Guide · § Deck cost by size · 2026

What every common deck size actually costs in 2026

Eight canonical deck sizes — from 8 × 8 up to 20 × 20 — priced through the same calculator the rest of the site uses. No fabricated numbers, no aggregated “average per square foot” rates that fall apart in practice. Just the calculator run eight times at each material.

All figures CAD, before HST. Each build assumes 2–4′ off grade, aluminum railing on three sides, a 3-step run to grade, no demolition, and a typical GTA permit included. Toggle the calculator to model your specific build.

§ I.The size × material grid

Installed cost: every size in every material

The single most-asked question in our inbox is “what would a [size] deck cost in [material]”. Here’s the answer for the eight most common sizes × four materials — thirty-two numbers, all computed by the same function.

Installed cost of common deck sizes by material, computed by the site calculator.
Size	Pressure-treated	Cedar	Composite	PVC
8 × 864 sq ft	$6,700 – $9,900$105/sq ft – $155/sq ft	$6,700 – $9,900$105/sq ft – $155/sq ft	$6,700 – $10,150$105/sq ft – $159/sq ft	$7,050 – $12,000$110/sq ft – $188/sq ft
10 × 10100 sq ft	$7,100 – $10,550$71/sq ft – $106/sq ft	$7,450 – $12,050$75/sq ft – $120/sq ft	$8,550 – $14,350$86/sq ft – $143/sq ft	$10,150 – $17,200$102/sq ft – $172/sq ft
10 × 12120 sq ft	$7,250 – $11,000$60/sq ft – $92/sq ft	$8,600 – $13,750$72/sq ft – $115/sq ft	$9,900 – $16,500$82/sq ft – $138/sq ft	$11,800 – $19,950$99/sq ft – $166/sq ft
12 × 12144 sq ft	$7,700 – $12,700$53/sq ft – $88/sq ft	$10,050 – $16,000$70/sq ft – $111/sq ft	$11,600 – $19,300$80/sq ft – $134/sq ft	$13,900 – $23,450$97/sq ft – $163/sq ft
12 × 16192 sq ft	$9,550 – $15,600$50/sq ft – $81/sq ft	$12,650 – $20,000$66/sq ft – $104/sq ft	$14,700 – $24,450$77/sq ft – $127/sq ft	$17,850 – $29,950$93/sq ft – $156/sq ft
14 × 16224 sq ft	$11,000 – $17,900$49/sq ft – $80/sq ft	$14,600 – $23,050$65/sq ft – $103/sq ft	$17,050 – $28,250$76/sq ft – $126/sq ft	$20,650 – $34,650$92/sq ft – $155/sq ft
16 × 20320 sq ft	$14,500 – $23,550$45/sq ft – $74/sq ft	$19,700 – $30,900$62/sq ft – $97/sq ft	$23,150 – $38,250$72/sq ft – $120/sq ft	$28,350 – $47,450$89/sq ft – $148/sq ft
20 × 20400 sq ft	$17,650 – $28,550$44/sq ft – $71/sq ft	$24,150 – $37,750$60/sq ft – $94/sq ft	$28,450 – $46,950$71/sq ft – $117/sq ft	$34,950 – $58,450$87/sq ft – $146/sq ft

Every row is the calculator run four times for that size, once per material, at the standard GTA assumptions described above. Per-sq-ft rate falls as size rises because the minimum-project floor and fixed costs amortize over more area.

§ II. Size by size

What each size is actually for

The number from the calculator is half the answer. The other half is what kind of deck you actually end up with at that footprint — how many people it seats, whether it triggers coverage bylaws, what permit cycle it’s on, where it makes architectural sense.

8 × 8 (64 sq ft) — the smallest legal deck

At 64 square feet the minimum-project floor dominates the calculation. The contractor still has to mobilize a crew, deliver lumber, set footings, and pull a permit; spreading those fixed costs over 64 sq ft pushes the per-sq-ft rate above what you'll see quoted on a larger deck. Most builders won't even quote a deck this small as a standalone job — it gets bundled with other work or quoted at a flat minimum.

When it fits: Basement walkouts, small balcony replacements, BBQ landing pads off a side door. Anywhere you need a flat surface but the lot or layout won't support more.

Pressure-treated: $6,700 – $9,900
Composite: $6,700 – $10,150

10 × 10 (100 sq ft) — the starter deck

The smallest size most GTA contractors will quote without a minimum-project surcharge. A 10 × 10 fits a four-seat bistro table or a small lounge chair pair, and clears coverage bylaws in essentially every GTA municipality without variance. The per-sq-ft rate is still high because fixed costs are spread thin; if your budget supports going to 12 × 12, the per-sq-ft drops noticeably and you get 44% more usable area.

When it fits: Coffee-deck off the kitchen, small backyard for an apartment-style home, condo townhouse rear deck.

Pressure-treated: $7,100 – $10,550
Composite: $8,550 – $14,350

10 × 12 (120 sq ft) — the most common 'starter' rectangle

10 × 12 is the size the cost-breakdown guide chapter calls the 'small reference build' — common enough to be its own price point, big enough to seat six comfortably. Under 24″ off grade it doesn't need a railing in most GTA cities, which knocks $1,500–$2,500 off the typical quote.

When it fits: Standard suburban first-deck, second-floor balcony replacement, garden-suite backyard deck.

Pressure-treated: $7,250 – $11,000
Composite: $9,900 – $16,500

12 × 12 (144 sq ft) — the suburban default

The single most-quoted deck size in the GTA. A 12 × 12 fits a six-seat table with seating room on three sides, leaves space for a couple of planters, and reads as a real outdoor room rather than a landing. Composite economics start to make sense at this size because the material premium is amortized over more square footage.

When it fits: Standard backyard for a detached suburban home, family-of-four primary deck.

Pressure-treated: $7,700 – $12,700
Composite: $11,600 – $19,300

12 × 16 (192 sq ft) — the GTA sweet spot

12 × 16 is the most popular larger deck size in 2026 because it allows a clear split between dining (six-seat table at one end) and lounging (couch or chair pair at the other) without becoming a maintenance burden. Most municipalities will permit it without variance on a standard residential lot. The per-sq-ft rate drops noticeably below the smaller sizes because the labour-to-area ratio improves.

When it fits: Families who want dedicated dining + lounging zones, homes that entertain regularly, primary deck for a 4–6 person household.

Pressure-treated: $9,550 – $15,600
Composite: $14,700 – $24,450

14 × 16 (224 sq ft) — the next-tier upgrade

14 × 16 is what people upgrade to when 12 × 16 starts feeling tight — usually after a year or two of regular hosting. It's the size we use for the reference cedar-vs-composite five-year cost comparison because it's representative of the upper end of suburban first-deck builds. Coverage bylaws start to bind in some municipalities at this size; check the per-city page for your municipality.

When it fits: Active hosts, families with multiple seating zones, homes where the deck is the primary outdoor room.

Pressure-treated: $11,000 – $17,900
Composite: $17,050 – $28,250

16 × 20 (320 sq ft) — premium suburban

16 × 20 starts to feel like an extension of the house. Two clearly-separated zones (typical layout: dining + outdoor sofa + side-table cluster), often with a built-in bench along one edge. Coverage bylaws will frequently require variance approval at this size on smaller suburban lots; the permit cycle adds 2–6 weeks. Most municipalities require engineered footings if any part of the deck is more than 24″ off grade.

When it fits: Larger Vaughan / Markham / Oakville / Burlington lots, homes that host 8–12 regularly, designers' clients who want the deck to read as a major architectural element.

Pressure-treated: $14,500 – $23,550
Composite: $23,150 – $38,250

20 × 20 (400 sq ft) — entertaining-scale

At 400 sq ft you're at the upper edge of what most municipalities will permit on a residential lot without variance, and at the upper edge of what a single deck-builder crew will handle as a standalone job. Above 20 × 20, most projects get broken into multiple levels or get treated as outdoor-living renovations (pergola + outdoor kitchen + deck combined) rather than as deck builds. Plan for an engineered design, a longer permit cycle, and a real conversation with the contractor about phasing.

When it fits: Estate-scale lots, multi-generational families, homes where the deck is the entertaining centrepiece, replacement of an older multi-level deck with a single-level larger one.

Pressure-treated: $17,650 – $28,550
Composite: $28,450 – $46,950

§ III. Local defaults

What 12 × 16 costs in each GTA municipality

Each city has a different dominant material in new 2026 builds. Below is the same 12 × 16 deck priced through whichever material is the local default — useful for grounding what a “typical” quote in your municipality should land at.

Cost of a 12 × 16 deck in each GTA city, priced through the locally-typical material.
City	Local default	12 × 16 installed
Toronto	Composite (Trex-tier)	$14,700 – $24,450
Mississauga	Composite (Trex-tier)	$14,700 – $24,450
Brampton	Pressure-treated lumber	$9,550 – $15,600
Hamilton	Pressure-treated lumber	$9,550 – $15,600
Vaughan	Composite (Trex-tier)	$14,700 – $24,450
Markham	Composite (Trex-tier)	$14,700 – $24,450
Oakville	Composite (Trex-tier)	$14,700 – $24,450
Burlington	Composite (Trex-tier)	$14,700 – $24,450
Richmond Hill	Composite (Trex-tier)	$14,700 – $24,450
Oshawa	Pressure-treated lumber	$9,550 – $15,600
Milton	Composite (Trex-tier)	$14,700 – $24,450
Ajax	Pressure-treated lumber	$9,550 – $15,600
Pickering	Composite (Trex-tier)	$14,700 – $24,450
Whitby	Composite (Trex-tier)	$14,700 – $24,450
Guelph	Composite (Trex-tier)	$14,700 – $24,450

Each city page has the same calculator pre-loaded with the local default material, plus a full per-city size table for that municipality — click through to your city to see the breakdown for your specific build.

§ IV. Related

Keep reading

Chapter I