Guides · 7 min read
What Does It Cost to Build a Deck in the Thousand Islands?
Straight numbers on what a new deck actually costs up here in 2026, what drives the price, and what waterfront wind, freeze-thaw and our short season do to a deck on the river.
The short answer
You came for numbers, so here they are. In the Thousand Islands and Jefferson County in 2026, a straightforward pressure-treated wood deck runs roughly $30 to $50 a square foot installed. A composite or PVC deck with quality railing lands around $55 to $90 a square foot. So a 300-square-foot deck might run $9,000 to $15,000 in treated lumber, or $16,000 to $27,000 in composite, give or take.
Those are real ranges for our area, and the spread is wide on purpose because decks vary so much. A simple platform off the back door is one thing. A multi-level deck stepping down a riverbank to a dock, with stairs, a wind-rated railing and a hot-tub-rated section, is another animal entirely. The footings, the elevation and the materials move the number more than the square footage alone.
What drives the price
A handful of things set almost every deck quote. Material is the first. Pressure-treated lumber is the budget choice and still the most common up here. Composite and PVC cost more upfront but skip the yearly staining and last longer, which matters a lot on a place you only visit in summer. The second driver is height and complexity. A ground-level deck is far cheaper than one elevated ten feet over a sloped riverbank with stairs down to the water.
Third is the footings, and up here that's a bigger deal than people expect. Our frost line is deep, so footings have to go down below it, often four feet or more, or the deck heaves and twists with every freeze-thaw cycle. On a rocky river lot or a steep bank, getting those footings in is real work. Fourth is railing, which is its own line item and ranges from basic to cable or glass. Fifth is the extras: built-in benches, lighting, a pergola, stairs and gates all add up.
Wood vs composite up here
This is the question we get most, and the honest answer depends on how you use the place. Pressure-treated wood costs less to build, but it needs cleaning and staining every year or two to hold up, and a deck on the river takes a beating from sun, damp and wind. If you're year-round and you don't mind the upkeep, treated wood is a fine, affordable choice.
Composite and PVC cost more at the start but they don't need staining, they don't splinter, and they shrug off the moisture and sun far better. For seasonal cottage owners, that low-maintenance part is a big deal, because nobody wants to spend their first weekend on the river sanding and sealing a deck. Composite has come a long way and the good brands look sharp and carry long warranties. We'll lay out the real cost difference both ways so you can decide based on your situation, not a sales pitch.
The waterfront factor
Building a deck on the St. Lawrence isn't the same as building one in a Watertown backyard, and the water changes a few things. Wind is the big one. Open water off the river and Lake Ontario means a waterfront deck and its railing take real wind load, so the framing, the connections and the railing all have to be built for it. A flimsy deck on an exposed point doesn't last.
Then there's the constant damp and the spray. A deck close to the water lives in a wetter, harder environment than one inland, which pushes a lot of river owners toward composite and stainless or coated hardware that won't rust out. And if your deck is near the shoreline, there can be permitting and setback rules tied to the waterfront. We handle that as part of the job, because building too close to the water without the right approvals is a headache you don't want.
Footings, frost and why they matter
We'll say more about footings because they're the part that decides whether a deck lasts or fails, and up here they're unforgiving. Our deep frost line means a footing that doesn't go below it will get pushed up by frozen ground every winter. Do that and within a few years your deck is racked, the boards have gaps and the stairs don't line up. We see it on cheap decks all the time.
Done right, the footings go down past the frost line and tie into proper posts and beams, so the deck stays put through every freeze-thaw cycle. On rocky river lots, that sometimes means more work to get a solid footing, and that shows up in the price. It's not a place to cut corners. A deck is only as good as what holds it up, and the part you can't see once it's built is the part that determines how long you get to enjoy it.
Where you can save and where you shouldn't
If the budget's tight, the smartest savings are in size and shape. A simpler rectangular deck costs far less per foot to build than a multi-level design with lots of angles and stairs. Keeping it close to ground level avoids expensive elevated framing and long stair runs. And treated lumber over composite is real money saved upfront if you're willing to do the maintenance.
The places not to cut are the footings, the framing, the connections and the hardware. Cheap footings heave. Undersized framing sags and bounces. The wrong fasteners on a treated deck corrode and stain. And skipping the permit to save time can bite you when you sell or if something fails. Whoever you hire should be fully insured and give you a written quote with a firm price and a real schedule. A lowball number on a deck usually means thin footings or a cut corner you'll find later.
Build it before the season slips away
Our deck season is short, and that's worth planning around. The window to build runs from spring once the ground thaws through fall before it freezes again, and the early summer rush books up fast. If you want a new deck ready for the heart of cottage season, the time to get on the schedule is well before you actually want to be sitting on it.
The only way to get a real number is to have someone look at your site, your slope, your access and how you want to use the deck. We come out, take measurements, talk through materials and figure out what the footings and elevation really involve. Then you get a written quote with a firm price and a schedule. Give us a call at (315) 350-3357 and we'll come take a look. The walkthrough is free.
Common questions
How much does it cost to build a deck in the Thousand Islands in 2026?
A pressure-treated wood deck runs roughly $30 to $50 a square foot installed, and a composite or PVC deck with quality railing runs about $55 to $90 a square foot. So a 300-square-foot deck might run $9,000 to $15,000 in treated lumber or $16,000 to $27,000 in composite. Height, footings, stairs and railing move the number more than square footage alone.
Is composite decking worth it on the river?
For a lot of seasonal owners, yes. Composite and PVC cost more upfront but they don't need yearly staining, they don't splinter, and they handle the damp, sun and wind off the river far better than wood. If you don't want to spend your first weekend on the river sanding and sealing, the low maintenance is usually worth the higher build cost.
Why do deck footings cost so much up here?
Our frost line is deep, so footings have to go down below it, often four feet or more, or the deck heaves and racks with every freeze-thaw cycle. On rocky or steep river lots, getting solid footings in is real work. It's the part you can't see once the deck is built, and it's the single biggest factor in whether the deck lasts or fails.
Do I need a permit to build a deck in Jefferson County?
Usually yes, and a waterfront deck may also have shoreline setback rules to deal with. We handle the permitting and any waterfront approvals as part of the project. Building a deck without the right permits, especially near the water, can cause real problems when you sell, so it's not a corner worth cutting to save time.
When should I schedule a deck build for cottage season?
Get on the schedule well before you want to use it. The build window runs from spring after the ground thaws through fall before it freezes, and the early summer rush fills up fast. If you want a deck ready for the heart of cottage season, booking in the off-season or early spring is the safest way to make sure it's done in time.
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