16 vs 24 On-Centre SpacingComplete Guide
Everything you need to know about choosing between 16-inch (400 mm) and 24-inch (600 mm) on-centre spacing for wall studs, floor joists, ceiling joists, and roof rafters.
Quick Answer
Use 16" (400 mm) on-centre (OC) spacing for load-bearing walls, most floor joists, and any application where maximum structural strength is required. Use 24" (600 mm) OC spacing for non-load-bearing interior partition walls, some roof trusses, and situations where code allows it and you want to reduce material costs by up to 33%.
What Is On-Centre Spacing?
On-centre (OC) spacing is the distance measured from the centre of one framing member to the centre of the next. This is the standard way builders and building codes specify the spacing of studs, joists, rafters, and trusses in wood-frame construction.
The two most common on-centre spacing measurements in residential construction are 16 inches (400 mm) and 24 inches (600 mm). The choice between these two spacings affects structural capacity, material cost, insulation performance, and compatibility with standard building materials. In Canada, both imperial and metric measurements are used on job sites.
Standard building materials like 4×8-foot plywood, OSB sheets, and drywall panels are manufactured in dimensions divisible by both 16 and 24 inches (400 mm and 600 mm), so panel edges always land on a framing member at either spacing.
16" OC vs 24" OC: Side-by-Side Comparison
How the two most common framing spacings compare across every major application.
| Application | 16" (400 mm) On-Centre | 24" (600 mm) On-Centre |
|---|---|---|
| Exterior Load-Bearing Walls | Required by most codes for 2×4 walls. Strongest option. | Allowed with 2×6 studs in some jurisdictions (check local code). |
| Interior Non-Load-Bearing Walls | Common but not required. More fastening points for cabinets. | Code-compliant. Saves ~33% on stud material. |
| Floor Joists (2×10, typical span) | Spans up to ~4.9 m (16 ft) with SPF #2. Stiffer floor. | Spans up to ~4.0 m (13 ft) with same lumber. May feel bouncy. |
| Ceiling Joists (non-attic storage) | Standard for attic storage. Supports drywall plus loads. | Adequate for drywall-only ceilings with no attic storage. |
| Roof Rafters / Trusses | Used in high snow-load areas (>1.9 kPa / 40 psf ground snow load). | Standard for engineered trusses in moderate climate zones. |
| Material Cost (per linear foot of wall) | ~$5.00–$7.00 CAD/ft (more lumber, more fasteners). | ~$3.50–$5.00 CAD/ft (fewer studs, less labour). |
| Insulation | Standard R-13 to R-15 batts for 2×4, R-19 to R-21 for 2×6. | Wider bays allow R-21+ for 2×6 walls. Better thermal performance. |
| Drywall Support | Excellent fastening. Less risk of nail pops and sagging. | Requires 5/8" (15.9 mm) drywall on ceilings to prevent sag. |
When to Use 16" (400 mm) On-Centre Spacing
16-inch on-centre spacing is the more conservative and commonly used option. Here is when it is required or strongly recommended:
- Load-bearing exterior walls — Required by the NBC (National Building Code of Canada) for most 2×4 wall assemblies carrying roof and floor loads.
- Floor joists for longer spans — 16" OC allows joists to span greater distances. For a 2×10 SPF #2 joist, 16" OC spans up to 4.9 m (16’2″) vs only 4.0 m (13’1″) at 24" OC.
- Areas supporting heavy finishes — Tile floors, stone countertops, or built-in cabinetry benefit from the extra support that 16" OC framing provides.
- High wind or seismic zones — Building codes in high-wind and seismic zones (such as coastal British Columbia) often mandate 16" OC (or closer) for shear wall construction.
- Ceiling joists with attic storage — If the attic will be used for storage or future living space, 16" OC provides the necessary load capacity.
- Walls with heavy cladding — Brick veneer, stucco over OSB, and fibre cement siding all perform better with studs at 16" OC.
Bottom line: when in doubt, 16" OC (400 mm) is the safer choice. The extra material cost is modest compared to the structural benefits.
When to Use 24" (600 mm) On-Centre Spacing
24-inch on-centre spacing uses fewer framing members and can save significant material and labour costs. Here is when it is appropriate:
- Non-load-bearing interior partition walls — The NBC allows 24" OC for interior walls that carry no structural load. This is the most common application.
- Engineered roof trusses — Most manufactured trusses are designed for 24" (600 mm) OC spacing. The truss engineering accounts for the wider spacing.
- Advanced framing (OVE) construction — Optimum Value Engineering uses 2×6 studs at 24" OC with single top plates, reducing lumber by up to 30% while improving insulation — especially valuable in Canada’s cold climate to achieve higher effective R-values.
- Gable end walls — Non-structural gable end walls above the roof line can typically use 24" OC spacing.
- Ceiling joists (drywall only) — Where the ceiling only supports drywall with no attic storage above, 24" OC is code-compliant.
- Budget-conscious projects — On a 2,000 sq ft home, switching non-load-bearing walls to 24" OC can save $1,100–$1,700 CAD in lumber alone.
Bottom line: 24" OC (600 mm) is a smart choice where code allows it, especially for non-load-bearing walls and engineered trusses.
Building Code Requirements (NBC)
The National Building Code of Canada (NBC) provides specific guidance on when each spacing is permitted. Here are the key code sections:
- NBC 9.23.3 — Exterior load-bearing walls: 2×4 studs at 400 mm (16") OC or 2×6 studs at 600 mm (24") OC (with approved sheathing).
- NBC 9.23.3 — Interior non-load-bearing partitions: 2×4 or 2×3 studs at 600 mm (24") OC maximum.
- NBC 9.23.4 — Floor joist spans: Tables specify maximum spans for each species, grade, and spacing (300 mm, 400 mm, 500 mm, 600 mm).
- NBC 9.23.4 — Rafter spans: Similar span tables for roof rafters at various spacings.
- NBC 9.29 — Drywall application: 12.7 mm (1/2") drywall on walls at up to 600 mm OC; 15.9 mm (5/8") drywall required on ceilings at 600 mm OC.
- Provincial amendments may override NBC defaults. Always check with your local building department before finalising framing plans. Ontario (OBC), British Columbia (BCBC), Alberta (ABC), and Quebec (CCQ) each maintain their own building code editions.
Important: Building codes are minimum standards. Your engineer or local building department may require closer spacing based on site-specific conditions like soil type, wind exposure, or snow load — particularly important in Canada’s northern and mountainous regions.
Cost Comparison: 16" vs 24" On-Centre
Material savings is one of the biggest reasons builders consider 24" OC spacing. Here is how the numbers break down:
For a standard 8-foot wall, 16" OC spacing requires one stud every 16 inches — roughly 0.75 studs per linear foot of wall. At 24" OC, you need about 0.50 studs per linear foot. That is a 33% reduction in stud count.
On a typical 2,000 sq ft single-storey home with ~200 linear feet of interior partitions, switching from 16" to 24" OC saves approximately 50 studs. At $8–$11 CAD per stud (2024 pricing for 2×4×96 SPF from Home Hardware or RONA), that is $400–$550 CAD in studs alone. Factor in reduced fasteners, reduced labour (fewer studs to cut, carry, and nail), and the savings reach $1,100–$1,700 CAD.
However, do not use 24" OC spacing just to save money on load-bearing walls. The cost of a structural failure or code violation far exceeds any material savings. The savings apply only where 24" OC is code-compliant.
Impact on Other Materials
Your framing spacing does not just affect lumber. It has a ripple effect across multiple building systems:
Insulation
Fiberglass batts come in widths designed for both 16" (400 mm) and 24" (600 mm) OC bays. At 16" OC, standard batts are 15 inches wide (R-13 or R-15 for 2×4 walls). At 24" OC, batts are 23 inches wide. The wider bays at 24" OC actually improve thermal performance because there are fewer studs acting as thermal bridges — critical in Canada where heating degree days range from 3,500 to over 9,000. In advanced framing, 2×6 studs at 24" OC can achieve R-21 wall assemblies with standard batts.
Drywall
Standard 12.7 mm (1/2-inch) drywall works well on walls at either 16" or 24" OC. However, on ceilings, the NBC requires 15.9 mm (5/8-inch) drywall when joists or trusses are spaced at 600 mm (24") OC to prevent sagging. 15.9 mm drywall costs about 20–30% more per sheet than 12.7 mm, which partially offsets the framing savings.
Sheathing and Siding
4×8 plywood and OSB panels work at both spacings since their edges land on framing members. However, at 24" OC, the panel spans a greater unsupported distance between studs. For structural sheathing (like wall bracing), verify the panel rating matches the stud spacing per CSA O325. Panels rated for 600 mm OC are required when using 24-inch spacing on structural sheathing applications.
Calculate Your Materials
Use our free calculators to get exact material quantities for your project at either 16" (400 mm) or 24" (600 mm) on-centre spacing: