A checkable workflow
Give every measured plane or compatible group a unique name. Record its source dimensions, calculate plan area, state pitch and inspect the sloping subtotal. Add the sections and check the boundary against the original plan.
Keep additions with different pitches separate. If two sections overlap in plan, resolve the geometry before entering them; the workbench cannot detect double counting.
Unsupported information stays unsupported
Do not estimate hidden hip, valley or dormer surfaces from a broad footprint when their plan geometry is unknown. Use drawings, measured takeoff information or a competent professional.
These calculations describe geometry only. They do not size rafters or trusses, assess loads, approve a design, interpret building codes, specify cuts or fasteners, or guarantee material quantities.
Roof work can cause serious injury. Do not climb onto a roof merely to collect inputs. Prefer drawings, ground-level measurements, accessible interior information or dimensions supplied by a competent professional.
Detailed field guide
Start with a reliable plan and mark non-overlapping simple projections. Use names such as Main gable, Rear mono-pitch, Porch and Extension so every row can be traced to the drawing.
Example: 100 m² at 6/12 contributes 111.803 m²; 18 m² at 4/12 contributes 18.974 m²; 12 m² at 3/12 contributes 12.369 m². The reconciled plan total is 130 m² and sloping total 143.146 m².
Reconcile section boundaries against the overall plan. A gap indicates missing geometry; an overlap can double count. The workbench cannot inspect the plan and therefore cannot identify either condition.
Hips, valleys and dormer returns remain unsupported unless their plane projections are independently established. Sectioning is an auditable record method, not an automatic takeoff.
Checks before using the result
- Preserve the original measurement, unit, endpoints and drawing revision.
- Keep different pitches and unsupported intersections separate.
- Compare one representative result with an independent calculation.
- Do not access a roof merely to obtain calculator inputs.
Start with traceable boundaries
Work from a reliable plan and draw non-overlapping simple projections. Give each section a name that appears on both the plan and workbench. A row called “Section 3” is hard to audit; “Rear mono-pitch—east” provides a usable link back to evidence.
Choose the input method per section
Use direct area when a checked plan area already exists. Use length×width only for a genuinely rectangular projection with supported dimensions. Switching methods recalculates the row from the visible active inputs; hidden values are retained only for convenience and are never added as a second area.
Reconcile before applying pitch
First add the horizontal plan areas and compare them with the drawing or independent takeoff. A shortfall suggests a missing section; an excess suggests overlap or duplication. Only after that check should each section’s pitch factor be applied and the sloping subtotals summed.
Use duplication carefully
Duplicating a section intentionally creates another counted row, useful for matching repeated planes. Rename it and confirm that the source truly contains both copies. The duplicate-name warning is an audit prompt; software cannot decide whether two equal areas represent repetition or accidental double entry.
Create a non-overlapping plan before entering rows
Begin with a reliable plan and trace the horizontal projection of every supported roof plane. Divide only along boundaries that can be identified from the drawing or measurement evidence. Give each section a unique name that appears both on the plan and in the workbench, such as “rear mono-pitch—east.” Generic labels make it difficult to determine whether a row is missing, duplicated or attached to the wrong pitch.
Check that the sections cover the intended plan without gaps or overlap. Add their horizontal areas and compare the total with an independent footprint or takeoff where available. Perform this reconciliation before applying pitch factors. A discrepancy at the plan stage is easier to diagnose; after slope multipliers are introduced, the same gap or overlap becomes obscured by different subtotals.
Select the input method independently for each plane
Use direct area when a checked plan-projection area already exists. Use length × width only when the projection is genuinely rectangular and the two dimensions share the intended boundary. A triangular, tapered or irregular projection should not be forced into a rectangle. Determine it through an appropriate measured method outside the calculator or mark it unsupported. RoofFigured does not infer missing outlines from the building’s overall appearance.
Each row should carry its own pitch because neighbouring additions and porches may differ from the main roof. Do not average pitch values across sections. If two planes are truly identical, duplication can save entry time, but rename the copy and verify that the physical roof contains both instances. A duplicate-name warning is an audit prompt, not proof that the geometry is wrong.
Build an auditable total rather than a single number
Review each row’s name, source area, pitch, factor, sloping subtotal and validity state. Invalid rows are excluded from the aggregate and should be corrected or documented, not silently ignored. Compare the sum of plan areas with the reconciled source plan, then add the sloping areas. Large changes between versions should be traceable to a specific measurement or assumption rather than hidden inside a replaced grand total.
Export the record with a job label, timestamp and calculation version, and retain the drawing revision it relates to. Geometry is only the starting point for product takeoff: coverage, laps, cuts, waste and packaging remain separate assumptions. Where planes cannot be safely and reliably measured, obtain a competent survey or professional takeoff instead of creating enough calculator sections to make the schedule look complete.
Worked three-section reconciliation
A plan might contain a 72 m² main gable projection at 6/12, a 20 m² rear mono-pitch projection at 3/12 and a 12 m² porch projection at 4/12. The plan-area check totals 104 m² before pitch is applied. Their ideal sloping subtotals are approximately 80.498 m², 20.616 m² and 12.649 m², giving about 113.763 m². The three rows preserve the effect of each pitch; one factor applied to 104 m² would not.
Compare the 104 m² plan total with the same boundary on the drawing. If the drawing reports 110 m², investigate the 6 m² difference: a missing projection, excluded opening, overlap or mismatched wall/eaves boundary may explain it. Do not distribute the difference proportionally just to make totals agree. Record any unsupported section and obtain reliable dimensions. After reconciliation, export the schedule with the drawing revision and calculation version so the next reviewer sees both the included geometry and the remaining uncertainty.
Final verification before use
Use a row-by-row sign-off: unique plane name, source boundary, input method, plan area, pitch, factor, subtotal and status. Then sign off the plan-area reconciliation and the list of exclusions. This process prevents software convenience from replacing measurement evidence. The aggregate should be described as complete only when every intended plane is either represented by supported geometry or explicitly accounted for elsewhere.
Colouring or numbering the source plan to match the workbench rows is a practical review aid. Mark shared edges and confirm that no region carries two identifiers. When a plane is divided only for convenience but retains one pitch, the subtotals should reconcile with a single combined projection. When they do not, inspect overlap, gaps and mixed boundaries before assuming the software or factor is wrong.
Keep unsupported geometry outside the valid total with a visible note. A partial schedule can still support learning or preliminary checking if its limits are unmistakable. It becomes misleading when an omitted intersection or dormer is hidden by a generic contingency. Coverage and waste should be applied only after the geometric scope is agreed, using assumptions appropriate to the actual product and project.