20×18 Deck Cost in Alaska
A 20×18 (360 sqft) deck in Alaska costs $23,040-$36,720 in mid-tier composite with the state's 1.28× labor multiplier (West). An 18×20 deck (360 sqft) is upper-mid — generous for entertaining without fully committing to wraparound complexity. Alaska's brutal frost depth (up to 60″) drives footing cost — sonotube + concrete can be 30-40% of total project cost. Labor 1.28× national.
5 finish tiers — 20×18 in Alaska
National $/sqft × Alaska's 1.28× labor multiplier × 360 sqft = total installed cost. Materials + labor + standard railing included.
Excludes permit ($218-$537 typical in Alaska), demolition (if replacing), and exceptional framing for 60″ frost depth. Anchorage requires 42″ frost depth on footings; Fairbanks 60″+. Permits $250-400.
20×18 framing notes for Alaska
Alaska considerations
Get a precise quote for your 20×18 deck in Alaska
Open the Deck Cost Calculator with AK pre-selected and dial in your exact size, framing, material, and railing choices.
FAQ — 20×18 deck in Alaska
How much does a 20×18 deck cost in Alaska?▾
In Alaska, a 20×18 (360 sqft) deck costs $11,520-$18,360 in pressure-treated, $23,040-$36,720 in mid-range composite (Trex Transcend / Fiberon Sanctuary), and $34,560-$50,760 in luxury composite/PVC (TimberTech AZEK / Trex Signature). Numbers reflect Alaska's 1.28× labor multiplier on 2026-Q1 retail.
What's the cheapest way to build a 20×18 deck in Alaska?▾
Cheapest = ground-level pressure-treated pine with no railings (where exempt under 30″ height) — ~$9,216-$13,824 in Alaska. Add stairs + railings + above-grade framing and the build goes to ~$12,902-$18,432. DIY saves 30-50% on labor but requires permit + inspection coordination yourself.
How long does it take to build a 20×18 deck in Alaska?▾
Permit timeline in Alaska: 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 Alaska?▾
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. Alaska's frost depth is 60″ — 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 Alaska?▾
Over 25 years in Alaska: PT pine = ~$13,824 install + ~$28,800 maintenance (stain every 2-3 yr) = $42,624 total. Mid composite = ~$26,726 install + $0 maintenance = $26,726 total. Composite wins by 59-81% over 25-yr lifecycle PLUS better resale value in Alaska's market.