Siding Overlap and Exposure Calculator

ANA›Life Services Authority›National Calculator Authority›Siding Overlap and Exposure Calculator

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Siding Overlap and Exposure Calculator

Calculate the exposure (face width), overlap, number of courses, and total siding needed for your siding project.

Siding Panel / Board Width (inches)

Overlap / Lap (inches)

Wall Height to Cover (inches)

Wall Width / Length (inches)

Waste Factor (%)

Calculate

function sidCalc() { var resultDiv = document.getElementById('sid-result'); resultDiv.style.display = 'block';

var panelWidth = parseFloat(document.getElementById('sid-panel-width').value); var overlap = parseFloat(document.getElementById('sid-overlap').value); var wallHeight = parseFloat(document.getElementById('sid-wall-height').value); var wallWidth = parseFloat(document.getElementById('sid-wall-width').value); var waste = parseFloat(document.getElementById('sid-waste').value);

// --- Validation --- var errors = []; if (isNaN(panelWidth) || panelWidth 50) errors.push("Waste factor must be between 0% and 50%.");

if (!isNaN(panelWidth) && !isNaN(overlap) && overlap >= panelWidth) { errors.push("Overlap must be less than the panel width."); }

if (errors.length > 0) { resultDiv.innerHTML = 'Please fix the following:' + errors.map(function(e){ return ''; }).join('') + ''; return; }

// --- Core Formulas --- // Exposure = the visible face of each board after overlap var exposure = panelWidth - overlap; // inches

// Number of courses (rows) needed to cover wall height // courses = ceil(wallHeight / exposure) var coursesExact = wallHeight / exposure; var courses = Math.ceil(coursesExact);

// Actual total installed height (may be slightly more than wall height) var totalInstalledHeight = courses * exposure; // inches

// Wall area (sq ft) var wallAreaSqIn = wallHeight * wallWidth; var wallAreaSqFt = wallAreaSqIn / 144;

// Coverage per linear foot of siding (1 board, 1 ft long) = exposure / 12 sq ft var coveragePerLinFt = exposure / 12; // sq ft per lin ft

// Linear feet of siding needed (without waste) // Each course spans the full wall width var linFtNoWaste = (courses * wallWidth) / 12; // lin ft

// With waste factor var wasteMult = 1 + (waste / 100); var linFtWithWaste = linFtNoWaste * wasteMult; // lin ft

// Total siding area (face area installed, with waste) var sidingAreaSqFt = linFtWithWaste * (panelWidth / 12); // sq ft of raw board

// --- Format helpers --- function fmt(n, d) { return n.toFixed(d !== undefined ? d : 2); } function frac(inches) { // Express decimal inches as nearest 1/8" var whole = Math.floor(inches); var dec = inches - whole; var eighths = Math.round(dec * 8); if (eighths === 0) return whole + '"'; if (eighths === 8) return (whole + 1) + '"'; var gcd = function(a,b){ return b ? gcd(b, a%b) : a; }; var g = gcd(eighths, 8); return whole + ' ' + (eighths/g) + '/' + (8/g) + '"'; }

resultDiv.innerHTML = '### Results ' + '' + 'ParameterValue' + 'Exposure (Face Width)' + fmt(exposure, 3) + ' in (' + frac(exposure) + ')' + 'Overlap' + fmt(overlap, 3) + ' in (' + frac(overlap) + ')' + 'Number of Courses' + courses + ' courses' + 'Total Installed Height' + fmt(totalInstalledHeight, 2) + ' in (' + fmt(totalInstalledHeight/12, 3) + ' ft)' + 'Wall Area' + fmt(wallAreaSqFt, 2) + ' sq ft' + 'Linear Feet (no waste)' + fmt(linFtNoWaste, 2) + ' lin ft' + 'Waste Factor' + waste + '%' + 'Linear Feet (with waste)' + fmt(linFtWithWaste, 2) + ' lin ft' + 'Total Siding Board Area (with waste)' + fmt(sidingAreaSqFt, 2) + ' sq ft' + '' + 'Coverage per linear foot of siding: ' + fmt(coveragePerLinFt, 4) + ' sq ft/lin ft

'; }

#### Formulas Used

Exposure = Panel Width − Overlap

Number of Courses = ⌈ Wall Height ÷ Exposure ⌉  (ceiling / round up)

Linear Feet (no waste) = (Courses × Wall Width) ÷ 12

Linear Feet (with waste) = Linear Feet (no waste) × (1 + Waste% ÷ 100)

Total Board Area = Linear Feet (with waste) × (Panel Width ÷ 12)

#### Assumptions & References

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References

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