Deck Building Cost in St. Louis, MO (2026)
Updated October 2026 · St. Louis, MO · index 1.12
How much does it cost to build a deck in St. Louis? For a 300 sq ft deck with pressure-treated wood, homeowners in St. Louis, MO pay about $12,600 on average, and most quotes land between $8,700 and $16,500 — $29 to $55 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 St. Louis runs 12% above the U.S. average: construction labor in the St. Louis area runs 21% above the national mean, materials 2% below. The same job averages $11,300 nationally and about $11,500 at the Missouri statewide index.
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Deck building price in St. Louis by decking material
What a 300 sq ft deck costs in St. Louis with each decking material, installed:
| Option | Average · range |
|---|---|
| Pressure-treated woodtreated pine or fir boards, stained and sealed$42 per sq ft | $12,600$8,700 – $16,500 |
| Capped compositehidden fasteners and a picture-frame border$50 per sq ft | $15,100$10,700 – $19,500 |
The least expensive option in St. Louis is pressure-treated wood, at about $12,600; capped composite averages $15,100, 1.2 times as much.
Cost to build a deck in St. Louis by size
With pressure-treated wood, priced for St. Louis, MO:
| Size | Average · range |
|---|---|
| A 200 sq ft deck$45 per sq ft | $9,050$6,200 – $11,900 |
| A 300 sq ft deck$42 per sq ft | $12,600$8,700 – $16,500 |
| A 400 sq ft deck$40 per sq ft | $16,100$11,200 – $21,000 |
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 St. Louis includes
Line by line, the $12,600 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 – $1,250 |
| Ground prep, fabric and gravel | $250 – $620 |
| Footings below the frost line | $460 – $930 |
| Flashed ledger on the house | $280 – $540 |
| 6x6 posts | $310 – $620 |
| Beams | $280 – $540 |
| Joist framing with hangers | $1,600 – $2,700 |
| Deck boards | $1,500 – $2,200 |
| One set of stairs (4 steps) | $580 – $1,150 |
| Railing | $2,100 – $3,650 |
| Fascia and skirting | $400 – $960 |
| Final inspection and cleanup | $160 – $410 |
| Stain and seal, two coats | $370 – $870 |
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 St. Louis's index of 1.12; permit fees are not scaled.
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What affects deck building prices in St. Louis
Labor and materials in St. Louis
Construction wages in the St. Louis metro run 13% above the U.S. mean (BLS, May 2025), and specialty-contractor pay in the city's county moves that up by 7%, to 21% above the national mean. Materials in the area's ZIP codes price 2% below the national average. Together they give St. Louis a construction cost index of 1.12.
Where St. Louis sits in Missouri
St. Louis is the most expensive of the 4 Missouri cities in our index, against a statewide index of 1.02. Springfield is the least expensive at 0.97.
Against the rest of the country
Of the 306 U.S. cities in JobFlex's index, St. Louis ranks 70th from the most expensive. The job that averages $12,600 here averages $11,300 at the national rate.
Frost depth in Missouri
Deck footings go below the frost line, or they heave by the second spring. The typical code frost depth in Missouri is about 24 in.. Your building department sets the exact figure.
The deck code in Missouri
There is no statewide code; decks follow the International Residential Code as the cities and counties of Missouri adopt it (St. Louis County: 2015 IRC with county amendments; Independence: 2024 IRC; St. Charles County: 2021 IRC). 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.
What decks are built of in Missouri
Most used on decks in the Plains states: treated pine, then capped composite, then cedar.
Sales tax in Missouri
Missouri's base state sales tax is 4.225%, and cities and counties can add their own. How it applies to a home-improvement contract varies, so ask whether a quote includes it. Prices on this page are before tax.
What a St. Louis contractor will ask before quoting
- Reuse the frame or rebuild?
- Height, railing style and stairs
- Board brand and color
Deck building cost in other Missouri cities
A 300 sq ft deck with pressure-treated wood averages $12,600 in St. Louis; $11,800 in Kansas City, $10,900 in Springfield, $11,400 in Jefferson City.
| City | Average · range |
|---|---|
| Kansas City, MO6% less | $11,800$8,150 – $15,500 |
| Springfield, MO13% less | $10,900$7,550 – $14,300 |
| Jefferson City, MO10% less | $11,400$7,850 – $14,900 |
deck building price in St. Louis: questions
How much does it cost to build a deck in St. Louis, MO?
About $12,600 for a 300 sq ft deck with pressure-treated wood, and most St. Louis quotes fall between $8,700 and $16,500. That is 12% above the U.S. average, where the same job averages $11,300.
What is the deck price per square foot in St. Louis?
$29 to $55 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 St. Louis?
$11,200 to $21,000, about $16,100 on average, with pressure-treated wood — $40 per sq ft.
Do you need a permit for deck building in St. Louis?
Yes — a new deck needs a permit nearly everywhere, St. Louis included. In Missouri, decks follow the International Residential Code as the cities and counties of Missouri adopt it (St. Louis County: 2015 IRC with county amendments; Independence: 2024 IRC; St. Charles County: 2021 IRC). The prices on this page carry $410–$1,250 for plans, permit and layout.
Does the price include sales tax in Missouri?
No. The prices here are before tax; Missouri's base state rate is 4.225%, plus any local rate.
What decking do people choose in Missouri?
Most used on decks in the Plains states: treated pine, then capped composite, then cedar.
Other home projects in St. Louis
Deck building cost in Missouri
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 St. Louis's construction cost index of 1.12.
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 St. Louis, each on its own base: Craftsman 1.08. Treat any city figure as about ±5%; a contractor's quote for your house is the number to plan with.
Contractors in St. Louis 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