20×18 Deck Cost in New Hampshire
A 20×18 (360 sqft) deck in New Hampshire costs $21,960-$35,280 in mid-tier composite with the state's 1.22× labor multiplier (Northeast). An 18×20 deck (360 sqft) is upper-mid — generous for entertaining without fully committing to wraparound complexity. New Hampshire labor 1.22× national. Frost depth 48″.
5 finish tiers — 20×18 in New Hampshire
National $/sqft × New Hampshire's 1.22× labor multiplier × 360 sqft = total installed cost. Materials + labor + standard railing included.
Excludes permit ($240-$592 typical in New Hampshire), demolition (if replacing), and exceptional framing for 48″ frost depth. NH permits $200-340.
20×18 framing notes for New Hampshire
New Hampshire considerations
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FAQ — 20×18 deck in New Hampshire
How much does a 20×18 deck cost in New Hampshire?▾
In New Hampshire, a 20×18 (360 sqft) deck costs $11,160-$17,640 in pressure-treated, $21,960-$35,280 in mid-range composite (Trex Transcend / Fiberon Sanctuary), and $33,120-$48,240 in luxury composite/PVC (TimberTech AZEK / Trex Signature). Numbers reflect New Hampshire's 1.22× labor multiplier on 2026-Q1 retail.
What's the cheapest way to build a 20×18 deck in New Hampshire?▾
Cheapest = ground-level pressure-treated pine with no railings (where exempt under 30″ height) — ~$8,784-$13,176 in New Hampshire. Add stairs + railings + above-grade framing and the build goes to ~$12,298-$17,568. DIY saves 30-50% on labor but requires permit + inspection coordination yourself.
How long does it take to build a 20×18 deck in New Hampshire?▾
Permit timeline in New Hampshire: 2-6 weeks depending on jurisdiction. Construction time for a 20×18: pro crew = 5-8 days for framing + boards + railings + stairs. DIY = 3-5 weekends for experienced DIYer. Allow extra time for permit approval + inspections.
What framing do I need for a 20×18 deck in New Hampshire?▾
IRC R507-compliant framing for a 20×18 deck typically uses 2×8 joists at 16″ OC for spans up to 12 ft, 2×10 joists for spans 12-16 ft. New Hampshire's frost depth is 48″ — footings must extend below that per IRC R403.1.4. Deep frost requires more concrete per footing — budget extra for sonotubes + concrete. Verify with your local building department.
Is composite worth it for a 20×18 deck in New Hampshire?▾
Over 25 years in New Hampshire: PT pine = ~$13,176 install + ~$27,450 maintenance (stain every 2-3 yr) = $40,626 total. Mid composite = ~$25,474 install + $0 maintenance = $25,474 total. Composite wins by 59-81% over 25-yr lifecycle PLUS better resale value in New Hampshire's market.