Trusses Calculator

Truss Geometry Calculator

Calculation Results:

Calculated Rise: 0.00 feet

Top Chord Length (per side): 0.00 feet

Total Top Chord Material: 0.00 feet

Bottom Chord Length: 0.00 feet

Roof Pitch (degrees): 0.00 °

Individual Top Chord Panel Length: 0.00 feet

function calculateTrussGeometry() { var trussSpan = parseFloat(document.getElementById('trussSpan').value); var pitchX = parseFloat(document.getElementById('pitchX').value); var overhangLength = parseFloat(document.getElementById('overhangLength').value); var numTopChordPanels = parseInt(document.getElementById('numTopChordPanels').value); // Validate inputs if (isNaN(trussSpan) || trussSpan <= 0) { alert("Please enter a valid positive number for Truss Span."); return; } if (isNaN(pitchX) || pitchX <= 0) { alert("Please enter a valid positive number for Roof Pitch (X)."); return; } if (isNaN(overhangLength) || overhangLength < 0) { alert("Please enter a valid non-negative number for Overhang Length."); return; } if (isNaN(numTopChordPanels) || numTopChordPanels <= 0) { alert("Please enter a valid positive integer for Number of Top Chord Panels."); return; } var pitchRun = 12; // Standard for X/12 pitch // Calculate Rise var calculatedRise = (trussSpan / 2) * (pitchX / pitchRun); // Calculate Top Chord Length (per side) var topChordLengthSide = Math.sqrt(Math.pow(trussSpan / 2, 2) + Math.pow(calculatedRise, 2)); // Calculate Total Top Chord Material (both sides) var totalTopChordMaterial = 2 * topChordLengthSide; // Calculate Bottom Chord Length var bottomChordLength = trussSpan + (2 * overhangLength); // Calculate Roof Pitch in Degrees var roofPitchDegrees = Math.atan(calculatedRise / (trussSpan / 2)) * (180 / Math.PI); // Calculate Individual Top Chord Panel Length var individualPanelLength = topChordLengthSide / numTopChordPanels; // Display results document.getElementById('calculatedRise').innerText = calculatedRise.toFixed(2); document.getElementById('topChordLengthSide').innerText = topChordLengthSide.toFixed(2); document.getElementById('totalTopChordMaterial').innerText = totalTopChordMaterial.toFixed(2); document.getElementById('bottomChordLength').innerText = bottomChordLength.toFixed(2); document.getElementById('roofPitchDegrees').innerText = roofPitchDegrees.toFixed(2); document.getElementById('individualPanelLength').innerText = individualPanelLength.toFixed(2); }

Understanding Trusses and Their Geometry

Trusses are fundamental structural components widely used in construction, particularly for roofs, bridges, and large spans. They consist of a framework of interconnected members, typically forming triangular units. The triangular shape is inherently stable, making trusses incredibly efficient at distributing loads and resisting deformation.

Why Use Trusses?

• Strength-to-Weight Ratio: Trusses can span long distances with less material than solid beams, making them lighter and more economical.
• Load Distribution: They effectively transfer loads to supporting walls or columns, minimizing stress on individual members.
• Versatility: Available in various configurations (e.g., King Post, Queen Post, Fink, Howe, Pratt) to suit different architectural and structural requirements.
• Open Spaces: The open web design allows for easy routing of plumbing, electrical, and HVAC systems.

Key Geometric Parameters Explained

Accurate measurement and calculation of truss geometry are crucial for structural integrity and material estimation. Our calculator helps you determine these key dimensions:

• Truss Span: This is the horizontal distance covered by the truss, typically measured from the outside edge of one supporting wall to the outside edge of the other. It's the clear distance the truss needs to bridge.
• Roof Pitch (X in X/12): Roof pitch describes the steepness of a roof. It's expressed as a ratio, where 'X' is the vertical rise for every 12 units of horizontal run. For example, a 6/12 pitch means the roof rises 6 inches for every 12 inches of horizontal distance. This is a critical factor in determining the overall height and aesthetic of your roof.
• Overhang Length: The overhang is the portion of the truss that extends horizontally beyond the supporting wall. Overhangs provide protection for walls and foundations from rain and sun, and contribute to the building's architectural style.
• Number of Top Chord Panels (per side): The top chord of a truss is divided into segments by the web members. The number of panels per side influences the length of each individual segment, which is important for cutting and assembly.

Understanding the Calculator's Outputs

Based on your inputs, the calculator provides essential dimensions:

• Calculated Rise: This is the total vertical height from the bottom chord (at the center of the span) to the peak of the top chord.
• Top Chord Length (per side): The actual length of one sloped top chord member, from the support point to the peak. This is crucial for ordering lumber or steel.
• Total Top Chord Material: The combined length of both top chord members, giving you an estimate for the total material needed for the main sloped elements.
• Bottom Chord Length: The total horizontal length of the bottom member of the truss, including any overhangs.
• Roof Pitch (degrees): The angle of the roof slope expressed in degrees, which can be useful for various design and construction tasks.
• Individual Top Chord Panel Length: The length of each segment along the top chord on one side of the truss. This helps in precise cutting of web members and panel sheathing.

Example Calculation:

Let's say you have a truss with:

• Truss Span: 24 feet
• Roof Pitch (X/12): 6/12 (so X = 6)
• Overhang Length: 1 foot
• Number of Top Chord Panels (per side): 4

Using the calculator:

• Calculated Rise: (24 / 2) * (6 / 12) = 12 * 0.5 = 6 feet
• Top Chord Length (per side): √((12²) + (6²)) = √(144 + 36) = √180 &approx; 13.42 feet
• Total Top Chord Material: 2 * 13.42 = 26.84 feet
• Bottom Chord Length: 24 + (2 * 1) = 26 feet
• Roof Pitch (degrees): atan(6 / 12) * (180 / π) &approx; 26.57°
• Individual Top Chord Panel Length: 13.42 / 4 &approx; 3.36 feet

Disclaimer: This calculator provides geometric estimations for planning purposes. For actual construction, always consult with a qualified structural engineer or truss manufacturer to ensure compliance with local building codes and structural requirements.