How to price a deck build
Decks look like the simplest job you quote and they are the easiest to lose money on. The visible part — the boards — is a fraction of the work. Most of the cost is under the deck and around its edges.
Every figure below is a 2026 Ontario market range, supplied and installed, before HST.
Why a flat per-square-foot price fails on decks
A useful rule of thumb for a rough range is $40–$60 per square foot in pressure-treated and $70–$100 in composite. Fine for a phone call. Useless for a quote.
The reason is that two 400 square foot decks can differ by $10,000, and none of it is the decking:
- A deck 18 inches off grade needs a handful of footings and no stairs. The same deck at 8 feet needs deeper posts, bracing, guards all round and a full flight
- Railing is priced per linear foot, and a long narrow deck has far more perimeter per square foot than a square one
- Access matters — a wheelbarrow route through a gate is a different job from a backyard you carry everything into
The line items in a deck quote
1. Layout, permit and locates
Drawings for permit run $400–$1,200 for a straightforward residential deck; fees vary by municipality. Utility locates are free but take days — book them before you promise a start date. Your submission and inspection time is a real line.
2. Demolition of the old deck
$8–$16 per square foot including disposal. Old decks with buried footings or sistered ledgers take longer than clients expect.
3. Footings
$250–$450 each for augered sonotube footings poured below frost line. Across most of southern Ontario that means a minimum of four feet. Rock, clay or hand-digging in a tight yard pushes it higher. Helical piles run $350–$600 each and are worth quoting where access is bad.
Footing count is driven by beam span, not deck size — work it out rather than guessing.
4. Framing
Posts, beams, ledger, joists, blocking and hangers: $14–$24 per square foot in pressure-treated. Ledger attachment and flashing to the house is its own line and its own liability — a badly flashed ledger rots the rim joist.
5. Decking surface
Pressure-treated $9–$16 per square foot supplied and installed. Composite $22–$38. Hidden fasteners, picture framing, breaker boards and diagonal patterns all add labour without adding area — price them as extras, not as part of the rate.
6. Railings and guards
The line clients never anticipate. Pressure-treated with square spindles $60–$95 per linear foot; aluminium $110–$170; glass panels higher again. On a small deck the railing can exceed the decking.
7. Stairs
$180–$320 per step including stringers, treads and the landing pad, plus railings on both sides where code requires. A four-step run is a small line; a twelve-step run with a landing is a significant one.
8. Finishing and extras
- Skirting or lattice — $18–$32 per linear foot
- Under-deck storage or grading — priced separately
- Post cap lighting — $60–$120 per post installed
- Staining a new pressure-treated deck — $3–$6 per square foot, and worth telling the client it should wait a season
- Privacy screen — $90–$180 per linear foot
A worked example: a 400 sq ft deck
20×20 attached deck, 3 feet above grade, pressure-treated frame and surface, PT railing on three sides, one four-step run. Ontario, 2026, before HST.
| Stage | Range |
|---|---|
| Drawings, permit coordination, locates | $700–$1,600 |
| Demolition of existing deck | $3,200–$6,400 |
| Footings (9 × sonotube below frost) | $2,250–$4,050 |
| Framing, ledger and flashing | $5,600–$9,600 |
| PT decking surface | $3,600–$6,400 |
| Railing, ~54 linear ft | $3,240–$5,130 |
| Stairs, 4 steps + landing pad | $720–$1,280 |
| Skirting and finishing | $800–$1,900 |
| Project management and supervision | $1,200–$2,200 |
| Typical all-in, before HST | $21,000–$34,000 |
The same deck in composite with aluminium railing runs roughly $34,000–$48,000. Present both — clients who dislike annual staining often choose the higher number themselves.
Ontario code items that get inspected
Not legal advice, and requirements vary by municipality — confirm locally. But these are the ones that fail inspections:
- Footing depth below frost line — four feet minimum across most of southern Ontario
- Guard height and spindle spacing, both specified and both measured
- Ledger attachment — fastener type, spacing and flashing
- Stair rise and run consistency, and graspable handrails
- Permit trigger — generally attached decks, or any walking surface over 24 inches above grade
Where decks lose money
Railing measured as area
The single most common deck quoting error. Railing is linear, and a long narrow deck can have half again the perimeter of a square one at the same square footage.
Footings quoted by guess
Count them off the beam spans. Being two footings short on a quote is $600 out of your margin before you have driven to site.
Access
Every board carried through a house or round a narrow side yard is time. Walk the route before you price the labour.
Weather
Decks are exterior work in a province with weather. Build float into the schedule rather than the price, and say so in the quote — a rained-out week is not a delay you caused.
Quoting one in minutes
Deck quotes are quick to rough out and slow to do properly, because the numbers that matter — perimeter, height, footing count, stair run — all come off the site rather than the plan.
That is what Contrax was built for. Walk the yard with your phone, talking through the layout and heights. The app watches the video, writes the scope, and prices every line off your own rate card. You read it, adjust it, and send it before you have left.
It gives you a draft, not an answer. You check every line before it reaches a client.
Record a yard, drop the clip in, and watch it write the estimate. No signup needed.
See the live demo →Contrax is $150 CAD a month for your whole company — estimating, scheduling, job costing, invoicing and HST-ready books. Built in Oshawa, Ontario.