Deck Cost Calculator
Estimate total deck building cost including materials and labor
Deck Cost Calculator
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How to Use This Calculator
Start by selecting your deck size using the dropdown or entering custom dimensions. Common deck sizes are 10×12 (120 sq ft), 12×16 (192 sq ft), 12×20 (240 sq ft), and 16×20 (320 sq ft). Larger decks require more support posts and beams. The calculator uses your dimensions to determine all structural requirements: joists, beams, posts, and footings. For multi-level or complex deck shapes, calculate each level/section separately and sum the materials.
Choose your decking material: pressure-treated lumber (most economical, $15-25 per sq ft total project), cedar ($25-35 per sq ft), composite ($30-45 per sq ft), or PVC/plastic ($35-55 per sq ft). Pressure-treated pine requires annual maintenance (cleaning and staining) but costs least up-front. Composite and PVC require no staining but cost 2-3× more initially—they save money long-term through avoided maintenance. Each material has different joist spacing requirements: PT and cedar use 16-inch centers, some composites require 12-inch centers (more joists needed), affecting cost.
Select railing style: none (for low deck), wood ($20-40 per linear foot), composite ($40-80 per linear foot), metal ($60-120 per linear foot), or glass panels ($150-300 per linear foot). Building codes require railings on decks higher than 30 inches above grade. Measure perimeter needing railing—typically three sides of deck, with the fourth side against the house. A 12×20 deck needs 44 feet of railing (12+20+12). At $50 per linear foot for composite railing, that's $2,200 just for railings—a significant cost component.
Input your location to estimate permit and labor costs. Building permits for decks cost $100-500 depending on deck size and jurisdiction. Some areas require professional drawings ($300-800) for decks larger than 200 sq ft or higher than 30 inches. Professional installation labor ranges from $15-35 per sq ft depending on complexity and location. A 12×20 (240 sq ft) deck with moderate complexity costs $3,600-8,400 in labor. The calculator provides total project cost including materials, labor, permits, and accessories (stairs, lighting, fasteners). Results help you decide DIY versus professional installation—DIY saves 40-60% but takes 3-5× longer.
Understanding Deck Cost Calculations
Deck structural requirements follow strict building codes for safety and longevity. The foundation consists of concrete footings (below frost line depth to prevent heaving) supporting posts, which support beams, which support joists, which support decking. Footing depth varies by climate: 12 inches in frost-free zones, 42-48 inches in cold climates. Each footing typically requires one 50-pound bag of concrete ($5-8). Post spacing depends on beam size: 2×8 beams span 8 feet, 2×10 beams span 10 feet, 2×12 beams span 12 feet. Joist spacing is typically 16 inches on center for wood decking, 12 inches for some composites. Understanding this hierarchy helps estimate materials accurately.
Decking material choice affects initial cost, maintenance, longevity, and total cost of ownership. Pressure-treated pine costs least up-front ($2-4 per linear foot for boards) but requires annual maintenance (cleaning $100-200, staining/sealing $1-2 per sq ft) and replacement every 15-20 years. Cedar costs more initially ($5-8 per linear foot) but resists rot naturally and lasts 20-25 years with minimal maintenance. Composite costs $4-10 per linear foot, requires no staining, lasts 25-30 years, but fades in direct sunlight. PVC/plastic costs $6-12 per linear foot, never needs staining, lasts 30-50 years, and won't fade or stain. Calculate 20-year cost of ownership: PT deck costs less year 1 but accumulates $2,000-4,000 in maintenance; composite costs more initially but saves long-term.
Joist sizing and spacing follow span tables based on wood species and spacing. For pressure-treated Southern Yellow Pine (most common), 2×6 joists span 9 feet at 16-inch centers, 2×8 span 12 feet, 2×10 span 15 feet, 2×12 span 18 feet. Using larger joists reduces the number needed but costs more per piece. A 12-foot wide deck using 2×8 joists at 16-inch centers needs 10 joists (144 inches ÷ 16 = 9 joists + 1 = 10). Using 2×10s costs 30% more per joist but might allow eliminating a beam, saving overall. Always consult local span tables—they vary by wood species, grade, and local snow loads.
Attachment to the house requires a ledger board (pressure-treated 2× lumber) securely fastened to the house rim joist with lag screws or through-bolts. This connection bears significant load and is the most common failure point in deck collapses. Ledger must attach to solid framing (rim joist or studs), not just siding or sheathing. Required fasteners: 1/2-inch lag screws or through-bolts every 16 inches, washers required. Flashing above the ledger prevents water intrusion that rots the house band board. Improper ledger attachment causes deck collapse—hire a professional if unsure. Many jurisdictions require engineer-stamped drawings for ledger attachments on older homes.
Stairs and railings are often underestimated in cost but represent 20-30% of total deck budget. Code-compliant stairs require 7.75-inch maximum rise, 10-inch minimum tread depth, continuous handrail, and balusters spaced no more than 4 inches apart (prevents child head entrapment). A 36-inch high deck needs 4-5 steps costing $200-500 in materials plus $300-800 in labor. Railing codes require 36-42 inch height (42 inches is safer for children), balusters every 4 inches maximum, and railing capable of withstanding 200-pound horizontal force. Railing materials range from pressure-treated wood ($20-40 per linear foot) to composite ($40-80), metal ($60-120), or glass panels ($150-300). For a 12×20 deck needing 44 linear feet of railing, costs range from $880 to $13,200 based on material choice.
Formula & Calculations
Calculate total decking square footage, then convert to linear feet of boards. For a 12×20 deck: 12 × 20 = 240 sq ft. Standard deck boards are 5.5 inches actual width (6-inch nominal). To cover 12 feet (144 inches) width: 144 ÷ 5.5 = 26.2 boards, round to 27 boards. Each board is 20 feet long (matching deck length), so you need 27 pieces of 5.5×20-foot boards. If using 12-foot boards, you need two per row: 27 × 2 = 54 pieces of 12-foot boards. Add 10% waste for cuts and defects: 54 × 1.10 = 59.4, round to 60 boards. At $12 per 12-foot board, decking material = 60 × $12 = $720.
Calculate joists based on spacing and deck dimension. For our 12×20 deck with joists running 20-foot length at 16-inch spacing: deck width 12 feet = 144 inches. Number of joists = 144 ÷ 16 = 9 spaces + 1 starting joist = 10 joists. Each joist is 20 feet long, so 10 pieces of 2×8×20-foot lumber. At $22 per 20-foot 2×8, joists = 10 × $22 = $220. Add blocking (cross-bracing between joists): 10 spaces × 12 feet per space ÷ 8 feet per 2×8 blocking = 15 pieces of 8-foot 2×8 at $12 each = $180 for blocking.
Calculate beams and posts. Beams support joists and span between posts. For our 12×20 deck, one beam runs the 20-foot length, sitting on 4 posts (one at each end and two in middle, spacing posts 6-7 feet apart for 2×10 beam strength). Beam requires two 2×10×20-foot boards sandwiched together (built-up beam), or one 4×10 beam. Using built-up: 2 × $35 per 20-foot 2×10 = $70 for beam. Posts are 6×6 pressure-treated, height varies by deck elevation. For 24-inch high deck, use 8-foot posts cut to size: 4 posts × $32 each = $128. Add post bases ($15 each × 4 = $60) and beam hangers/hardware ($80-120).
Calculate footings: one per post. Four posts = four footings. Each footing requires one 80-pound bag of concrete in frost-free zones, or two bags in cold climates for 12-inch diameter × 42-inch deep footings. Eight bags × $6 = $48 for concrete. Add cardboard tube forms ($8-15 each × 4 = $60). Total structural cost: $720 decking + $220 joists + $180 blocking + $70 beam + $128 posts + $60 post bases + $100 hardware + $48 concrete + $60 forms = $1,586 materials for structure and decking. Add railing (44 linear feet × $50 = $2,200), stairs ($400), fasteners ($150), permits ($300), labor if hiring ($3,600-8,400 for 240 sq ft × $15-35) = Total project cost $6,236-12,636 for completed 240 sq ft deck.
Key Factors to Consider
Ground slope and elevation dramatically affect project cost and complexity. A flat yard allows a simple low deck (12-18 inches high) with minimal posts and no stairs, costing $15-25 per sq ft total. Sloped yards require elevated decks with multiple post levels, long posts, extensive footings, and tall stairs, costing $25-45 per sq ft. A deck elevated 6-8 feet above grade requires 10-12 foot posts ($40-60 each versus $25-35 for short posts), extensive bracing, and possibly multiple stair landings with intermediate platforms. Always verify existing grade before estimating—many homeowners discover significant slope requiring expensive solutions.
Frost depth requirements affect footing costs significantly. Frost-free climates (southern US) allow 12-inch deep footings using one 50-80 pound concrete bag per footing. Cold climates require footings below frost line: 42 inches in moderate cold zones, 48-60 inches in very cold zones. Deep footings need 2-3 bags of concrete each and cardboard tube forms ($10-15 each). A 12-post deck in frost-free zone: $60-90 for concrete. Same deck in cold climate: $180-270 for concrete plus $150-180 for forms. Pier blocks (precast concrete) work in frost-free zones at $15-25 each, saving labor but only code-compliant in warm climates.
Composite decking variations affect joist spacing and costs. Standard composites (Trex, TimberTech, Fiberon) require joists at 16-inch centers like wood decking. Some hollow-core composites require 12-inch centers for adequate support, increasing joist count by 33% and structural costs by $200-500 for typical deck. Verify manufacturer specifications before planning framing. Composite boards also cost $4-10 per linear foot versus $2-4 for pressure-treated lumber—material cost for decking alone can double or triple. However, composite avoids annual $300-500 staining costs and lasts 25-30 years versus 15-20 for pressure-treated. Factor total cost of ownership over expected deck lifespan.
Building codes and permits vary dramatically by jurisdiction and deck size/height. Many areas allow permit-free decks under 200 sq ft and under 30 inches high. Larger or higher decks require permits ($100-500), professional plans ($300-800), and inspections ($0-200). Some jurisdictions require engineer-stamped drawings for any deck, adding $500-1,500. Coastal and high-wind zones have enhanced fastening requirements. Decks in Homeowners Associations may need architectural approval (weeks or months of delay). Always check requirements before starting—building without required permits risks fines ($500-5,000) and forced removal.
Access and site conditions affect labor costs and DIY feasibility. Easy access allows lumber delivery near build site, minimizing material handling. Difficult access (fenced backyard, no gate wide enough for lumber delivery, steep slopes) requires hand-carrying all materials hundreds of feet, increasing labor costs 20-40% or making DIY impractical. Delivery fees also increase for difficult access ($100-300 surcharge). Underground utilities (gas, electric, water, sewer) require locating before digging footings—call 811 for free locate service 2-3 days before digging. Hitting utilities causes expensive repairs ($1,000-10,000+) and possible service disruption to neighborhood. Tree roots, ledge rock, or high water table complicate footing excavation, potentially requiring specialized equipment or engineered solutions (helical piers, elevated beams).
Frequently Asked Questions
1How much does it cost to build a 12x20 deck?
A 12×20 deck (240 sq ft) costs $3,600-10,800 total depending on materials and labor. DIY with pressure-treated lumber: $2,500-4,000 materials (decking, framing, concrete, fasteners, basic wood railing). Hiring professionals with PT lumber: $5,000-7,500 ($20-30 per sq ft). Composite decking DIY: $4,500-7,000. Composite professional install: $8,000-12,000 ($30-45 per sq ft). Premium materials (IPE, PVC, glass railing): $12,000-18,000 professional. Cost factors: ground slope (flat cheaper than steep), railing style (wood $1,000 vs glass $7,000 for 44 linear feet), stairs (add $500-1,500), location (permits, labor rates), and deck height (elevated costs more). Most homeowners spend $6,000-8,000 for professionally built PT deck with composite railing.
2Is it cheaper to build a deck or patio?
Concrete patios cost less than decks in most situations: $6-15 per sq ft for basic concrete versus $15-35 per sq ft for decks. A 12×20 (240 sq ft) concrete patio costs $1,500-3,500, while equivalent deck costs $3,600-8,400. However, ground slope changes economics—decks work on sloped yards where patios require expensive excavation and fill. On a 4-foot slope, deck costs $5,000-8,000 versus patio needing $3,000-5,000 in grading/retaining walls plus $2,500 concrete = $5,500-7,500 total (similar cost). Aesthetics matter: decks provide elevated views and integrate with home exit doors. Patios are more durable (concrete lasts 30-50 years versus deck 15-30 years) but less attractive and don't add to home exit points.
3How long does it take to build a deck?
Professional crews build typical 12×20 decks (240 sq ft) in 3-5 days: Day 1 - layout, footing holes, pour concrete. Day 2 - set posts, install beams and joists. Day 3-4 - deck boards and railing. Day 5 - stairs and finishing. Larger decks (500+ sq ft) or complex multi-level designs take 1-2 weeks. DIY deck construction takes 3-5× longer: expect 10-15 full days (2-3 weekends) for 240 sq ft deck. First-timers should budget 15-20 days. Factors affecting timeline: concrete curing (24-48 hours before loading), weather delays (can't pour concrete in rain or freezing temps), permit inspections (may require multiple visits), and material delivery delays. Schedule decks for dry weather, allow buffer time for inspections and concrete curing.
4What is the best wood for decks?
Pressure-treated Southern Yellow Pine offers best value for most homeowners: costs $2-4 per linear foot, lasts 15-20 years with annual maintenance, and is widely available. PT lumber resists rot and insects due to chemical treatment and handles structural loads well. Downsides: requires annual cleaning and staining ($1-2 per sq ft), shows weathering/cracking if not maintained, and can warp. Cedar costs more ($5-8 per linear foot) but resists rot naturally without chemicals, looks beautiful, and doesn't require treatment (though recommended for longevity). Cedar works well for decking and railings but PT should be used for structural framing (stronger). Tropical hardwoods (IPE, Tigerwood) cost $8-15 per linear foot, last 30-50 years, and need no treatment but are expensive and very hard to work with (requires special saw blades, pre-drilling all fasteners).
5Do I need a permit to build a deck?
Permit requirements vary by jurisdiction. Many areas allow permit-free decks under these conditions: less than 200 sq ft, less than 30 inches above grade, not attached to house, and setback 5+ feet from property lines. Decks exceeding these limits typically require permits ($100-500), plans/drawings ($0-800 depending on complexity), and inspections (footing, framing, final). Some jurisdictions require permits for all decks regardless of size. Homeowners Association approval may be needed (separate from building permit). Building without required permits risks fines ($500-5,000), forced removal, inability to sell home (shows on title search), and insurance denial of claims for deck-related injuries. Always check with local building department before starting—call or visit their website for specific requirements.
6How much does composite decking cost vs wood?
Composite decking costs $4-10 per linear foot versus $2-4 for pressure-treated wood—about 2-3× more initially. For a 240 sq ft deck: PT lumber decking costs $700-1,000, composite costs $1,500-2,500. However, total cost of ownership over 20 years differs: PT requires annual cleaning ($100-200) and staining every 2-3 years ($300-500 per application) = $2,000-4,000 maintenance over 20 years. Composite requires occasional cleaning only ($100-200 total over 20 years). PT also needs replacement at 15-20 years; composite lasts 25-30 years. Twenty-year comparison: PT costs $3,000 initial + $3,000 maintenance + $3,000 replacement = $9,000 total. Composite costs $5,500 initial + $200 maintenance = $5,700 total. Composite saves money long-term despite higher up-front cost.
7Can I build a deck directly on the ground?
No, building a deck directly on ground causes rapid rot failure and violates building codes. All deck framing must be elevated above ground with airflow underneath to prevent moisture accumulation. Minimum clearances: 6-8 inches between deck joists and ground in well-drained areas, 12-18 inches in poor drainage areas. Decks require concrete footings below frost line supporting posts that elevate beams and joists. Ground-contact pressure-treated lumber (.40 PCF or higher retention) must be used for posts and any lumber within 6 inches of ground. Even PT lumber rots quickly in constant ground contact. For ultra-low decks, use deck blocks or poured footings with 6×6 posts cut short (12-18 inches tall) supporting beams directly, then joists on top. This creates minimal elevation while providing required airflow and code compliance.