Deck Building Cost in Portsmouth, NH (2026)
Updated October 2026 · Portsmouth, NH · index 1.11
How much does it cost to build a deck in Portsmouth? For a 300 sq ft deck with pressure-treated wood, homeowners in Portsmouth, NH pay about $12,500 on average, and most quotes land between $8,650 and $16,300 — $29 to $54 per sq ft. The price covers plans and the permit, footings, a framed and flashed structure, the deck boards, railing, one set of stairs, fascia and cleanup.
The deck building price in Portsmouth runs 11% above the U.S. average: construction labor in the Portsmouth area runs 18% above the national mean, materials 1% above. The same job averages $11,300 nationally and about $11,100 at the New Hampshire statewide index.
Deck Building cost calculator for Portsmouth
100 to 800 sq ft
Are you a deck builder? Price jobs like this in 60 seconds
Deck building price in Portsmouth by decking material
What a 300 sq ft deck costs in Portsmouth with each decking material, installed:
| Option | Average · range |
|---|---|
| Pressure-treated woodtreated pine or fir boards, stained and sealed$42 per sq ft | $12,500$8,650 – $16,300 |
| Capped compositehidden fasteners and a picture-frame border$50 per sq ft | $15,000$10,600 – $19,300 |
The least expensive option in Portsmouth is pressure-treated wood, at about $12,500; capped composite averages $15,000, 1.2 times as much.
Cost to build a deck in Portsmouth by size
With pressure-treated wood, priced for Portsmouth, NH:
| Size | Average · range |
|---|---|
| A 200 sq ft deck$45 per sq ft | $9,000$6,150 – $11,800 |
| A 300 sq ft deck$42 per sq ft | $12,500$8,650 – $16,300 |
| A 400 sq ft deck$40 per sq ft | $16,000$11,100 – $20,900 |
Some costs stay the same whatever the size — plans, permit and layout, one set of stairs (4 steps), final inspection and cleanup — so a bigger job costs less per unit: $40 per sq ft for a 400 sq ft deck against $45 for a 200 sq ft deck.
What a deck building in Portsmouth includes
Line by line, the $12,500 average for a 300 sq ft deck breaks down like this: 47% labor, 53% materials and equipment.
| Line | Low – high |
|---|---|
| Plans, permit and layout | $410 – $1,200 |
| Ground prep, fabric and gravel | $240 – $610 |
| Footings below the frost line | $460 – $920 |
| Flashed ledger on the house | $280 – $540 |
| 6x6 posts | $310 – $610 |
| Beams | $280 – $540 |
| Joist framing with hangers | $1,600 – $2,700 |
| Deck boards | $1,450 – $2,200 |
| One set of stairs (4 steps) | $570 – $1,150 |
| Railing | $2,100 – $3,650 |
| Fascia and skirting | $400 – $960 |
| Final inspection and cleanup | $160 – $410 |
| Stain and seal, two coats | $370 – $860 |
Each line is the price book's U.S. rate for that step, scaled by 0.74 to the installed price published sources give for the whole job (see how these prices are built), times Portsmouth's index of 1.11; permit fees are not scaled.
Get free quotes from Portsmouth contractors
Describe your project once and JobFlex sends it to a local deck builder who prices it for your home — free, no account needed.
What affects deck building prices in Portsmouth
Labor and materials in Portsmouth
Construction wages in the Portsmouth metro run 27% above the U.S. mean (BLS, May 2025), and specialty-contractor pay in the city's county moves that down by 7%, to 18% above the national mean. Materials in the area's ZIP codes price 1% above the national average. Together they give Portsmouth a construction cost index of 1.11.
Where Portsmouth sits in New Hampshire
Portsmouth is the most expensive of the 4 New Hampshire cities in our index, against a statewide index of 0.99. Concord is the least expensive at 0.98.
Against the rest of the country
Of the 306 U.S. cities in JobFlex's index, Portsmouth ranks 75th from the most expensive. The job that averages $12,500 here averages $11,300 at the national rate.
Frost depth in New Hampshire
Deck footings go below the frost line, or they heave by the second spring. The typical code frost depth in New Hampshire is about 48 in. — deep holes, more concrete and more digging time than in the South. Your building department sets the exact figure.
The deck code in New Hampshire
Decks here are built to the New Hampshire State Building Code (2024 IRC with New Hampshire amendments). Guards are required at 36 in. where the deck is more than 30 in. up, and stair risers can be up to 7.75 in. Through December 31, 2026 an applicant may still build to the 2021 IRC edition (RSA 155-A:2).
What decks are built of in New Hampshire
Most used on decks in New England: treated pine, then capped composite, then PVC.
Sales tax in New Hampshire
New Hampshire has no state sales tax. Prices on this page are before any tax.
What a Portsmouth contractor will ask before quoting
- Reuse the frame or rebuild?
- Height, railing style and stairs
- Board brand and color
Deck building cost in other New Hampshire cities
A 300 sq ft deck with pressure-treated wood averages $12,500 in Portsmouth; $11,000 in Concord, $11,100 in Nashua, $11,100 in Manchester.
| City | Average · range |
|---|---|
| Concord, NH12% less | $11,000$7,650 – $14,400 |
| Nashua, NH11% less | $11,100$7,700 – $14,600 |
| Manchester, NH11% less | $11,100$7,700 – $14,600 |
deck building price in Portsmouth: questions
How much does it cost to build a deck in Portsmouth, NH?
About $12,500 for a 300 sq ft deck with pressure-treated wood, and most Portsmouth quotes fall between $8,650 and $16,300. That is 11% above the U.S. average, where the same job averages $11,300.
What is the deck price per square foot in Portsmouth?
$29 to $54 per sq ft, about $42 on average with pressure-treated wood. Smaller jobs cost more per unit, because the fixed costs are spread over less.
How much is a 400 sq ft deck in Portsmouth?
$11,100 to $20,900, about $16,000 on average, with pressure-treated wood — $40 per sq ft.
Do you need a permit for deck building in Portsmouth?
Yes — a new deck needs a permit nearly everywhere, Portsmouth included. In New Hampshire, decks follow the New Hampshire State Building Code (2024 IRC with New Hampshire amendments). The prices on this page carry $410–$1,200 for plans, permit and layout.
Does the price include sales tax in New Hampshire?
No tax is included, and New Hampshire has no state sales tax.
What decking do people choose in New Hampshire?
Most used on decks in New England: treated pine, then capped composite, then PVC.
Other home projects in Portsmouth
Deck building cost in New Hampshire
How these prices are built
Every price on this page comes from JobFlex's contractor price book: what a homeowner pays a licensed contractor for each step of the job, as a U.S. national average per unit, with the contractor's overhead and profit included and sales tax left out. The deck building is priced step by step, then multiplied by Portsmouth's construction cost index of 1.11.
Where the price book's steps for an option add up to more than 20% over the installed price a published source gives for the whole job, every step but a permit fee is scaled down to the middle of that range: pressure-treated wood × 0.74 (HomeGuide 2026: $25–$50 per sq ft); capped composite × 0.80 (Ergeon 2026: $30–$60 per sq ft).
The index weighs local construction wages (BLS Occupational Employment and Wage Statistics, May 2025) at 60% and the area's material prices (Craftsman ZIP-area factors) at 40%. Published indices for Portsmouth, each on its own base: RSMeans residential 0.95, HUD 1.02, Craftsman 1.06. Treat any city figure as about ±5%; a contractor's quote for your house is the number to plan with.
Contractors in Portsmouth build quotes like these with JobFlex's Deck Studio.
- HomeGuide 2026: pressure-treated deck $25-$50/sqft installed, labor $15-$30/sqft
- Ergeon 2026: composite deck $30-$60/sqft installed
- HomeGuide 2026: composite railing $25-$60/lf, aluminum $50-$200/lf installed