Calculating Deck Materials

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Deck Materials Calculator

Planning to build a deck? Use this calculator to estimate the quantities of essential materials you'll need, including decking boards, joists, beams, posts, and concrete for footings. Accurate planning helps you budget effectively and minimize waste.

Decking Board Specifications

Framing Specifications

Post & Footing Specifications

Waste Factor

This calculator provides estimates for common deck configurations. Always consult local building codes and a professional for precise measurements and structural requirements. It's recommended to add an additional waste factor for cuts, errors, and future repairs.

function calculateDeckMaterials() { // Get input values var deckLength = parseFloat(document.getElementById("deckLength").value); var deckWidth = parseFloat(document.getElementById("deckWidth").value); var deckingBoardWidth = parseFloat(document.getElementById("deckingBoardWidth").value); var deckingBoardLength = parseFloat(document.getElementById("deckingBoardLength").value); var joistSpacing = parseFloat(document.getElementById("joistSpacing").value); var joistLength = parseFloat(document.getElementById("joistLength").value); var beamSpacing = parseFloat(document.getElementById("beamSpacing").value); var beamLength = parseFloat(document.getElementById("beamLength").value); var postSpacing = parseFloat(document.getElementById("postSpacing").value); var postHeight = parseFloat(document.getElementById("postHeight").value); var postLength = parseFloat(document.getElementById("postLength").value); var footingDiameter = parseFloat(document.getElementById("footingDiameter").value); var footingDepth = parseFloat(document.getElementById("footingDepth").value); var wasteFactor = parseFloat(document.getElementById("wasteFactor").value); // Validate inputs if (isNaN(deckLength) || isNaN(deckWidth) || isNaN(deckingBoardWidth) || isNaN(deckingBoardLength) || isNaN(joistSpacing) || isNaN(joistLength) || isNaN(beamSpacing) || isNaN(beamLength) || isNaN(postSpacing) || isNaN(postHeight) || isNaN(postLength) || isNaN(footingDiameter) || isNaN(footingDepth) || isNaN(wasteFactor) || deckLength <= 0 || deckWidth <= 0 || deckingBoardWidth <= 0 || deckingBoardLength <= 0 || joistSpacing <= 0 || joistLength <= 0 || beamSpacing <= 0 || beamLength <= 0 || postSpacing <= 0 || postHeight <= 0 || postLength <= 0 || footingDiameter <= 0 || footingDepth <= 0 || wasteFactor < 0) { document.getElementById("deckMaterialsResult").innerHTML = "

Error:

Please enter valid positive numbers for all fields."; return; } var adjustedWasteFactor = 1 + (wasteFactor / 100); // 1. Deck Area var deckArea = deckLength * deckWidth; // 2. Decking Boards // Number of boards needed across the width (convert deck width to inches) var numDeckingBoardsWidth = Math.ceil((deckWidth * 12) / deckingBoardWidth); var totalLinearFeetDecking = numDeckingBoardsWidth * deckLength; var numIndividualDeckingBoards = Math.ceil(totalLinearFeetDecking / deckingBoardLength); // 3. Joists // Number of joists (add 1 for the last joist, convert deck length to inches) var numJoists = Math.ceil((deckLength * 12) / joistSpacing) + 1; var totalLinearFeetJoists = numJoists * deckWidth; var numIndividualJoists = Math.ceil(totalLinearFeetJoists / joistLength); // 4. Beams // Number of beams (add 1 for the last beam, assuming beams run perpendicular to joists) var numBeams = Math.ceil(deckLength / beamSpacing) + 1; var totalLinearFeetBeams = numBeams * deckWidth; var numIndividualBeams = Math.ceil(totalLinearFeetBeams / beamLength); // 5. Posts // Number of posts per beam (add 1 for the last post) var numPostsPerBeam = Math.ceil(deckWidth / postSpacing) + 1; var totalPosts = numBeams * numPostsPerBeam; var totalLinearFeetPosts = totalPosts * postHeight; var numIndividualPosts = Math.ceil(totalLinearFeetPosts / postLength); // 6. Concrete for Footings var footingRadiusFeet = (footingDiameter / 2) / 12; // Convert diameter to radius in feet var footingDepthFeet = footingDepth / 12; // Convert depth to feet var volumePerFootingCubicFeet = Math.PI * Math.pow(footingRadiusFeet, 2) * footingDepthFeet; var totalConcreteVolumeCubicFeet = volumePerFootingCubicFeet * totalPosts; var bags80lbConcrete = Math.ceil(totalConcreteVolumeCubicFeet / 0.6); // Approx 0.6 cubic feet per 80lb bag // 7. Fasteners (Estimates) var deckingScrews = Math.ceil((deckArea / 100) * 350); // Estimate 350 screws per 100 sq ft var joistHangers = numJoists * 2; // One for each end, assuming attached to ledger and beam var postBases = totalPosts; // Apply waste factor to material counts numIndividualDeckingBoards = Math.ceil(numIndividualDeckingBoards * adjustedWasteFactor); totalLinearFeetDecking = (totalLinearFeetDecking * adjustedWasteFactor).toFixed(1); numIndividualJoists = Math.ceil(numIndividualJoists * adjustedWasteFactor); totalLinearFeetJoists = (totalLinearFeetJoists * adjustedWasteFactor).toFixed(1); numIndividualBeams = Math.ceil(numIndividualBeams * adjustedWasteFactor); totalLinearFeetBeams = (totalLinearFeetBeams * adjustedWasteFactor).toFixed(1); numIndividualPosts = Math.ceil(numIndividualPosts * adjustedWasteFactor); totalLinearFeetPosts = (totalLinearFeetPosts * adjustedWasteFactor).toFixed(1); bags80lbConcrete = Math.ceil(bags80lbConcrete * adjustedWasteFactor); deckingScrews = Math.ceil(deckingScrews * adjustedWasteFactor); joistHangers = Math.ceil(joistHangers * adjustedWasteFactor); postBases = Math.ceil(postBases * adjustedWasteFactor); // Display results document.getElementById("resultDeckArea").innerText = deckArea.toFixed(1); document.getElementById("resultDeckingBoards").innerText = numIndividualDeckingBoards; document.getElementById("resultLinearFeetDecking").innerText = totalLinearFeetDecking; document.getElementById("resultJoists").innerText = numIndividualJoists; document.getElementById("resultLinearFeetJoists").innerText = totalLinearFeetJoists; document.getElementById("resultBeams").innerText = numIndividualBeams; document.getElementById("resultLinearFeetBeams").innerText = totalLinearFeetBeams; document.getElementById("resultPosts").innerText = numIndividualPosts; document.getElementById("resultLinearFeetPosts").innerText = totalLinearFeetPosts; document.getElementById("resultConcreteVolume").innerText = totalConcreteVolumeCubicFeet.toFixed(2); document.getElementById("resultConcreteBags").innerText = bags80lbConcrete; document.getElementById("resultDeckingScrews").innerText = deckingScrews; document.getElementById("resultJoistHangers").innerText = joistHangers; document.getElementById("resultPostBases").innerText = postBases; } // Calculate on page load with default values window.onload = calculateDeckMaterials;

Understanding Your Deck Material Needs

Building a deck is a rewarding home improvement project, but it requires careful planning, especially when it comes to material estimation. This calculator helps you get a clear picture of the lumber, concrete, and fasteners you'll need, based on standard construction practices.

Key Deck Components Explained:

• Decking Boards: These are the visible surface boards you walk on. They typically run perpendicular to the joists. Common widths are 3.5 inches (nominal 1×4) or 5.5 inches (nominal 1×6), and lengths vary from 8 to 20 feet.
• Joists: These are the horizontal framing members that support the decking boards. They are usually spaced 12 or 16 inches on center (OC) and transfer the load from the decking to the beams.
• Beams: Larger horizontal members that support the joists. Beams typically run perpendicular to the joists and are supported by posts. Their spacing depends on the joist span and lumber size.
• Posts: Vertical supports that hold up the beams. Posts are usually anchored to concrete footings to prevent settling and provide stability.
• Concrete Footings: These are the concrete bases poured into the ground that support the posts. They distribute the deck's weight over a larger area and prevent frost heave. The diameter and depth are often dictated by local building codes.
• Fasteners: This category includes decking screws (for attaching decking to joists), joist hangers (metal connectors for attaching joists to beams or a ledger board), and post bases (metal connectors for attaching posts to footings).

How the Calculator Works:

The calculator uses your deck's dimensions and your chosen material specifications to estimate quantities. Here's a breakdown of the calculations:

• Deck Area: Simply your deck's length multiplied by its width.
• Decking Boards: The total linear feet of decking is calculated by determining how many boards are needed across the width of the deck and multiplying that by the deck's length. This total linear footage is then divided by your chosen board length to get the number of individual boards.
• Joists: The number of joists is determined by dividing the deck's length (in inches) by your joist spacing (in inches) and adding one for the final joist. This number is then multiplied by the deck's width to get total linear feet, which is then converted to individual joists based on your chosen joist length.
• Beams: Similar to joists, the number of beams is calculated by dividing the deck's length by your beam spacing and adding one. This is then converted to individual beams.
• Posts: The calculator determines how many posts are needed per beam based on your post spacing, then multiplies that by the total number of beams to get the grand total of posts.
• Concrete: The volume of concrete needed for each cylindrical footing is calculated using the formula for the volume of a cylinder (π * radius² * height). This is then multiplied by the total number of posts and converted into the approximate number of 80lb bags of concrete.
• Fasteners: These are rough estimates based on industry averages (e.g., screws per square foot, hangers per joist end).

Considering a Waste Factor:

It's crucial to include a waste factor in your calculations. Lumber can have imperfections, cuts might be mismeasured, or boards might get damaged during transport or installation. A 10-15% waste factor is common and helps ensure you don't run short on materials mid-project, saving you time and extra trips to the lumberyard.

Example Calculation:

Let's say you're building a 16-foot long by 12-foot wide deck:

• Deck Length: 16 feet
• Deck Width: 12 feet
• Decking Board Width: 5.5 inches
• Decking Board Length: 16 feet
• Joist Spacing: 16 inches on center
• Joist Length: 12 feet
• Beam Spacing: 8 feet
• Beam Length: 12 feet
• Post Spacing: 6 feet
• Average Post Height: 4 feet
• Standard Post Length: 8 feet
• Footing Diameter: 10 inches
• Footing Depth: 24 inches
• Waste Factor: 10%

Based on these inputs, the calculator would provide estimates like:

• Deck Area: 192 sq ft
• Decking Boards: Approximately 40 individual 16-foot boards
• Joists: Approximately 26 individual 12-foot joists
• Beams: Approximately 4 individual 12-foot beams
• Posts: Approximately 12 individual 8-foot posts
• 80lb Bags of Concrete: Approximately 20 bags
• Decking Screws: Approximately 739 screws

Remember, these are estimates. Always double-check your local building codes for specific requirements on material sizes, spacing, and footing dimensions.