 ft opening, roof load

🪟

Large Window

6 ft opening, second floor

🪟

Sliding Glass Door

8 ft opening, exterior wall

🏢

Two-Story Opening

4 ft opening, floor above

Sample Projects - Click to Load

🚪Easy

Standard Interior Door

3 ft opening, non-load bearing

🏠Medium

Exterior Door

3 ft opening, load bearing wall

🚪🚪Medium

Double Door Opening

6 ft opening, moderate load

🚗Advanced

Garage Door

8 ft opening, roof load

🪟Medium

Large Window

6 ft opening, second floor

🪟Advanced

Sliding Glass Door

8 ft opening, exterior wall

🏢Advanced

Two-Story Opening

4 ft opening, floor above

🔨

Solid Lumber

Single piece dimensional lumber (2x8, 2x10, 2x12)

Max Span: 12 ftStrength: 1xIRC/IRC compliant

📏 Opening Dimensions

Clear opening width of door or window

⚖️ Load Information

Check if wall supports roof or floors above

Planning estimates only. Verify with a licensed engineer or contractor before construction.

📐 Construction Industry Facts

📐

Tributary width = half span on each side.

— IRC

⚖️

Total load (plf) = loads × tributary width.

— Structural

🔨

Jack studs: 1 per 4 ft; king studs: 2 typical.

— IRC

📋

Deflection limit L/360 per building code.

— IBC

What is a Door Header?

A door header (also called a lintel) is a horizontal structural member that spans across the top of a door or window opening. It transfers the load from above (roof, floors, walls) to the vertical supports (jack studs and king studs) on either side. Headers must be properly sized based on the opening width, the loads they carry, and building code requirements to ensure structural integrity and safety.

📏

Span Tables

Header size by span and load

⚖️

Load Calculation

Roof, floor, and snow loads

🔨

Framing Requirements

Jack studs, king studs, cripples

📋

Code Compliance

IRC/IBC building codes

How to Calculate Header Size

Calculation Steps

1. Determine Opening Width: Measure the clear opening width
2. Calculate Loads: Roof load + Floor load + Snow load
3. Find Tributary Width: Half of the span on each side
4. Calculate Total Load: Loads × Tributary width = plf
5. Select Header: Use span table to find size that meets span and load
6. Determine Framing: Calculate jack studs (1 per 4 ft minimum)

Quick Reference

3 ft opening: 2×8 or 2×10 header
6 ft opening: 2×10 or 2-2×10 built-up
8 ft opening: 2-2×12 or LVL required
12+ ft opening: LVL or steel beam

Header Types

Solid Lumber

Single piece dimensional lumber (2x8, 2x10, 2x12)

Max Span:12 ft
Strength:1x
Code:IRC/IRC compliant

Uses: Interior doors, Small windows, Non-load bearing

Built-Up Beam

Multiple pieces nailed together (2-2x8, 2-2x10, etc.)

Max Span:16 ft
Strength:1.8x
Code:IRC compliant

Uses: Wider openings, Moderate loads, Residential

LVL (Laminated Veneer Lumber)

Engineered wood product, stronger than solid lumber

Max Span:24 ft
Strength:2.5x
Code:IBC/IRC approved

Uses: Long spans, Heavy loads, Commercial

Glulam Beam

Glued laminated timber, very strong

Max Span:30 ft
Strength:3x
Code:IBC approved

Uses: Large openings, Heavy loads, Architectural

Steel Beam

Steel I-beam or wide flange

Max Span:40 ft
Strength:5x
Code:IBC/AISC approved

Uses: Very large openings, Maximum loads, Commercial

Span Table Reference

Header TypeHeader SizeMax Span (ft)Load Capacity (plf)Deflection
Solid Lumber2×86200L/360
2×108300L/360
2×1210400L/360
2×1412500L/360
Built-Up Beam2-2×88360L/360
2-2×1010540L/360
2-2×1212720L/360
3-2×1012810L/360
3-2×12141080L/360
LVL (Laminated Veneer Lumber)1.75"×9.25"12500L/360
1.75"×11.25"16750L/360
1.75"×14"201000L/360
3.5"×9.25"141000L/360
3.5"×11.25"181500L/360
Glulam Beam5.125"×9.5"161200L/360
5.125"×11.875"201800L/360
6.75"×13.5"242500L/360
Steel BeamW6×9122000L/360
W8×10163000L/360
W10×12204000L/360
W12×16246000L/360

Framing Components

🔨 Header

Horizontal beam spanning the opening. Transfers loads to vertical supports.

📐 Jack Studs

Vertical supports directly under header ends. Minimum 1 per 4 ft of opening width.

👑 King Studs

Full-height studs on each side. Typically 2 per opening for stability.

📏 Cripple Studs

Short studs above header. Maintain 16" spacing for drywall attachment.

🔧 Trimmers

Double studs for built-up headers. Same count as jack studs.

📊 Bearing Length

Minimum 1.5" bearing on supports. More for heavy loads.

Formulas

Tributary Width = Span / 2
Total Load (plf) = (Roof + Floor + Snow) × Tributary Width
Jack Studs = max(1, Opening Width ft / 4)
Deflection ≤ L/360

FAQs

Load bearing vs non-load bearing? Load bearing walls support roof or floors; use 200 plf minimum for non-load bearing.
When is LVL required? Openings over 8 ft or heavy loads typically need LVL or steel.
Jack stud minimum? 1 per 4 ft of opening width, minimum 1 each side.

Tips

  • • Always verify with local building department; codes vary by jurisdiction
  • • Add 10-15% to load for safety factor on critical openings
  • • Use temporary support during header installation
  • • Ensure adequate bearing length (min 1.5") on jack studs

When to Use This Calculator

Use when sizing headers for new door/window openings, renovations, or verifying existing framing. Essential for load-bearing wall modifications, garage doors, sliding glass doors, and two-story openings.

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⬅️Jump in and explore the concept!
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