Deck cost calculator for New Hampshire

How much does a deck cost in New Hampshire?

A 16 × 12 foot composite deck, 192 square feet with railing and a short flight of stairs, costs $6,900 to $9,340 installed in New Hampshire, or about $42.29 per square foot. The same deck in pressure-treated pine runs $5,420 to $7,330, in cedar $6,060 to $8,200, and in PVC $7,270 to $9,830.

New Hampshire labor runs about 5% above the national average, which shifts that composite deck up by roughly $123 against a national-average build. Labor is 40-50% of an installed deck, and it climbs further on elevated or complex-shaped decks where framing takes longer.

Building it yourself removes the labor line: the same composite deck comes to roughly $6,202 in materials, hardware, permit and tool rental. Decks are more forgiving DIY projects than fences in one respect and less in another. The framing is straightforward, but the ledger connection to the house is the single most safety-critical detail in residential construction, and it is the most common inspection failure.

What common deck sizes cost in New Hampshire

Most people arrive at this deck calculator with a size already in mind, so here are the four that get searched most, priced for New Hampshire. A 12 × 12 deck (144 sq ft) costs about $6,546 in composite. A 14 × 20 (280 sq ft) costs about $10,936, a 16 × 20 (320 sq ft) about $12,178, and a 20 × 20 (400 sq ft) about $14,662.

In pressure-treated pine those same footprints come down sharply, the 16 × 20 to $9,271 and the 20 × 20 to $11,028. That is the single largest saving available on any deck in New Hampshire.

Notice how little the per-square-foot figure moves between sizes: $39.06 on the 14 × 20 against $36.66 on the 20 × 20. The permit, the ledger and the stairs cost the same whatever the area, so they spread thinner as the deck grows. If you are undecided between two sizes, the larger one is almost always the better value per square foot.

Building a deck in New Hampshire

New Hampshire has an extreme 48-inch frost depth, among the deepest in the country, and the dominant cost factor on any post-set project. Deck footings have to reach below that line, and on a 16 × 12 deck that is six to nine footings, so frost depth drives the substructure budget more than any decking choice does.

The climate here is cold with heavy snow and a long freeze season, and ground conditions are rocky glacial till with frequent ledge. In practical terms: Snow load governs the framing spec, and the 48-inch footing depth dominates substructure cost.

Deep frost, rocky excavation and a short season all push concrete cost above the national average. That matters for a deck because every footing is a small concrete pour, and the same constraints that govern a slab govern the piers under your deck.

Composite and Trex decking in New Hampshire

Composite is the most common upgrade from pressure-treated pine here, and the reason is maintenance rather than price: it never needs sealing, which matters in a climate that is cold with heavy snow and a long freeze season. The composite deck calculator setting above prices boards at $9 per square foot, framing at $5 and installed labor at $10 before the New Hampshire multiplier of 1.05× is applied.

Trex is the brand most people mean when they say composite, and it is sold in tiers rather than at one price: Enhance Basics runs around $5 per square foot for boards alone, Select around $9, and the premium Transcend line around $12. TimberTech, Fiberon and Deckorators compete at each of those tiers. Whichever brand goes down, the framing, railing and labor underneath are identical, which is why installed totals differ far less than board prices suggest.

Snow load governs the framing spec, and the 48-inch footing depth dominates substructure cost. Weigh that against how long you plan to stay: over 25-30 years of service the composite deck above works out to $295 per year in New Hampshire against $510 for pressure-treated pine.

Deck permits and inspections in New Hampshire

Manchester and most New Hampshire towns require permits for fences over 6 feet and for decks over 30 inches; shoreland protection adds review near water.

Deck permits cost more than fence permits almost everywhere because structural review is involved. Our estimate carries $368 as a permit and inspection allowance for New Hampshire. Expect at least two inspections: one on the footings before concrete is placed, and one on the framing before decking goes down.

Do not skip the permit on a deck. An unpermitted deck surfaces during resale, and lenders and insurers both take an interest. Rebuilding a deck to code after the fact costs far more than permitting it correctly the first time.

How we calculated these estimates

Every figure on this page comes from the same open formula the calculator above uses. We start from a 2026 national baseline for materials and installed labor, apply the state labor multiplier published by the Bureau of Labor Statistics for construction trades, then add the line items your inputs call for: gates, corners, removal, permits and a waste allowance. Nothing is hidden behind a lead form, and no contractor pays us to appear here. The result is a planning range, not a quote. The low figure assumes straightforward access and an efficient crew, and the high figure assumes obstacles, difficult access, or premium material grades.