Input Details
Example Data Table
Sample inputs for a small heritage wing survey.
| Space | Shape | Dimensions | Area (m²) | Include |
|---|---|---|---|---|
| Main Hall | Rectangle | 12 × 8 | 96.00 | Yes |
| Gallery Wing | Rectangle | 10 × 6 | 60.00 | Yes |
| Apse | Circle | r = 3 | 28.27 | Yes |
| Courtyard | Custom | Measured | 24.00 | No |
Formula Used
- Rectangle: Area = Length × Width
- Triangle: Area = ½ × Base × Height
- Circle: Area = π × Radius²
- Custom: Area = Entered measured area
The non-usable allowance is a practical heritage placeholder for thick masonry walls, restricted conservation areas, and heavy circulation zones.
How to Use This Calculator
- Select the measurement unit you recorded on site.
- Enter the number of floors included in the survey scope.
- Add spaces/rooms and choose a shape for each entry.
- Tick “Include” for enclosed floor areas you want counted.
- Enter courtyard and void deductions if applicable.
- Set a non-usable allowance to reflect heritage constraints.
- Press Calculate area to see results above the form.
- Use CSV/PDF buttons to export for reports and submissions.
Survey inputs aligned with heritage workflows
Field surveys often mix measured rooms and traced irregular spaces. This calculator accepts meters or feet, then converts results automatically. Recording floors matters because gross area scales linearly. For example, 3 floors of 150 m² per floor produces 450 m² gross before deductions. Notes preserve scope decisions, such as excluding unsafe wings, for later review.
Room table for mixed geometry
Spaces can be rectangles for halls, circles for apses, triangles for wedge bays, or custom areas from CAD traces. Each row can be included or excluded, so open courts and uncovered verandas stay out of enclosed floor totals. The breakdown table keeps the selected formula beside every area, supporting transparent checking. Add separate rows for wings to mirror drawing packages and phases.
Gross and net outputs for reports
Gross per floor is the sum of included space areas. Gross all floors multiplies by the floor count. Net usable is estimated by subtracting a courtyard deduction, voids per floor, and a percentage allowance. The page also shows an efficiency ratio to compare assumptions across phases. Keep prior exports to track changes between concept and as-built.
Deductions that reflect conservation constraints
Heritage buildings often include thick walls, protected fabric buffers, and limited-use zones. The non-usable allowance models these constraints as a percentage of gross area, commonly set between 8% and 20% depending on construction and restrictions. Voids per floor represent stair cores, double-height volumes, and shafts. Courtyard area is deducted once to represent open-to-sky courts that do not add enclosed floor area.
Export controls for documentation and audits
CSV export captures all inputs in a shareable format for spreadsheets and estimating tools. PDF export summarizes key metrics and includes the room list for appendices in condition reports. Printing uses a clean layout so reviewers can sign off on assumptions and keep a dated calculation record. Store exports with drawing revisions and survey dates for traceability. PDF export also records unit settings, floors, and allowance values clearly.
FAQs
1) What does “net usable” represent in this tool?
Net usable is an estimate after deducting courtyards, voids, and a non-usable allowance. It supports planning comparisons, but final certified areas should follow your authority’s measurement standard and drawings.
2) How should I set the non-usable allowance percentage?
Start with a conservative range such as 8–20%, then adjust based on wall thickness, protected zones, and circulation. Keep the chosen value consistent across revisions so stakeholders can compare scenarios reliably.
3) When should I exclude a space using the Include checkbox?
Exclude open-to-sky courts, exterior balconies, and areas outside the survey scope. Also exclude unsafe or inaccessible wings until they are measured. Document exclusions in the notes field for transparency.
4) Can I use the calculator for irregular rooms?
Yes. Measure the irregular boundary using tracing, CAD, or scan processing, then enter the computed value as Custom area. Keep the underlying sketch or trace so reviewers can verify the source measurement.
5) Why is courtyard area deducted only once?
Courtyards are usually open spaces that do not create enclosed floor area across stacked floors. Deducting once approximates an open-to-sky court. If your building has multiple courts on different levels, enter them separately.
6) Do the exports include my input table and assumptions?
Yes. The CSV includes every row and all settings. The PDF summarizes key metrics and lists spaces, plus unit, floors, and allowance values. Save exports with survey dates and drawing revisions.