Enter Header Details
Example Data Table
These sample values help compare common exterior opening cases.
| Opening type | Span | Tributary condition | Common starting section | Review focus |
|---|---|---|---|---|
| Small window | 3 ft | Roof only | 2 plies × 1.5 in × 5.5 in | Bearing and local code |
| Patio door | 6 ft | Roof plus wall | 2 plies × 1.5 in × 9.25 in | Deflection and flashing |
| Wide slider | 8 ft | Roof plus floor | 2 plies × 1.75 in × 11.875 in | Bending and reactions |
| Garage opening | 12 ft | Multiple loads | Engineered member | Professional design |
Formula Used
The calculator treats the header as a simply supported beam. Uniform load is assembled from tributary roof load, floor load, wall load, and cladding load.
- Uniform line load: w = roof tributary width × roof psf + floor tributary width × floor psf + wall plf + cladding plf.
- End reactions: RA = wL ÷ 2 + P(L − a) ÷ L. RB = wL ÷ 2 + Pa ÷ L.
- Moment scan: M(x) = RAx − wx² ÷ 2 − P(x − a), when x is beyond the point load.
- Section properties: S = bd² ÷ 6. I = bd³ ÷ 12.
- Bending stress: fb = M ÷ S. Shear stress is estimated as fv = 1.5V ÷ bd.
- Deflection: service-load deflection is sampled using elastic beam formulas for uniform and point loads.
- Bearing: required bearing length = maximum reaction ÷ (Fc⊥ × header width).
Final structural sizing must follow local code, approved plans, and manufacturer design data.
How To Use This Calculator
- Enter the clear span of the exterior opening.
- Add the header build-up, material preset, and adjustment factors.
- Enter roof, floor, wall, cladding, and point load details.
- Choose the deflection limit that fits your project need.
- Press the calculate button and review each demand ratio.
- Increase depth, width, bearing, or material strength if any ratio exceeds 1.000.
Header Guide
Exterior Header Planning Basics
An exterior load bearing header carries weight above an opening. That opening may hold a window, door, slider, or garage jamb. The header collects roof, floor, wall, and point loads. It then sends those loads into jack studs and foundation supports. Good sizing protects finishes, doors, cladding, and structural connections.
Loads To Review
A header is usually checked as a simply supported beam. The clear opening is the beam span. The tributary width tells how much roof or floor area feeds the header. Dead load includes framing, sheathing, siding, drywall, and fixed finishes. Live load covers use, storage, and temporary occupancy. Snow load can govern roof headers in cold regions. A concentrated load may come from a girder, post, truss, or upper beam.
Strength And Service Checks
The calculator estimates uniform load in pounds per foot. It also adds an optional point load. It calculates end reactions, bending moment, shear, deflection, and bearing demand. Bending checks compare stress with adjusted allowable bending value. Shear checks compare vertical shear stress with allowable shear value. Deflection checks compare beam movement with the selected span limit. Bearing checks compare reaction pressure with the bearing length entered.
Material Selection
Built-up sawn lumber, laminated veneer lumber, and engineered members can act very differently. Stronger material may allow less depth. More plies add width and section capacity. Greater depth usually improves bending strength and stiffness faster than extra width. Still, connections between plies must transfer load. Nailing, screws, bolts, and manufacturer rules matter.
Practical Framing Notes
Exterior headers also need good moisture control. Flashing should move water away from the opening. King studs and jack studs must align with the load path below. Cripple studs should be tight and properly fastened. Long openings may need deeper members or engineered review. Wall bracing and uplift ties can also affect the final detail.
Document each assumption before comparing sizes. Keep units consistent during entry. Small load changes can move a design from passing to failing. The safest choice is usually verified with drawings and field conditions before site work begins.
Use the output as a planning guide. It is not a permit approval. Local codes, load paths, and product data control final sizing. Ask a licensed professional to review important structural changes.
FAQs
What is an exterior load bearing header?
It is a structural beam above an exterior wall opening. It carries roof, floor, wall, and sometimes point loads. It transfers those loads to jack studs or posts at each side of the opening.
Can this calculator replace an engineer?
No. It gives preliminary sizing checks only. Final design can require local code review, product tables, lateral bracing checks, connection design, and field inspection by a qualified professional.
What span should I enter?
Enter the clear opening distance between supports. Do not include the bearing length unless your design documents define span differently. Accurate span entry is critical for bending and deflection checks.
What is tributary width?
Tributary width is the loaded width of roof or floor area feeding the header. It is often half the distance to the next parallel support on each side, but framing layout controls the real value.
Why does depth matter so much?
Depth strongly improves section modulus and moment of inertia. That means deeper headers usually gain bending strength and stiffness quickly. Width also helps, but depth often controls longer spans.
What does a demand ratio above 1 mean?
A ratio above 1.000 means the entered member fails that check. Increase depth, width, material strength, bearing length, or reduce load. Then rerun the calculation and review all checks again.
How are point loads handled?
The calculator places the point load at the entered distance from the left support. It adds the point load to reactions, bending, shear, and service deflection checks using simply supported beam behavior.
Should snow and roof live load both be entered?
Enter the loads required by your design basis. Some jurisdictions use governing combinations rather than adding every temporary load directly. Local code rules and engineering judgment should control final load selection.
What bearing length is acceptable?
Minimum bearing depends on reaction, material bearing strength, wall framing, and code requirements. The calculator estimates required bearing from reaction pressure, but local minimums may still govern.
Can I use engineered lumber values?
Yes. Choose a preset or enter custom values from the product report. Use the manufacturer values for bending, shear, stiffness, bearing, fastening, and any required adjustment factors.
Why is deflection checked separately?
A header can be strong enough but still bend too much. Excess movement can crack finishes, bind doors, damage windows, or affect cladding. Serviceability checks help reduce those problems.