240 sqft · 12×20 ft

12×20 Deck Cost

A 12×20 deck (240 sqft) is a long, narrow deck — common for ranch-style homes with a long back wall. The calculator below is pre-loaded with these dimensions — change the state, finish tier, or scope to recalculate live.

Get 2–3 free quotes

240 sqft64 ft perimeter5 finish tiersAll 50 states2026-Q1 pricing

12×20·Footprint

240·Sq ft

64·Perimeter ft

<2s·Live calc

How much a 12×20 deck costs by material

Material$/sqft installed12×20 total (240 sqft)

Pressure-treated wood

Cheapest to build; re-stain every ~2 years.

$25–$40$6,000–$9,600

Cedar / premium PT

Warmer look than PT; ages to silver, re-stain every ~3 years.

$35–$55$8,400–$13,200

Composite — mid-range

Trex Enhance, Fiberon Good Life. Wash-only; best 25-year value for most.

$50–$80$12,000–$19,200

Composite / PVC — premium

Trex Transcend, TimberTech AZEK. Longest warranty, coolest underfoot.

$75–$110$18,000–$26,400

Tropical hardwood (Ipe)

Ipe, Cumaru. Stunning and dense; pre-drill every fastener.

$90–$140$21,600–$33,600

A 12×20 deck is 240 sq ft. In pressure-treated wood that runs about $6,000–$9,600 installed — the cheapest way to get a deck this size, though you'll re-stain it every couple of years. Step up to mid-range composite (Trex Enhance, Fiberon Good Life) and the same 240 sq ft is $12,000–$19,200: roughly double the upfront, near-zero maintenance, and usually the lower 25-year cost.

Premium composite or PVC (Trex Transcend, TimberTech AZEK) lands around $18,000–$26,400, and tropical hardwood like Ipe tops out near $21,600–$33,600. These are installed (material + labor) for a simple rectangle — an L-shape adds ~10%, a wraparound ~22%, and a tall or hard-to-access deck up to 40%. Regionally, the South runs about 8% under these national figures and the West Coast about 28% over.

The calculator below itemizes a complete project — framing, footings, railing, stairs, permit, and contingency — so its total runs higher than the surface-and-labor bands above for the same size.

Inputs

Dimensions

Plan-view length × width.

Lengthft

Widthft

Area · 240 sq ft·Perimeter · 64 ft

Material tierinstalled $/sqft band

State2-letter · labor multiplier

Footprint shape1.00× complexity

AttachmentShares house structure

Deck heightinches

IRC R312 requires a 36″ guardrail above 30″.

Stairssteps

Site accessDriveway / wide-open backyard

Scope toggles

Project budget · Northeast

$19,709 – $34,581

$82–$144/ sq ft

240 sq ft · Mid composite · 1.22× labor · 1.10× complexity

Materials

Low $5,940

Labor

Low $8,857

Add-ons

Low $4,592

Soft costs

Permit · demo · design

Project advisories · IRC 2021

Guardrail included (deck 36″ off grade)

IRC R312

IRC R312 mandates a 36″ guardrail on open edges when deck height exceeds 30″. 44 lf priced at Mid composite tier.

Building permit included in budget

IRC R105

Northeast typical permit fee is in the budget. Most jurisdictions require a permit for decks > 200 sqft, > 30″ above grade, or attached to the house.

Hidden-fastener install premium baked in

Manufacturer specs

Mid composite uses hidden-fastener clip systems (Cortex / CamoClip / Trex Universal) — labor takes 25–30% longer than face-screwing PT. Already inside the tier's installed $/sqft band.

Cost breakdown

Materials27%$9,504
Labor41%$14,172
Add-ons22%$7,442
Soft costs1%$320
Contingency9%$3,144
Share of the high estimate. Switch tiers below to repaint the split.

Item

Qty

Total

Labor (Northeast, 1.22× national)

$8,857 – $14,172 (low – high estimate)

1.0 scope

$14,172

Labor (Northeast, 1.22× national)

$8,857 – $14,172 (low – high estimate)

1.0 scope

—

$14,172

Materials (decking + framing + hardware)

$5,940 – $9,504 (low – high estimate)

Home Depot Lowe’s

1.0 scope

$9,504

Materials (decking + framing + hardware)

$5,940 – $9,504 (low – high estimate)

Home Depot Lowe’s

1.0 scope

—

$9,504

Railing (44 lf, ledger 3-side)

$2,952 – $5,100 (low – high estimate)

1.0 scope

$5,100

Railing (44 lf, ledger 3-side)

$2,952 – $5,100 (low – high estimate)

1.0 scope

—

$5,100

Contingency (10% reserve)

up to $3,144

1.0 scope

$3,144

Contingency (10% reserve)

up to $3,144

1.0 scope

—

$3,144

Stairs (4 steps @ 9.0″ rise)

$1,640 – $2,342 (low – high estimate)

1.0 scope

$2,342

Stairs (4 steps @ 9.0″ rise)

$1,640 – $2,342 (low – high estimate)

1.0 scope

—

$2,342

Building permit (Northeast)

$320 flat

1.0 scope

$320

Building permit (Northeast)

$320 flat

1.0 scope

—

$320

Materials subtotal

$34,582

National-median pricing (2026-Q1). Local prices vary ±15%. Materials line uses Mid composite tier; switch tiers to repaint the budget. Includes 10% contingency reserve on the high estimate.

Live preview

Visualize your deck

Photoreal 3D · plan view · framing breakdown. Color matches your tier selection.

PBR materialsHDR lightingMid composite

Loading 3D scene…

DeckMath·20′ × 12′·240 sq ft

Trex Enhance·composite

Drag · pinch / scroll

Joists

16 × 12′

Beams

1 × 2-ply 2×10

Posts

4 × 6×6

Boards

27 rows

Project all-in

Materials (low – high)

Mid composite tier · Trex Enhance · Fiberon Good Life · TimberTech Prime+. ~$0.05/sqft/yr.

$5,940 – $9,504

Labor (installed)

Northeast · 1.22× national index

$8,857 – $14,172

Add-ons

Railing · stairs · lighting (only included items)

$4,592 – $7,442

Soft costs

Permit · demo · design (only included items)

$320 – $320

Contingency reserve (10%)

Industry-standard cushion for unforeseen scope

$3,144

Project total (low – high)

Plan around the high. Get 3 contractor bids — DeckMath should land within ±15%.

$19,709 – $34,581

Same dimensions, different tier

tap to switch

DIY savings

$16,971

vs mid-range contractor

Materials only: $9,504
Estimated hours: 360 hr
Skill required: advanced

Finance estimate

$701/month

60-month personal loan @ 7.99% APR

Principal: $34,581
Total interest: $7,480
Estimate only — shop 3+ lenders.

Composite/PVC installs use hidden-fastener clip systems — labor is 25–30% slower than face-screwing pressure-treated wood. That premium is already baked into the tier's installed $/sqft band.

Need exact board counts?

The Deck Material Calculator gives you a permit-ready bill of materials — every joist, hanger, fastener, and footing — validated against IRC 2021 span tables.

Open

Estimates use 2026-Q1 national-median pricing (Home Advisor, Angi, RSMeans). Expect ±15% variance vs your local market. Always get 3 contractor bids before signing. This calculator is not a substitute for a licensed inspector or structural engineer.

Estimated material takeoff — 12×20

The framing and decking a 12×20 (240 sqft) deck needs — board, joist, beam, post, footing, and railing quantities computed from the dimensions at 16″ joist spacing with a 10% waste factor.

Component

Quantity

How it's estimated

Decking boards (16′ × 5/4×6)

36 boards · 576 lf

240 sqft ÷ 5.5″ face × 10% waste

Joists (2×8 @ 16″ o.c.)

16 joists · 192 lf

⌈20′ × 12 ÷ 16″⌉ + 1, each 12′ long

Beam lumber (1× 2-ply built-up)

40 lf

1 beam line × 20′ × 2 plies

Posts (6×6 PT) + footings

4 posts · 4 footings

1 line × (⌈20′ ÷ 8⌉ + 1) posts at ≤8′ o.c.

Footing concrete (60-lb bags)

21 bags · 9.4 cu ft

4 piers @ 12″⌀ × 36″ deep — adjust depth to local frost line

Joist hangers (Simpson LUS)

16 hangers

one per joist at the ledger / beam connection

Railing run

44 lf

64 lf perimeter − 20′ ledger side

Decking face screws

≈ 1,152 screws

≈2 screws per board at each joist crossing

Decking

36 boards

576 lf incl. waste

Joists

16″ o.c. · 192 lf

Posts / footings

21 × 60-lb concrete

Railing

44 lf

64 lf perimeter

Estimated quantities for planning and budgeting — round up when ordering. Beam sizing, post spacing, and footing depth must follow your local code and a stamped plan (frost line, soil, and snow load vary by region per IRC 2021 / AWC DCA-6).

FAQ — 12×20 deck

How much does a 12×20 deck cost?

A 12×20 deck (240 sqft) costs $6,000-$9,600 for budget pressure-treated construction, $12,000-$19,200 for mid-range composite, and $21,600-$33,600 for premium composite or tropical hardwood. National-average pricing — multiply by 0.92× for the South or 1.28× for West Coast labor.

How many boards do I need for a 12×20 deck?

Running 5/4×6 or 1×6 deck boards (5.5″ face, 1/8″ install gap) parallel to the long dimension: rows = ceil(12 × 12 ÷ 5.625) = 26 rows. Total LF = 26 × 20 × 1.07 (7% waste, parallel pattern) ≈ 557 LF. Round up to 20-ft stock for typical 28 boards.

How long does it take to build a 12×20 deck?

For a contractor crew (2-3 people), a 12×20 deck takes 3-4 days depending on complexity, including framing + decking + railing + inspection wait. DIY single-person build: 36-45 weekend days for composite, less for pressure-treated.

Do I need a permit for a 12×20 deck?

In most US jurisdictions, yes. IRC 2021 R105 requires a permit for any deck above 30″ off grade, attached to the house, or larger than 200 sqft. A 12×20 deck (240 sqft) exceeds the 200-sqft threshold and definitely requires a permit.