Roof trusses are pre-fabricated structural units that replace individual rafters. Calculate quantities based on spacing: Truss Count = ceil(Building Length ÷ (Truss Spacing ÷ 12)) + 1 Truss Span Distance = Building Width Linear Feet Per Truss ≈ Span × 3 (includes rafters, tie beam, and web members) Trusses are spaced along the building length (typically 16", 24", or 32" on center). Each truss spans the building width. Example: 40 ft wide × 60 ft long building, 24" spacing - Spacing in feet = 24 ÷ 12 = 2 ft - Truss count = ceil(60 ÷ 2) + 1 = 31 trusses - Each truss spans 40 feet - Lumber per truss ≈ 40 × 3 = 120 linear feet This is a preliminary estimate. Actual truss design requires engineering and may vary by load, pitch, and building code.