About Roof Truss Design and Material Calculation
The roof truss design calculator helps estimate truss quantity, lumber requirement, and overall material cost for pitched roof structures. It supports both wood and steel trusses used in modern residential and industrial buildings.
Formulas Used:
- Rise = (Span / 2) × tan(Pitch Angle)
- Rafter Length = √((Span/2)² + Rise²)
- Truss Count = (Building Length / Spacing) + 1
- Lumber Length per Truss = 2 × Rafter + Span
- Total Roof Area = 2 × (Rafter Length × Building Length)
- Total Cost = Roof Area × Cost × (1 + Wastage/100)
Example:
For a span of 10m, pitch of 25°, building length of 20m, spacing of 2m, and cost ₹700/m²:
Rise = 2.33m, Rafter = 5.59m
Trusses = 11, Roof Area = 223.6 m²
Total Cost ≈ ₹164,000 (including 5% wastage)
Material Selection Tips:
- Use wood trusses for small residential spans (≤ 12m).
- Use steel trusses for large or industrial spans (≥ 15m).
- Hybrid trusses combine steel joints with timber chords for cost efficiency.
- Include 5–10% extra material for connection plates and overlaps.