Roof Truss Calculator

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Roof Truss Calculator

Calculation Results:

Ridge Height: 0.00 feet

Sloped Rafter Length (per side, with overhang): 0.00 feet

Total Roof Surface Area: 0.00 sq ft

Number of Trusses Required: 0

Estimated Total Lumber (Chords Only): 0.00 linear feet

Estimated Material Cost (Chords Only): $0.00

Estimated Labor Cost: $0.00

Total Estimated Project Cost: $0.00

Note: Lumber estimate is for top and bottom chords only. It does not include internal webbing, gusset plates, or waste factor. Always consult with a structural engineer for precise designs and material lists.

function calculateRoofTruss() { var buildingSpan = parseFloat(document.getElementById('buildingSpan').value); var buildingLength = parseFloat(document.getElementById('buildingLength').value); var roofPitchDegrees = parseFloat(document.getElementById('roofPitchDegrees').value); var overhangHorizontal = parseFloat(document.getElementById('overhangHorizontal').value); var trussSpacing = parseFloat(document.getElementById('trussSpacing').value); var lumberCostPerFoot = parseFloat(document.getElementById('lumberCostPerFoot').value); var laborCostPerTruss = parseFloat(document.getElementById('laborCostPerTruss').value); // Input validation if (isNaN(buildingSpan) || buildingSpan <= 0 || isNaN(buildingLength) || buildingLength <= 0 || isNaN(roofPitchDegrees) || roofPitchDegrees = 90 || isNaN(overhangHorizontal) || overhangHorizontal < 0 || isNaN(trussSpacing) || trussSpacing <= 0 || isNaN(lumberCostPerFoot) || lumberCostPerFoot < 0 || isNaN(laborCostPerTruss) || laborCostPerTruss < 0) { alert('Please enter valid positive numbers for all fields. Roof pitch must be between 0 and 90 degrees.'); return; } // Convert pitch to radians var pitchRadians = roofPitchDegrees * (Math.PI / 180); // 1. Ridge Height var ridgeHeight = (buildingSpan / 2) * Math.tan(pitchRadians); // 2. Sloped Rafter Length (without overhang) var rafterLengthSloped_no_overhang = (buildingSpan / 2) / Math.cos(pitchRadians); // 3. Sloped Overhang Length var overhangSloped = overhangHorizontal / Math.cos(pitchRadians); // 4. Total Sloped Rafter Length (with overhang) var rafterLengthSloped_with_overhang = rafterLengthSloped_no_overhang + overhangSloped; // 5. Total Roof Surface Area (both sides) var totalRoofArea = 2 * rafterLengthSloped_with_overhang * buildingLength; // 6. Number of Trusses Required // Add 1 for the first truss, then calculate for the rest of the length var numTrusses = Math.ceil(buildingLength / trussSpacing) + 1; // 7. Estimated Total Lumber (Top and Bottom Chords only per truss) // Two top chords (rafters) + one bottom chord (span) var totalChordLengthPerTruss = (2 * rafterLengthSloped_with_overhang) + buildingSpan; var totalLumberLinearFeet = totalChordLengthPerTruss * numTrusses; // 8. Estimated Material Cost (Chords Only) var estimatedMaterialCost = totalLumberLinearFeet * lumberCostPerFoot; // 9. Estimated Labor Cost var estimatedLaborCost = numTrusses * laborCostPerTruss; // 10. Total Estimated Project Cost var totalEstimatedCost = estimatedMaterialCost + estimatedLaborCost; // Display results document.getElementById('ridgeHeight').innerText = ridgeHeight.toFixed(2); document.getElementById('rafterLengthSloped').innerText = rafterLengthSloped_with_overhang.toFixed(2); document.getElementById('totalRoofArea').innerText = totalRoofArea.toFixed(2); document.getElementById('numTrusses').innerText = Math.round(numTrusses); // Display as whole number document.getElementById('totalLumberLinearFeet').innerText = totalLumberLinearFeet.toFixed(2); document.getElementById('estimatedMaterialCost').innerText = estimatedMaterialCost.toFixed(2); document.getElementById('estimatedLaborCost').innerText = estimatedLaborCost.toFixed(2); document.getElementById('totalEstimatedCost').innerText = totalEstimatedCost.toFixed(2); } // Run calculation on page load with default values window.onload = calculateRoofTruss;

Understanding Roof Trusses and Their Importance

Roof trusses are engineered structural components that form the framework of a roof, supporting its weight and transferring loads to the building's walls. Unlike traditional stick-built roofs that use individual rafters, ceiling joists, and collar ties assembled on-site, trusses are prefabricated in a factory setting. This prefabrication offers numerous advantages, including consistency, speed of installation, and often, cost-effectiveness.

Key Components of a Roof Truss:

  • Top Chords: These are the upper members of the truss, forming the slope of the roof. They support the roof decking and roofing materials.
  • Bottom Chord: The horizontal member at the base of the truss, often serving as the ceiling joist for the space below.
  • Web Members: The internal diagonal and vertical pieces that connect the top and bottom chords, forming a series of triangles. These webs are crucial for distributing forces and providing rigidity.
  • Gusset Plates: Metal plates, typically galvanized steel, used to connect the chords and web members at their joints, ensuring structural integrity.

Benefits of Using Roof Trusses:

  1. Cost-Effective: Trusses often use less lumber than stick-built roofs and their factory production minimizes waste.
  2. Faster Installation: Being pre-assembled, trusses can be installed much quicker on-site, reducing labor costs and project timelines.
  3. Consistent Quality: Manufactured under controlled conditions, trusses offer uniform quality and precise dimensions.
  4. Design Flexibility: Trusses can be engineered to accommodate a wide range of roof designs, spans, and load requirements.
  5. Open Spans: They can span long distances without intermediate supports, allowing for more open floor plans below.

How to Use the Roof Truss Calculator:

Our Roof Truss Calculator provides an estimate for key dimensions and costs associated with your roof truss project. Here's a breakdown of the inputs:

  • Building Span: The total horizontal width of your building that the trusses will cover, from outside wall to outside wall.
  • Building Length: The total length of your building along the ridge line.
  • Roof Pitch (degrees): The angle of your roof's slope, measured in degrees. A common pitch is 30 degrees.
  • Horizontal Overhang: How far the roof extends horizontally beyond the exterior wall. This protects walls and foundations from rain.
  • Truss Spacing: The distance between the center of each individual truss. Common spacings are 16 inches (1.33 feet) or 24 inches (2 feet).
  • Lumber Cost per Linear Foot: An estimated cost for the lumber used in the main chords of the trusses. This can vary significantly based on wood type, grade, and market conditions.
  • Labor Cost per Truss: An estimated cost for the fabrication and/or installation of a single truss. This will depend on your location and whether you're buying pre-fabricated trusses or having them built on-site.

Understanding the Results:

  • Ridge Height: The vertical distance from the top of the wall plate to the peak (ridge) of the roof.
  • Sloped Rafter Length (per side, with overhang): The actual length of one top chord, from the wall plate to the ridge, including the sloped portion of the overhang.
  • Total Roof Surface Area: The total square footage of your roof's surface, useful for estimating roofing materials like shingles or metal panels.
  • Number of Trusses Required: The total count of trusses needed for your building length, based on your specified spacing.
  • Estimated Total Lumber (Chords Only): A rough estimate of the total linear feet of lumber required for the top and bottom chords across all trusses. Note: This does not include the internal web members or any waste factor.
  • Estimated Material Cost (Chords Only): The calculated cost for the estimated lumber length.
  • Estimated Labor Cost: The total estimated cost for fabricating and/or installing all the trusses.
  • Total Estimated Project Cost: The sum of the estimated material and labor costs.

This calculator provides a helpful preliminary estimate for planning purposes. For precise structural design, material lists, and accurate costings, always consult with a qualified structural engineer, truss manufacturer, or building contractor.

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