Header Size Calculator

Header requirements depend on whether the wall is load-bearing and how many stories it supports:

Load-Bearing Exterior Walls - Single Story or Roof Only:

Load-Bearing Walls - Supporting 2 Stories:

Non-Bearing Interior Walls:

Built-up headers: (2) means two boards with 1/2" plywood spacer to equal wall thickness

Correctly identifying load-bearing walls is critical—removing support without proper headers causes structural failure:

Load-Bearing Wall Indicators:

• Exterior walls (almost always load-bearing)
• Walls running perpendicular to floor joists/rafters
• Walls directly under beams, other walls, or bearing points
• Walls that stack floor-to-floor through the building
• Walls at the center of the building (mid-span)
• Walls identified as bearing on structural plans

Non-Bearing Wall Indicators:

• Walls running parallel to floor joists
• Walls that don't stack with walls above/below
• Walls labeled "partition" on plans
• Closet walls, bathroom enclosures (usually)
• Walls with no structural elements above

When in Doubt:

What Happens with Undersized Headers:

The Conservative Approach: When uncertain, size headers as if load-bearing. The cost difference between a (2) 2×6 and (2) 2×10 header is $10-30—trivial compared to a $2,000 structural repair.

A proper header assembly includes multiple structural components working together:

King Studs:

• Full-height studs on each side of opening
• Run continuous from bottom plate to top plate
• Provide nailing for door/window jambs
• Transfer vertical loads around opening
• Always required: minimum 1 per side

Jack Studs (Trimmers):

• Shortened studs that directly support header ends
• Nailed face-to-face against king studs
• Transfer header loads down to plate
• Number depends on load and span:

Cripple Studs:

• Short studs above header to top plate
• Maintain regular stud spacing (16" or 24" OC)
• Transfer loads from top plate to header
• Required unless header is at top plate

Sill (Windows Only):

• Horizontal member at bottom of window opening
• Typically (2) 2×4 or single 2×6
• Cripple studs below sill down to bottom plate

Rough Opening Dimensions:

Example: 36" door needs 38.5" rough opening width

Most residential headers are "built-up" from two pieces of dimensional lumber with a plywood spacer:

Standard Built-Up Header Construction (2×4 Walls):

1. Cut two pieces of header lumber to length = Opening + 3" (1.5" bearing each side)
2. Cut 1/2" plywood or OSB spacer strips same dimensions
3. Apply construction adhesive to mating surfaces
4. Sandwich plywood between lumber pieces
5. Nail with 16d nails at 16" OC from both sides, staggered
6. Total width: 1.5" + 0.5" + 1.5" = 3.5" (matches 2×4 wall)

For 2×6 Walls (5.5" thick): Option 1: Double plywood spacer

• 1.5" + 0.5" + 0.5" + 1.5" = 4.0" (add filler strip)

Option 2: Use 4× lumber

• (2) 4×8 with ripped filler = 3" + filler + 3" = ~5.5"

Option 3: 2× lumber + rigid foam

• 1.5" + 2" foam + 1.5" = 5" (insulated header)

Insulated Header Benefits:

Header Assembly Tips:

• Pre-drill near ends to prevent splitting
• Crown lumber and install crown UP
• Ensure bearing surfaces are straight
• Use structural adhesive for added strength

Laminated Veneer Lumber (LVL) and other engineered products provide superior strength for wide spans:

When to Use LVL Headers:

• Openings over 8-10 feet wide
• Supporting heavy loads (multiple stories)
• Limited vertical space (lower header depth)
• Commercial or heavy residential applications
• Where deflection limits are strict

LVL Span Capabilities (single LVL, per 1.75" depth):

Double LVL increases span approximately 40-50%

LVL vs. Dimensional Lumber:

2026 LVL Header Prices:

PSL and Glulam Alternatives:

• PSL (Parallel Strand Lumber): Similar to LVL, available in larger sizes
• Glulam: Best for exposed applications, can be stained
• Steel: For very wide spans or limited height situations

Proper rough opening sizing ensures your door or window fits with appropriate clearance for shimming and adjustment:

Door Rough Opening Formula:

Rough Opening Width = Door Width + 2" (shims) + 0.5" (jamb play)
Rough Opening Height = Door Height + 2" (threshold + shims) + 0.5" (head jamb)

Standard Door Sizes and Rough Openings:

Window Rough Opening: Window RO varies more by manufacturer—always check specifications:

Special Opening Considerations:

Header Length Formula:

Header Length = Rough Opening Width + (Jack Stud Width × 2)
Example: 38.5" RO + (1.5" × 2) = 41.5" header
Practical: Cut to 42" (allows slight adjustment)

Cripple studs maintain load path continuity above headers and below window sills:

Cripple Stud Requirements:

• Must maintain regular stud spacing (16" or 24" OC)
• Align with wall studs when possible
• Transfer loads to header or sill
• Required unless header is at top plate height

Layout Method:

1. Mark regular stud spacing across header top
2. Align first cripple with nearest full stud location
3. Maintain spacing across opening
4. End cripples at king studs (already full height)

Cripple Stud Calculation:

Number of cripples = (Opening width ÷ Spacing) - 1
Example: 48" opening ÷ 16" OC = 3 cripples above header

Cripple Stud Sizing:

Window Framing (Double Cripples): Windows require cripples both above AND below:

When Cripples Aren't Needed:

• Header extends to top plate (no space above)
• Sill sits on bottom plate (no space below)
• Opening fills entire stud bay

2026 Material Costs for Cripples:

Certain conditions require modifications to standard header sizing:

Heavy Snow Load Areas (50+ PSF Ground Snow): Increase header size by one nominal size:

Point Loads Above Opening: When beams, posts, or concentrated loads bear above:

• Consult structural engineer
• May need steel plate or angle
• LVL minimum recommended
• Additional jack studs required

Balloon Framing vs. Platform:

Garage Door Headers: Wide garage doors require special consideration:

Openings Near Corners: Maintain minimum 24" from corner to edge of opening unless:

• Engineering confirms adequate support
• Additional hardware (straps, ties) installed
• Corner post is doubled or tripled

Current pricing for header materials at major suppliers:

Dimensional Lumber Headers (per linear foot):

Complete Built-Up Header Cost (material only):

LVL Header Pricing:

Associated Framing Costs: