Estimate preliminary steel roof frame quantities including rafters, ridge members, purlins, columns, bracing, plates, waste and material cost.
| Component | Quantity | Total Length / Area | Allowance | Estimated Weight |
|---|
The calculator first establishes the roof plan dimensions and roof pitch. For a gable roof, the horizontal half-span is converted into the sloping rafter length. For a single-slope roof, the complete roof width is used as the horizontal rafter projection.
The resulting rafter length is multiplied by the number of roof frames and the selected section weight to estimate rafter steel.
Roof frames are distributed along the building length. The calculator rounds the number of frame spaces upward so the actual frame spacing does not exceed the entered maximum.
Purlins are estimated along the roof slope. The same spacing principle is used to determine a practical preliminary quantity.
For a gable roof, one ridge member is estimated along the building length. For a single-slope roof, no ridge member is included.
Two longitudinal eave members are included for a gable roof. A single eave member is included for a single-slope roof.
Roof sheet area is based on the actual sloping roof surface rather than only the horizontal plan area. The entered sheet allowance accounts for overlaps and cutting.
The roof sheet weight is then estimated from the entered mass per square metre or square foot.
Columns are estimated from the entered quantity, eave height and column section weight. Bracing is estimated using the number of bracing sets and the average length entered for each set.
Connection and base plate steel is represented by the entered plate allowance per frame.
Individual component allowances are applied to the corresponding material group. An overall waste allowance is then added to the combined steel estimate.
The cost is a preliminary material-only estimate and does not automatically include fabrication labor, welding consumables, fasteners, coating, transportation, erection or foundations.
What does the Steel Roof Frame Material Estimator calculate?
It estimates rafters, purlins, ridge members, eave members, columns, bracing, plates, roof sheets, waste, total steel weight and preliminary material cost.
Does the calculator account for roof pitch?
Yes. Roof pitch is used to determine the sloping rafter length and actual roof surface area.
Can I select a gable or single-slope roof?
Yes. The calculator supports both preliminary roof configurations.
How are roof frames spaced?
The number of frame spaces is rounded upward from the maximum spacing entered, then the actual spacing is calculated.
How are purlins estimated?
Purlin quantity is based on the sloping rafter length and the entered maximum purlin spacing.
Does the calculator select the correct steel section?
No. You enter the section weight. The appropriate section must be selected through structural design.
Does the estimate include roof sheets?
Yes. Roof sheet surface area and estimated sheet weight are included when a sheet weight is entered.
Is this an exact bill of materials?
No. It is a preliminary takeoff intended for early estimating. Final quantities should be taken from approved drawings.