Roof Truss Load Planning
Roof truss load work starts with clear assumptions. A truss does not carry the whole roof alone. It carries the roof strip halfway to each neighboring truss. That strip is called the tributary width. This calculator converts spacing into that width, then applies roof loads to the supported area.
Why Loads Matter
Dead load comes from shingles, sheathing, purlins, insulation, and the truss itself. Ceiling load covers drywall, battens, lights, and small service items. Live load reflects workers, maintenance, and movable roof effects. Snow load may replace live load when it is larger. Wind uplift acts upward and can reduce bearing compression or demand stronger tie down hardware.
A pitch correction is also useful. A steep roof has more sloped surface than its horizontal plan. The slope factor estimates that increase from the selected pitch. Dead load may follow the sloped surface. Snow and live load are commonly treated on the horizontal projection for preliminary planning.
Using the Results
The service load shows the expected unfactored downward load per truss. The factored design load applies common strength style multipliers and the selected safety factor. The reaction value divides the downward load between two equal bearings. Real trusses may have different reactions when there are cantilevers, hips, valleys, concentrated tanks, solar panels, or unequal support points.
The uplift check compares wind suction with stabilizing gravity load. A positive net uplift means the truss may try to lift from its bearing. Connectors, hurricane ties, straps, bolts, and wall anchorage should then be reviewed.
Good Practice
Use this tool for early estimating, quoting, and discussion. It is not a substitute for engineered truss drawings. Local codes, lumber grades, metal plate design, deflection limits, bracing, load combinations, and snow drift rules can change the final answer. Always send accurate spans, spacing, pitch, overhangs, and load assumptions to a qualified designer. Keep a copy of the CSV or PDF with the project notes. That record helps compare options and explain why a spacing or member size was selected. Before ordering materials, test several spacing values. Small changes can affect reactions, uplift, connector demand, and roof area. Save each scenario. Always compare totals with the truss supplier before confirming the final layout.