Wickfords Timber · Structural Tool

Ridge Beam Sizing Calculator

Calculate the required size of a ridge beam to support rafters based on roof loading, material selection, and support configuration.

Structure Dimensions

Enter the building and roof dimensions.

Ridge Length m

Structure Width m

Roof Pitch degrees

Rafter Spacing m

Rafter Overhang m

Ridge Overhang m

Material Selection

Select the beam material and grade.

Beam Material

Grade

Roof Covering

Beam Support Configuration

How is the ridge beam supported?

Support Type

Beam Size

–

Bending Stress

–

Deflection

–

Bending Stress–

Shear Stress–

Max Moment–

Max Shear–

Bearing Area Required–

Modulus of Elasticity–

How this calculator works

1. Load Calculation

The total load on the ridge beam is calculated from:

Dead Load: Weight of the roof covering and structure
Live Load: Snow, maintenance, and other temporary loads
Wind Load: Wind pressure on the roof

Total Load = Dead Load + Live Load + Wind Load

2. Beam Analysis

The maximum bending moment and shear force are calculated based on the support configuration:

2 Points: Simply supported beam
3 Points: Continuous beam with one intermediate support
4 Points: Continuous beam with two intermediate supports

3. Section Sizing

The required section modulus is calculated from the bending moment and material strength:

S_required = M × 10⁶ / (fm × 0.9)

Where fm is the bending strength of the material and 0.9 is a safety factor.

4. Verification

The calculator checks:

Bending: Actual stress < Allowable stress
Shear: Actual stress < Allowable shear stress
Deflection: Actual deflection < L/240 limit
Bearing: Adequate bearing area for the load

5. Rafter Sizing

The calculator suggests appropriate rafter sizes based on:

SA Pine CCA Treated: Standard structural timber sizes
I-Joists: Engineered timber I-joists in standard sizes
Selection based on span, spacing, and roof load

This tool gives an indicative ridge beam size based on the values you enter. It does not account for all load combinations, local building codes, or connection design. Always have the final structural design reviewed by a qualified engineer before construction.