Roof Truss Calculator (Canada)
Free Canadian roof truss calculator. Size prefab trusses to NBC 2020, CSA O86 and TPIC 2014. Member lengths, count and delivered cost in CAD across ON, BC, AB, QC.
Roof Truss Calculator
Estimate truss member lengths, the number of trusses needed for your building, total lumber, and a delivered prefab cost.
Slope factor used: 1.118. Lumber LF is the linear sum of all chords and webs per truss, useful for comparing site-built vs prefab. Add 5–10% for cuts and connectors.
Roof truss calculator — Canadian builds
This tool sizes prefabricated roof trusses for Canadian housing and small commercial buildings to TPIC 2014 and CSA O86-22, with NBC 2020 reference for snow and wind. Set your span, pitch in X/12 and truss centres to get:
- Top chord (rafter) length per side
- Bottom chord length
- Web member total by truss type — Fink, mono-pitch, attic, scissor, queen
- Truss count based on building length and spacing
- Total lumber linear footage
- Per-truss and total delivered cost in CAD
The Canadian construction industry runs in mixed units — feet/inches for framing dimensions, metric for structural design — so this calculator accepts feet for span and inches for spacing, like every Canadian truss order form.
How the math works
Canadian prefab trusses are triangulated S-P-F (Spruce-Pine-Fir) #2 and Better assemblies pressed with metal connector plates designed to TPIC 2014 Truss Design Procedures and Specifications. The geometry is span × pitch × depth.
Top chord. For a symmetric duo-pitch Fink:
slopeFactor = √(1 + (rise/run)²)
topChord = (span / 2) × slopeFactorFor a 30 ft span at 6/12 pitch, topChord = 15 × 1.118 = 16.77 ft per side. The yard orders 18 ft S-P-F 2x6 #2 and trims on the docking saw before plate-pressing.
Bottom chord. Equal to the span plus a 2” bearing allowance each end. One-piece up to 32 ft, then a finger-joint or two-piece splice with a hardware plate above an internal bearing wall.
Webs. Type-dependent — Fink ≈ 0.62 × span, king-post ≈ 0.30 × span, scissor ≈ 0.70 × span, attic ≈ 1.10 × span.
Truss count. Count = ceil(building length ÷ spacing) + 1. A 40 ft long house at 24” OC needs 21 trusses.
Truss types — when to specify which
| Type | Best for | Span limit | Cost vs Fink |
|---|---|---|---|
| Fink (W-truss) | Single-family detached, semi | 32 ft | 1.00× |
| King post | Garages, sheds, additions | 16 ft | 0.75× |
| Queen post | Storage barns, simple cottages | 24 ft | 0.85× |
| Howe / Pratt | Long-span agricultural, light commercial | 60 ft | 1.10× |
| Scissor | Vaulted living rooms (cathedral effect) | 30 ft | 1.30× |
| Attic / room-in-roof | Conditioned attic / loft conversions | 28 ft | 1.85× |
| Mono-pitch | Lean-to additions, carports | 16 ft | 0.80× |
For long-span Howe trusses (warehouses, hangars), expect a custom-engineered quote rather than typical-pricing.
Canadian pricing — 2026 reference data
S-P-F lumber has averaged CA$520/MBF for 2x6 #2 KD through Q1 2026, with the Random Lengths Western S-P-F composite stable since the 2024 supply rebound. Delivered prefab Fink trusses on a 50 mile radius are quoting CA$5.00–CA$7.50 per linear foot of span for residential 4/12–8/12 pitches at NBC roof loads up to 2.0 kPa snow.
Worked example (the calculator’s reference test): a 30 ft span × 40 ft long single-family detached at 6/12 pitch, 24” OC, Toronto (Ss 1.5 kPa, Sr 0.4 kPa):
- 21 Fink trusses at CA$5.50/lf × 30 ft span = CA$165 each → CA$3,470 truss order
- Delivery: included for orders above 15 trusses within 50 mi
- Crane and 3-person crew on set day: CA$900–CA$1,400
- Total prefab roof structure: CA$4,400–CA$4,900
By comparison, a cut roof using site-cut S-P-F 2x6 rafters and a doubled 2x10 LVL ridge runs CA$1,900 in lumber + CA$2,400 in framers’ labour (16 hrs × 2 carpenters at CA$72/hr) = CA$4,300. Material cost is similar; trusses save 10–14 hours of programme and avoid the LVL ridge engineering.
NBC and Canadian code
- NBC 2020 9.23.13 — Roof framing. Sets requirements for trussed rafters in Part 9 housing.
- NBC 2020 9.26.4.4 — Ice and water shield. Required at eaves on every Canadian house; the heel height must leave room for it plus insulation and ventilation.
- NBC 2020 9.19.1 — Roof spaces ventilation. 1:300 ratio, distributed top and bottom; the 25 mm continuous airway requirement.
- CSA O86-22 — Engineering design in wood. Structural design code the truss manufacturer’s P.Eng. seals to.
- TPIC 2014 — Truss Design Procedures and Specifications for Light Metal Plate Connected Wood Trusses. The product/design standard for Canadian trussed rafters; SBCAC member yards comply.
- NBC Appendix C — Climatic data per municipality. Snow Ss/Sr, wind Vh, design temperatures.
- OBC 9.23 / BCBC 9.23 / CCQ 9.23 — Provincial code adoptions; mostly aligned with NBC, with provincial deviations.
Buying tips
- Three SBCAC quotes — sbcac.ca member directory. Pricing varies 10–15% on the same lumber feedstock.
- Specify Ss/Sr by municipality — never just “standard residential.” NBC Appendix C is the source of truth.
- Energy heel for R-50 attic — a 12” heel keeps R-50 insulation continuous over the wall plate with the 25 mm airway. Standard 4–6” heels force a thermal-bridge compromise.
- Order to OBC / BCBC permit drawings — provincial permit officers want the truss design pack referenced to NBC 2020 + the provincial overlay before the framing inspection.
- Schedule the crane — a 30 ft span × 21 truss set at 24” OC needs a 14-ton boom truck for a half day, CA$900–CA$1,400 across most of Canada.
Pair with these calculators
- Roof pitch calculator — convert between rise/run, degrees and slope factor.
- Roof rafter calculator — sizes individual rafters with NBC dead + live load checks.
- Roof replacement calculator — full re-roof, including ice and water shield and shingle replacement to Canadian climate zones.
Outputs update as you change inputs. Print the result and pass it to an SBCAC-member yard for a comparable quote.