How to use this calculator
Enter your deck's length, width, and height off the ground. The height affects post length and the number of footings needed. Higher decks require longer posts and more structural support.
Choose your decking material to see how it affects both material cost and estimated labor rates. Toggle railing and stairs on or off based on your plans. The calculator updates in real time with a full materials breakdown, DIY cost, and contractor estimate.
Decking materials comparison
| Material | Cost/sq ft | Lifespan | Maintenance |
|---|---|---|---|
| Pressure Treated | $2 to $3 | 15 to 20 years | Annual stain & seal |
| Cedar | $4 to $5 | 20 to 25 years | Stain every 2 to 3 years |
| Composite | $5 to $7 | 25 to 30 years | Occasional cleaning |
| Trex / Premium | $7 to $10 | 25 to 50 years | Minimal cleaning |
Permits and building codes
Most municipalities require a building permit for any deck that is attached to the house, elevated more than 30 inches, or exceeds 200 square feet. Permit fees typically range from $100 to $500 depending on your location and deck size.
Building codes specify requirements for post spacing, joist size, railing height (typically 36 inches for residential, 42 inches for commercial), baluster spacing (no more than 4 inches apart), and ledger board attachment. Your local inspector will check these during the required inspections.
Does a deck add value to your home?
A well-built deck typically recoups 65 to 75% of its cost at resale. Wood decks tend to return slightly more than composite in most markets, but composite's low maintenance and longer lifespan make it increasingly popular with buyers. A basic 300 sq ft pressure-treated deck can add $6,000 to $10,000 to your home's value.
The best ROI comes from decks that are well-proportioned to the house, properly maintained, and include functional features like built-in seating or lighting. Oversized or overly elaborate decks rarely recover their full investment.
Frequently asked questions
How much does it cost to build a 12x20 deck?
A 12x20 (240 sq ft) deck costs roughly $1,200 to $2,500 for materials only with pressure-treated wood, or $3,500 to $6,000 with composite decking. Hiring a contractor adds $15 to $35 per square foot for labor, bringing the total to $4,800 to $14,400 depending on material and complexity.
Is it cheaper to build a deck yourself?
Building a deck yourself typically saves 40 to 60% compared to hiring a contractor. A DIY pressure-treated deck costs about $8 to $15 per square foot in materials, while a contractor charges $25 to $40 per square foot total. However, DIY requires tools, skills, and significant time.
How long does a pressure-treated deck last vs composite?
Pressure-treated wood decks last 15 to 20 years with proper annual maintenance. Composite decking lasts 25 to 30+ years with virtually no maintenance beyond occasional cleaning. While composite costs more upfront, the lifetime cost is often comparable when you factor in annual staining and sealing.
Do I need a permit to build a deck?
Most jurisdictions require a building permit for decks attached to the house, more than 30 inches off the ground, or over 200 square feet. Permit costs typically range from $100 to $500. Building without a required permit can result in fines or complications when selling your home.