Purlin Span Calculator

What is a Purlin Span Calculator?

A Purlin Span Calculator is a tool used to calculate the maximum span or spacing between purlins, which are horizontal beams or members used to support the load of a roof.

It helps ensure that the purlin spacing is appropriate for the roofing material and design to prevent structural issues like sagging or deflection.

Why Use a Purlin Span Calculator?

• Structural Integrity: Calculating the correct purlin span ensures that the roof structure can adequately support the weight of roofing materials, snow loads, and other loads.
• Material Efficiency: It helps optimize the use of purlins by determining the minimum number required for a given roof design.
• Cost Efficiency: Proper purlin spacing can result in cost savings by reducing the amount of material needed for the project.

How to Use a Purlin Span Calculator:

1. Input the width of the roof (in feet), which is the horizontal distance from one edge of the roof to the other.
2. Input the roof slope (in inches of rise per foot of run), which represents the angle of the roof.
3. Enter the desired purlin spacing (in feet), which is the distance between adjacent purlins.
4. Click the "Calculate" button.
5. The calculator will provide the maximum recommended purlin span (in feet) based on the input parameters.

Example Calculation:

Let's say you have the following parameters:

• Roof Width (W): 24 feet
• Roof Slope (S): 4 inches of rise per foot of run
• Desired Purlin Spacing (D): 4 feet

Using these values in the provided HTML code:

• Roof Slope (in radians) ≈ atan(4/12) ≈ 0.321 radians
• Purlin Span ≈ 24 feet / (tan(0.321 radians) * 4 feet) ≈ 31.07 feet

So, the maximum recommended purlin span is approximately 31.07 feet for the given roof width, slope, and desired purlin spacing.

This calculation helps ensure the structural integrity of the roof.

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