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Ridge Beam Tributary Load Calculator

Calculate the load per linear meter carried by a structural ridge beam supporting cathedral-ceiling rafters.

Computed in your browser — nothing you enter is uploaded. Figures are presented for United States against IRC 2024, and every formula is cited under regulatory standards below.

Last verified 2026-08-26 · v1.0.0

Market
Imperial · sales tax
26.25 ft
Schematic, drawn to the proportions you entered — not to scale on screen.

Ridge beam load per linear meter

8 kN/m

Check your inputs

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.

With the figures above, the ridge beam load per linear meter comes to 8 kN/m. The method behind this is well established, though site conditions and material batches will move it somewhat. This is calculated for United States and cites IRC 2024. Building in another market? Change the selector above so the units and code reference follow.

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This result is a specification — 8 kN/m — not a quantity. Put the thing it sizes into your project: how many, what you call it, and your supplier’s price.

Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — confirmed fixes become pinned regression tests.

[Schema Verified] Computed in alignment with American Concrete Institute (ACI 318-19) formulas and International Residential Code (IRC 2024) spatial boundaries.

Regulatory standards & verification citations

  • 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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Frequently asked questions

Why does a structural ridge beam carry load from the full building width?
Without ceiling rafter ties to resist outward thrust, each rafter behaves as a simply-supported beam spanning between the wall and the ridge — the ridge beam ends up carrying half the tributary load from each of the two roof slopes, which together sum to half the full building width's roof load.
Does this apply to a standard ridge board as well?
No — a conventional ridge board is not a structural beam; it relies on rafter ties (or a ceiling diaphragm) to resist thrust and does not carry this kind of tributary gravity load. This calculator applies specifically to a structural ridge beam in a cathedral-ceiling or open-ridge design.
What load path assumption does this calculator make?
It assumes simply-supported rafters bearing directly on the ridge beam with no intermediate supports or rafter ties — irregular framing, dormers, or valleys will change the actual tributary area and should be checked separately by a structural engineer.