Deck Board Width: 5/4x6 vs 2x6 — Which Is Better?

You're planning a deck and trying to figure out whether to use 5/4x6 or 2x6 decking boards. The difference matters more than you'd think—it affects your budget, how your deck looks, how long it lasts, and what joist spacing you need.

Here's what you need to know to choose the right board width for your Ontario deck guides.

What Do 5/4x6 and 2x6 Actually Mean?

Neither dimension is what it sounds like. These are nominal sizes—lumber industry labels that don't match the actual finished dimensions.

5/4x6 boards:

• Nominal: 1.25" thick × 6" wide
• Actual finished size: 1" × 5.5"

2x6 boards:

• Nominal: 2" thick × 6" wide
• Actual finished size: 1.5" × 5.5"

Both boards are the same width once milled. The only real difference is thickness: 2x6 boards are 50% thicker than 5/4x6.

That half-inch difference changes everything.

Why 5/4x6 Is the Standard for Most Decks

5/4x6 is the default decking material for residential projects in Ontario. Walk through any neighbourhood in Kitchener, Waterloo, or Cambridge and you'll see it on 90% of decks.

Why it's popular:

• Lighter weight — easier to handle during installation, less strain on your deck's structure
• Lower cost — you're buying less lumber per board
• Perfectly adequate for 16" joist spacing (the standard in residential deck framing)
• Works for all decking types — pressure-treated, cedar, and composite all come in 5/4 profiles

For a typical 200-square-foot deck in KWC, using 5/4x6 pressure-treated boards will cost around $1,200–$1,600 in materials (boards only, not framing). That same deck in composite 5/4x6 runs $2,800–$4,200 depending on brand.

If you're building a standard residential deck with 16" joist spacing and normal foot traffic, 5/4x6 is the right choice. It meets Ontario Building Code requirements, performs well in freeze-thaw cycles, and won't sag or warp under typical loads.

When You Actually Need 2x6 Decking

2x6 boards cost more and weigh more. You only choose them when 5/4x6 isn't strong enough.

Use 2x6 if:

• Joist spacing is 24" — wider spans need thicker boards to prevent bounce and deflection
• Heavy-point loads — hot tub decks, outdoor kitchens, or commercial installations
• Diagonal decking patterns — boards run at 45° angles instead of perpendicular to joists, which increases unsupported span
• You want a more substantial feel — some builders and homeowners prefer the stiffer, less springy surface

A 200-square-foot deck in 2x6 pressure-treated will cost roughly $1,800–$2,400 for boards—about 50% more than 5/4x6. Composite 2x6 runs $4,200–$6,300, a significant jump.

Joist Spacing and Code Compliance

The Ontario Building Code (OBC) allows:

• 5/4x6 boards on joists spaced 16" on center or less
• 2x6 boards on joists spaced 24" on center or less

If you're planning 24" joist spacing to save on framing lumber, you must use 2x6 decking. Using 5/4x6 boards on 24" spans will flex underfoot and fail inspection.

Most residential deck builders in KWC stick with 16" joist spacing and 5/4x6 boards because it's the sweet spot for cost, performance, and code compliance. Read more about framing requirements in our guide to deck joist span tables.

Cost Comparison: 5/4x6 vs 2x6

Prices below are for 2026 KWC market rates, materials only:

| Board Type | 5/4x6 (per linear foot) | 2x6 (per linear foot) |

|------------|-------------------------|----------------------|

| Pressure-treated | $2.50–$3.50 | $3.75–$5.25 |

| Cedar | $4.00–$6.00 | $6.00–$9.00 |

| Composite (mid-tier) | $5.50–$8.00 | $8.00–$12.00 |

| Composite (premium) | $8.00–$11.00 | $12.00–$16.00 |

For a 200 sqft deck, you'll need approximately 360–400 linear feet of decking (depending on board layout and waste).

Total material cost for decking boards:

• 5/4x6 pressure-treated: $900–$1,400
• 2x6 pressure-treated: $1,350–$2,100
• 5/4x6 composite (mid-tier): $2,000–$3,200
• 2x6 composite (mid-tier): $2,900–$4,800

If you're hiring a contractor, expect labour costs of $25–$45/sqft for the full deck build, which includes framing, decking, railings, and stairs. Learn more about pricing in our Kitchener deck cost guide.

Durability and Lifespan

Thickness affects how long your deck lasts, especially with wood.

Pressure-Treated Decking

Both 5/4x6 and 2x6 pressure-treated boards are chemically treated to resist rot and insects. Thicker boards have a slight edge:

• 5/4x6 pressure-treated: 15–20 years with proper maintenance (annual cleaning, sealing every 2–3 years)
• 2x6 pressure-treated: 20–25 years — more wood mass means more chemical penetration and longer service life

In Ontario's freeze-thaw climate, both thicknesses handle moisture cycling well if you maintain proper deck board spacing (3/16" gap for PT lumber) and keep up with staining/sealing.

Cedar Decking

Cedar naturally resists rot without chemical treatment. Thickness matters here too:

• 5/4x6 cedar: 20–30 years with minimal maintenance
• 2x6 cedar: 25–35 years — thicker boards weather more slowly

Cedar grays over time unless you apply UV protectant annually. Both thicknesses perform the same in terms of surface weathering, but 2x6 boards wear down more slowly from foot traffic.

Composite Decking

Composite boards (wood fiber + plastic) don't rot, splinter, or need sealing. Thickness affects stiffness, not lifespan:

• 5/4x6 composite: 25–30 years (manufacturer warranty typically 25 years)
• 2x6 composite: 25–30 years (same warranty)

The performance difference is minimal. Premium composite brands like Trex offer the same warranty regardless of board thickness. You're paying extra for rigidity, not longevity.

For more on composite options, see our complete guide to composite decking in Canada.

Installation Differences

Weight and Handling

• 5/4x6 board (12 ft pressure-treated): ~18 lbs
• 2x6 board (12 ft pressure-treated): ~27 lbs

If you're doing the work yourself, 5/4x6 is noticeably easier to maneuver, especially on second-story decks or tight jobsites.

Fastener Requirements

Both thicknesses use the same fasteners:

• Screws: #10 × 3" stainless steel or coated deck screws (2 per joist per board)
• Hidden fasteners: Compatible with both thicknesses (check manufacturer specs)

Thicker 2x6 boards grip screws better and resist pull-through slightly more, but it's not a major factor. Most deck failures come from framing issues, not decking pull-out.

Cutting and Waste

Thicker boards take longer to cut and dull saw blades faster. The difference is small, but over a full deck, 2x6 adds 10–15% more labour time compared to 5/4x6.

Surface Feel and Aesthetics

5/4x6 boards have a slight spring when you walk on them with 16" joist spacing. Most people don't notice, but if you're sensitive to flex, it might bother you.

2x6 boards feel more solid underfoot. The extra stiffness eliminates bounce entirely, even with 24" joist spacing. Some homeowners and builders prefer the "premium" feel.

Visually, you can't tell the difference once the deck is finished. Both boards are 5.5" wide, so the surface pattern looks identical.

What About Composite Board Widths?

Composite decking comes in both 5/4x6 and 2x6 profiles, but also in wider plank formats:

• Standard composite: 5/4x6 (same as wood sizing)
• Wide-plank composite: 5/4x8, 5/4x12 (less common, fewer seams)

Most composite manufacturers recommend 16" joist spacing for 5/4 boards, regardless of width. If you want 24" spacing, you'll need 2x6 composite or special support clips.

Premium brands like Trex and other top composite options offer both thicknesses. The pricing gap is similar to wood—2x6 costs about 50% more than 5/4.

For maintenance expectations, read our guide on composite deck care in Ontario.

Which Should You Choose?

Go with 5/4x6 if:

• Your joists are spaced 16" on center
• You're building a standard residential deck
• You want to save 30–50% on decking material costs
• You're using pressure-treated or cedar and maintaining it regularly

Go with 2x6 if:

• Your joists are spaced 24" on center
• You're installing a hot tub or heavy outdoor furniture
• You're running boards diagonally (45° pattern)
• You prefer a stiffer, more solid-feeling deck
• You're building a commercial deck with higher load requirements

For most Ontario homeowners in Kitchener, Waterloo, and Cambridge, 5/4x6 on 16" joists is the right call. It meets code, performs well in our climate, and costs significantly less.

If your project has unusual structural demands or you're willing to pay extra for a premium feel, 2x6 makes sense. But don't overspend on thicker boards unless your framing actually requires them.

Common Questions

Can I use 5/4x6 boards on 24-inch joist spacing?

No. The Ontario Building Code requires 2x6 minimum thickness for joists spaced 24" on center. Using 5/4x6 boards on that span will cause excessive deflection and won't pass inspection. Stick with 16" spacing if you want to use 5/4x6.

Do 2x6 boards last longer than 5/4x6?

For pressure-treated and cedar, yes—thicker boards have more material to weather and erode, so they last 3–5 years longer on average. For composite decking, no—both thicknesses have the same lifespan and warranty (25–30 years). You're paying for stiffness, not durability.

Which thickness do deck builders in KWC typically use?

5/4x6 on 16" joist spacing is standard for 95% of residential decks in Kitchener-Waterloo-Cambridge. Builders use 2x6 only when joist spacing is 24", when diagonal decking is specified, or when a homeowner requests it for a stiffer feel. See our deck builder contract checklist for what to ask your contractor.

Will 5/4x6 boards sag or warp over time?

On 16" joist spacing, no—5/4x6 boards are structurally sound and won't sag under normal residential loads. Warping depends on wood quality and moisture, not thickness. Make sure your contractor uses joist tape to prevent rot at contact points. Read more in our guide on deck joist tape and membrane.

Can I mix 5/4x6 and 2x6 on the same deck?

Technically yes, but it creates a 1/2" height difference between boards, which looks terrible and creates a trip hazard. Don't do it. Pick one thickness and stick with it across the entire deck surface. If you're doing a deck border or picture frame, use the same thickness for a clean finish.