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The combined dead and live load carried by the roof, per unit of horizontal roof area.
Per unit of HORIZONTAL area in plan, not of sloping roof surface — snow and live loads are defined on the plan projection, and using the slope area double-counts the pitch the tributary width already accounts for. Dead load is genuinely per slope area and is usually converted to plan for this reason. Where the roof carries a ceiling below, that load is part of this too if the ridge beam picks it up.
The full width of the building, measured eave to eave across both roof slopes.
A structural ridge beam supporting cathedral-ceiling rafters (no horizontal ceiling ties) picks up half the tributary load from each roof slope, so its load depends on the full building width, not just one slope's run.
Ridge beam load per linear meter
543 lbf/ft
Assumes simply-supported rafters bearing directly on a structural ridge beam with no rafter ties — verify actual load path with a structural engineer for irregular framing.
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Ridge Beam Tributary Load Calculator: 543 lbf/ft — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
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How this was calculated
Formula source(s)
- For a structural ridge beam supporting simply-supported rafters (no ceiling rafter ties), each rafter transfers half its tributary load to the ridge; summed across both roof sides, ridge load per unit length = roof load × building width ÷ 2
Inputs used
- Total Roof Load, Dead+Live
- 41.77 psf
- Building Width
- 26 ft
Confidence note: Assumes simply-supported rafters bearing directly on a structural ridge beam with no rafter ties — verify actual load path with a structural engineer for irregular framing.
What this calculation does not cover
- Produces a load, not a beam. The section comes from applying that load over the clear span between supports and checking it three ways — bending, shear at the bearings, and a deflection limit tight enough that the ridge does not sag visibly over a cathedral ceiling — and doubling the span roughly quadruples the bending demand at the same load per unit length.
- Stops at the underside of the beam. All the load on it lands on the posts at its ends, and those posts have to run continuously down through the floors to a footing sized for that point load. A ridge beam bearing on a wall top plate with ordinary studs and no post beneath it is the common failure, and it shows as a dip in the floor below long before the roof complains.
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This result is a specification — 543 lbf/ft — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.
Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-09-06 · in the site-wide review of 2026-09-06 · v1.1.1
Regulatory standards & verification citations1
- For a structural ridge beam supporting simply-supported rafters (no ceiling rafter ties), each rafter transfers half its tributary load to the ridge; summed across both roof sides, ridge load per unit length = roof load × building width ÷ 2
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