File Currency: What Gets Handed Over at Each Step
Lesson 6 of 18 · 6 min read
Money is the currency of a project's budget. Files are the currency of its information. Each team receives files, adds work, and passes new files on. When a format is wrong or a file is stale, work stops or goes wrong.
The common formats
| Format | What it is | Opened with (examples) | Watch out for |
|---|---|---|---|
| Fixed print of a drawing | Any PDF reader, Bluebeam Revu | Scale can change when printed or exported | |
| .dwg | 2D (or 3D) CAD drawing | AutoCAD, BricsCAD, ZWCAD | Missing xrefs, fonts and layers |
| .skp | SketchUp model | SketchUp | Geometry only, no reliable quantities |
| .rvt | Revit model | Revit | Needs the same or newer Revit version |
| .pln | Archicad project | Archicad | Same issue with versions |
| .ifc | Open BIM exchange | Most BIM tools and free viewers | Export settings decide what data survives |
| .e2k / .std | Structural analysis model | ETABS / STAAD.Pro | Analysis only; not a drawing |
| .xlsx | Spreadsheet: BOQ, BBS, rate analysis | Excel, Google Sheets | Broken formulas, hidden rows |
| .mpp | Schedule | Microsoft Project | Needs the desktop app to edit |
| .xer | Schedule | Primavera P6 | Calendar and code settings travel with it |
| COBie | Asset data for handover | Spreadsheet or FM software | Only as good as what was filled in |
What gets lost at each hand-off
- DWG to PDF: layers and exact geometry are flattened. Scale can drift if the PDF is printed "fit to page".
- Model to drawings: if drawings are exported once and the model keeps changing, the two drift apart.
- Native BIM to IFC: some parameters or custom properties may not export. Always open the IFC in a viewer and check.
- Drawings to Excel: this is the big manual step. A QS reads the drawings and types quantities. It is slow, and errors here flow straight into the budget.
- Excel to schedule: BOQ items rarely match schedule activities one to one. Someone has to map them.
- Site to office: DPRs and measurements often travel as photos and WhatsApp messages, then get re-typed.
A worked example: a stale PDF
A contractor receives the BOQ in .xlsx and the drawings in PDF in March. In April the architect issues revision R3 of the ground-floor plan, moving a toilet. The contractor's QS keeps measuring from the March PDF.
The moved toilet adds 6 sq m of wall tiling and 4 m of extra pipe. At ₹1,100 per sq m for tiling and ₹450 per metre for CPVC pipe with fittings (illustrative), that is ₹6,600 + ₹1,800 = ₹8,400 missing from one bill. Nobody notices until the final account.
The fix is simple: a drawing register that lists the latest revision of every sheet, checked before each measurement.
Good habits
- Ask for both .dwg and PDF of GFC drawings. PDF to read, DWG to measure.
- Ask for IFC if you need a model and do not use the designer's software.
- Name files with sheet number and revision, not "final" or "latest".
- Keep one shared folder as the single source. Forwarded copies on WhatsApp are not the record.
What comes next
Module 3 looks inside engineering: how structural analysis becomes reinforcement drawings and a BBS, and how services are coordinated.
Key takeaways
- Files are the currency of project information; each hand-off is a file.
- PDF is for reading; DWG is for measuring; IFC is for exchanging models.
- Each conversion loses something: layers, data, scale or freshness.
- The drawings-to-Excel step is the biggest manual hand-off and the biggest source of budget errors.
- A drawing register with revisions prevents measuring from stale files.
Verify on site
- Check the revision on every sheet before you measure from it.
- Ask the designer for .dwg as well as PDF for the GFC set.
- Rename files with sheet number and revision.
Check your understanding
3 questions. Answering them marks this lesson complete — results stay on your device.
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