A 20×20 composite deck costs $16,000 to $34,000 installed in 2026, with most projects landing near $25,000. That works out to $40.00 – $85.00 per sq ft. Your state changes the number — use the calculator below.
20×20 Composite Deck cost calculator
Planning estimate only. State pricing applies a construction wage index to the labor share; materials are held at national prices. Get three written quotes before committing.
20×20 Composite Deck cost by state
Labor is about 42% of the bill, so the same 20×20 project swings widely between states:
| Cheapest states | Cost | Priciest states | Cost |
|---|---|---|---|
| Mississippi | $23,110 | Hawaii | $27,940 |
| Arkansas | $23,215 | California | $27,310 |
| Alabama | $23,320 | New York | $27,100 |
| South Dakota | $23,425 | Massachusetts | $26,890 |
| West Virginia | $23,530 | Washington | $26,680 |
What fits on a 20×20 composite deck?
A 20×20 deck supports separate dining and lounging zones, or a hot tub plus seating. At this size, framing span, footing count, and railing length all climb noticeably.
Cost by grade and finish
Specification moves the price as much as size does. For a 20×20 project:
| Option | Typical cost | vs standard |
|---|---|---|
| Pressure-treated pine | $25,000 | baseline |
| Cedar | $31,250 | +25% |
| Composite (entry) | $38,750 | +55% |
| Composite (premium) | $48,750 | +95% |
How 20×20 compares with nearby sizes
| Size | Installed cost | vs 20×20 |
|---|---|---|
| 8×10 | $5,000 | -80% |
| 10×10 | $6,250 | -75% |
| 10×12 | $7,500 | -70% |
| 12×12 | $9,000 | -64% |
| 12×16 | $12,000 | -52% |
| 12×20 | $15,000 | -40% |
What the price includes
The range above covers materials, labor, standard site preparation, and cleanup for a 20×20 project with normal access. It excludes permits, demolition or removal of existing work, drainage corrections, and upgrades beyond a standard specification.
Materials alone run roughly $14,500 for this size, which is the figure to start from if you are weighing doing it yourself.
What changes the price of a 20×20 composite deck
Height above grade
A ground-level deck needs fewer footings and no stairs or guardrail. Raising it changes framing, footing depth, and code requirements together.
Decking material
Pressure-treated pine is the baseline. Cedar, entry composite, and premium composite each step the material cost up substantially.
Railing
Railing is priced per linear foot and is one of the largest single line items. Cable and glass infill cost far more than standard balusters.
Footings and frost depth
In cold states, footings must reach below the frost line, which multiplies excavation and concrete on the same footprint.
Stairs
Every step adds framing, treads, and often a second handrail. Multi-level decks climb quickly for this reason.
How long does a 20×20 composite deck take?
A 20×20 deck usually runs one to two weeks of build time, longer if it is elevated or multi-level. Permit approval before that can add several weeks depending on your jurisdiction.
Frequently asked questions
How much does a 20×20 composite deck cost?
A 20×20 composite deck costs $16,000 to $34,000 installed in 2026, averaging about $25,000. State labor rates move that figure by 20% or more in either direction.
How much is that per sq ft?
It works out to $40.00 to $85.00 per sq ft. Larger projects usually land slightly lower per sq ft because setup and mobilisation costs spread across more area.
What would it cost to do it myself?
Materials for a 20×20 project run roughly $14,500. The rest is labor, equipment, and disposal. Factor in tool rental and the cost of correcting mistakes before deciding.
Which states are cheapest for this project?
Mississippi and Arkansas are among the lowest at around $23,110, while Hawaii runs closer to $27,940 for the same specification.
How long does a 20×20 composite deck take to complete?
A 20×20 deck usually runs one to two weeks of build time, longer if it is elevated or multi-level. Permit approval before that can add several weeks depending on your jurisdiction.
What most often pushes a 20×20 project over budget?
Height above grade and decking material are the two most common. A ground-level deck needs fewer footings and no stairs or guardrail. Raising it changes framing, footing depth, and code requirements together.
Do I need a permit for a 20×20 composite deck?
Most jurisdictions require a permit for work of this type and value, and the fee commonly scales with declared project value. Budget a few hundred dollars and confirm with your local building department before work starts, since unpermitted work can surface during a sale or an insurance claim.
Other composite deck sizes
Open the full composite deck calculator →