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Calculate structural ridge beam size, load capacity, and deflection. Determine required beam dimensions for your roof structure with support reactions and alternative sizing options.
Total width of the building (ridge supports half on each side)
Distance between ridge posts or supports
Weight of roof structure (shingles, decking, etc.)
Regional snow load (check local building code)
Wind, construction, maintenance load
Total width: 11.25" × 11.25" deep
Enter ridge span to calculate capacity
Your load: 0 lbs/ft
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| Feature | Ridge Beam (Structural) | Ridge Board (Non-Structural) |
|---|---|---|
| Function | Carries roof load to posts | Connects rafters at peak |
| Size Required | Engineered, varies by load | Usually 1" nominal (½" actual) |
| Rafter Bearing | Sits on top, full bearing | Cut into rafter ends (tenon) |
| Ceiling Joists | Not required (if roof framed properly) | Required to prevent outward thrust |
| Post Support | Posts/columns required at ends | No posts needed (or minimal) |
| Cathedral Ceiling | Allows cathedral ceilings | Restricts cathedral designs |
| Cost | Higher (engineering, posts) | Lower cost, simpler |
| Code Approval | Requires calculation/plan | Standard construction |
Ridge beam posts must be spaced based on beam capacity. Typical guidelines:
Light roofs (double 2x8):
12-16 feet O.C.
Medium roofs (double 2x10-12):
16-24 feet O.C.
Heavy roofs (LVL/Glulam):
20-32+ feet O.C.
Minimum 3.5" for wood posts, 4" for masonry
Use structural post caps for uplift resistance
Install adequate bracing to prevent rotation
A ridge beam is a structural member that carries the roof load and transfers it to posts, while a ridge board is non-structural and only connects the rafter pairs. Ridge beams are sized by calculation; ridge boards are standard 1-inch lumber. Ridge beams eliminate the need for ceiling joists.
Yes, a structural ridge beam is ideal for cathedral ceilings. It carries the roof load directly to posts, eliminating the need for ceiling joists that would block the ceiling view. A ridge board cannot support a cathedral ceiling without additional structural support.
You need a structural ridge beam if: (1) you want a cathedral ceiling, (2) ceiling joists would be visually undesirable, (3) your roof spans are large, or (4) local building codes require one. If you have continuous ceiling joists meeting the ridge, a ridge board typically suffices.
Steeper roof pitches increase the effective load on the ridge beam due to the slope multiplier (based on rise and run). A 12:12 roof (45 degrees) has a 1.41x multiplier, meaning loads are 41% higher than horizontal projection. Steeper pitches require larger beams.
The ridge beam receives loads from rafters on both sides. The tributary area for the ridge is typically one-half the building width (the distance from the ridge to the wall on each side). This area multiplied by the roof load (psf) gives the load per linear foot on the ridge beam.
Ridge beams typically have a L/180 deflection limit (more stringent than floor beams at L/360) to minimize visible sagging and prevent rafters from slipping. Some codes may allow L/240 depending on conditions and valley framing considerations.
Yes, steel beams can work for ridges and allow extremely long spans. However, they require adequate bearing plates, proper support (columns/posts), thermal bridging consideration for insulation, and are typically more expensive than engineered wood beams like LVL or glulam for residential applications.
For custom residential projects with cathedral ceilings or larger spans, a structural engineer is recommended. This calculator provides estimates, but professional design ensures code compliance, proper support calculations, and builder confidence. Local codes may require engineer approval.
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