1. What is Tributary Area?

The tributary area is the area of floor or roof that contributes load to a structural member (like a beam or column). For deck beams, it's calculated as half the joist span multiplied by the beam spacing.

2. How Does the Calculator Work?

The calculator uses the tributary area formula:

Where:

• Joist Span — Distance between supporting beams (feet)
• Beam Spacing — Distance between parallel beams (feet)

Explanation: The formula accounts for the load distribution from decking to joists to beams.

3. Importance of Tributary Area Calculation

Details: Calculating tributary area is essential for determining structural loads on beams and columns, ensuring proper sizing of structural members for safety and code compliance.

4. Using the Calculator

Tips: Enter joist span and beam spacing in feet. Both values must be positive numbers. The calculator will determine the tributary area in square feet.

5. Frequently Asked Questions (FAQ)

Q1: Why divide joist span by 2?
A: The load from each joist is distributed equally to the two beams supporting it, so each beam carries half the span's load.

Q2: How does this relate to total load?
A: Multiply tributary area by load per square foot (e.g., 50 psf for residential decks) to get total load on the beam.

Q3: What about cantilevered sections?
A: Cantilevers require different calculations as the load distribution changes.

Q4: Does this work for roof structures?
A: Yes, the same principle applies to roof framing members.

Q5: Should I include safety factors?
A: This calculator provides basic tributary area. Always consult building codes and a structural engineer for final designs.