Deck quotes are confusing because two builders can price the “same” deck very differently — the number depends on material, height, stairs, railing, and your lot. Below we give you a calculator, real prices by size, and answer the eight cost questions homeowners ask most, so you know what to build a deck in Ontario should actually cost. This page is part of our complete guide to building a deck in Ontario.

How much does it cost to build a deck in Ontario?

Estimate your installed cost, then read the real prices by size below.

How much does a deck cost per square foot, and by size?

In 2026, budget about $45–$95 per square foot installed — so a 12 x 16 ft deck (192 sq ft) runs roughly $8,600–$18,000. Pressure-treated sits at the low end, composite at the high end, before extras like stairs, premium railing, or a raised height.

All figures CAD, installed, with standard railing and footings. Cedar generally lands between PT and composite.

How much more is composite vs pressure-treated?

Composite typically adds 40–60% over pressure-treated for a complete deck. PT lands around $45–$65/sq ft installed; composite around $65–$95. You pay more upfront but skip the staining for decades — see the full trade-off in our composite vs wood decking guide.

Why quotes vary, and what’s included

Why do contractor quotes vary so wildly?

Mostly scope, not price-gouging. One quote may include footings to frost depth, a railing upgrade, and stairs while another assumes the bare minimum. Access, soil, height, and finish choices all swing the labour. Compare what’s actually included before you compare the bottom-line numbers.

What’s actually included in a quote?

A complete quote spells out: footings and their depth, framing sizes, the decking, railing (and what grade), stairs, fasteners and flashing, the permit, and cleanup. Vague “allowances” are where surprises hide. Ask each builder to list exclusions and how change orders are priced before you sign.

Hidden costs people forget?

The costs that ambush a budget: the permit fee, premium railing, stairs, old-deck removal and disposal, deeper footings on poor or frosty ground, lighting, and skirting. Any one can add hundreds to thousands. Build them in from the start so a “cheap” deck doesn’t balloon.

• Material — the single biggest lever; composite can add 40–60% over pressure-treated.
• Height — a raised deck needs more (and deeper) footings, taller posts, bracing, and 42″ guards.
• Stairs — a full run of code-compliant deck stairs commonly adds $1,500–$3,000.
• Railing — glass, cable, or aluminum cost well above standard wood pickets.
• The lot — poor access, sloped or rocky ground, and deep frost add labour and concrete.
• Demolition — tearing out and disposing of an old deck adds roughly $500–$1,500.

Permits, DIY savings and deposits

How much does the permit and an engineer add?

Permit fees for a residential deck are usually modest — often roughly $150–$400+ depending on the municipality and deck value. An engineer’s stamp only comes in if your design falls outside the prescriptive span tables (long spans, tall decks, a hot tub), and adds a few hundred dollars or more. Most standard decks don’t need one.

See when a stamp is required in the drawings & inspections guide, and the permit thresholds in the Ontario deck permit guide.

How much do I save by doing it myself?

A lot — labour is often 50–60% of the total, so a capable DIYer can save thousands. The trade-offs are your time, tools, and the risk of an inspection redo. Price your DIY materials with the deck building calculator, and get the permit and drawings right first.

What’s a normal contractor deposit?

A normal deposit in Ontario is about 10–30% to book the job and order materials, with the balance tied to milestones. Be wary of anyone demanding full payment up front or a cash-only deal. Put the schedule, deposit, and what each payment covers in the written contract — see hiring a deck builder.

Frequently asked questions