Introduction
A roof truss looks like simple lumber nailed into triangles, but every component is specified: the lumber species and grade, the size and placement of the steel gusset plates, the sheathing grade and thickness, and the connectors that tie the whole assembly to the walls. Understanding the materials does two practical things — it lets you read a truss quote intelligently, and it keeps you from substituting the wrong product at the lumber yard.
The Roof Truss Calculator tells you how many trusses and how much sheathing your roof needs; this guide covers what those pieces are made of, which grades and products suit which jobs, and the quantities to estimate. For the full purchase list, see the estimating guide.
Truss Lumber: Species and Grades
Truss plants build with stress-graded dimensional lumber — most commonly SPF (spruce-pine-fir) and SYP (southern yellow pine) in North America, or graded softwood (typically C16/C24 in Europe) elsewhere. The grade stamp on each board certifies its strength; the truss design software assigns each member the minimum grade it needs.
- 2×4 (38×89 mm) — standard for chords and webs on typical residential spans at 24 in o.c.
- 2×6 (38×140 mm) — used for bottom chords carrying ceiling loads, longer spans, or heavy snow designs.
- 2×8 and larger — top chords on long spans, girder truss plies, and high-load designs.
You don’t choose these sizes — the manufacturer’s engineering does. What you can check on delivery is that the grade stamps on the lumber match the species and grade shown on the engineering drawings. A substituted lower grade is a rejected delivery.
Gusset Plates and Connectors
Metal connector plates
The toothed steel plates pressed into each truss joint at the factory are what make a truss a truss — they transfer loads between members without bolts or nails. They’re sized and positioned by the engineering software; plate size grows with the forces at the joint. These plates are factory-pressed with hydraulic equipment and can’t be replicated on site, which is one reason field repairs need manufacturer approval.
Truss-to-wall connectors
Where the truss meets the wall plate, the connection resists both downward load and wind uplift. Common hardware:
- Hurricane ties/straps — metal connectors nailed to both truss and plate, rated for a specified uplift force (e.g., 500–1500+ lbs / 2–7 kN depending on the model). Required by code in high-wind regions and good practice everywhere.
- Truss clips — lighter-duty connectors for low-wind zones, allowing slight truss movement while holding alignment.
- Specified nailing — the drawings call out nail quantity, size, and placement per heel joint (e.g., “3-16d nails each side”). The uplift rating assumes exactly this fastening.
Bracing lumber
Both temporary installation bracing and the permanent lateral bracing on the drawings are ordinary 2×4 lumber — but “ordinary” still means straight, and permanent bracing should be the grade the drawings specify. Budget a dozen or more 2×4s for a typical house; the pro tips guide sequences their installation.
Sheathing: OSB vs. Plywood
Roof sheathing is structural — it forms the diaphragm that ties trusses together and carries wind loads to the walls. The two options:
| Property | OSB | Plywood |
|---|---|---|
| Typical roof thickness | 7/16 in (11 mm) | 15/32 in (12 mm) |
| Panel size | 4×8 ft (1220×2440 mm) | 4×8 ft (1220×2440 mm) |
| Cost | Lower — the commodity choice | Higher, roughly 15–30% more |
| Moisture behavior | Swells at edges if soaked; recovers slowly | More forgiving of wetting during construction |
| Span rating | Check the APA stamp (e.g., 24/16) | Check the APA stamp (e.g., 32/16) |
The span rating stamp is what matters: a “24/16” panel is rated for 24-in roof spans. Match the rating to your truss spacing — 24-in o.c. trusses need sheathing rated for 24-in spans. Heavier roofing (tile, slate) or high snow loads may push the design to thicker sheathing or tighter spacing.
Underlayment and Fasteners
Underlayment
Between sheathing and roofing goes the water-shedding layer: asphalt-saturated felt (15-lb or 30-lb) or synthetic underlayment. Synthetic is lighter, stronger, and lays flatter; felt is cheaper. Ice-and-water shield (self-adhering membrane) goes at eaves, valleys, and penetrations in cold climates — code requires it where ice dams form.
Fasteners
- Sheathing nails — 8d common or ring-shank, spaced per code (typically 6 in at panel edges, 12 in in the field; tighter in high-wind zones). Ring-shank nails hold dramatically better against uplift.
- Truss nails — as specified on the drawings for heel connections; don’t substitute shorter or thinner nails.
- Quantity rule of thumb — roughly 2–3 lbs of sheathing nails per sheet (1–1.5 kg), so 44 sheets ≈ 90–130 lbs (40–60 kg). The estimating guide includes the full fastener takeoff.
Ridge Board and Stick-Framing Lumber
For the stick-framed sections (porches, dormers, additions), the material list differs:
- Ridge board — 1 in (25 mm) thick, at least as deep as the rafter (2×8 ridge for 2×8 rafters typical); length = building length plus gable overhangs. A structural ridge beam is a different, engineered member.
- Rafters — sized by span and load per code span tables: 2×6 for short spans, 2×8/2×10/2×12 as span and snow load grow. The calculator’s rafter length (e.g., 13.42 ft for a 24 ft span at 6/12) sets the board length to buy — 14 ft stock for a 13.42 ft rafter.
- Ceiling joists / rafter ties — resist the outward thrust of rafters; sized and spaced per code, typically matching the rafter spacing.
Material Quantity Reference
For a 30 × 40 ft gable roof, 24 in o.c., 6/12 pitch (truss count 21 + 2 gable ends, slope 15.66 ft with overhang):
| Material | Quantity | Notes |
|---|---|---|
| Common trusses | 21 | Per manufacturer engineering |
| Gable-end trusses | 2 | Confirm included in quote |
| Sheathing (4×8) | 44 sheets | 7/16 in OSB 24/16 rated + 10% waste |
| Hurricane ties | 46+ | One per truss bearing (2 per truss) |
| Bracing 2×4 | 12–16 pcs | Temporary + permanent |
| Sheathing nails | ~100 lbs (45 kg) | 8d ring-shank |
| Underlayment | ~14 squares | Roof area 1253 ft² ÷ 100 + waste |
Metric equivalent: 9.14 × 12.19 m roof, 600 mm o.c. — 21 + 2 trusses, 44 sheets of 1220×2440 mm, ~45 kg nails, ~116 m² underlayment. The cost guide prices this list.
Related Guides
- Estimating Guide — turn this material list into a purchase order.
- Cost Guide — what each material costs, installed.
- Complete Guide — truss types, spacing, loads, worked examples.
- Pro Tips — handling, storage, and setting-day sequencing.
- Ordering & Install Checklist — verify materials on delivery day.
Get Your Number
Materials are where a truss project is won or lost: the right lumber grades, connector plates pressed at the factory, sheathing rated for your spacing, and the exact fasteners the drawings specify — no substitutions at the bearing connections. Start with quantities from the Roof Truss Calculator, build the list with this guide, and check every delivery against the engineering drawings before anything goes up.
Disclaimer: Calculator results are planning estimates based on the dimensions you enter. Roof trusses are engineered structural products — always order from a manufacturer that supplies sealed engineering drawings, verify spans and loads with a licensed engineer, and check your local building code before construction.
