Information is usually lost at handoffs: when design changes arrive after the fabricator’s model is built, when other trades’ models are not locked, when shop drawing questions stay open, and when existing conditions were never measured. Lock inputs in order, reconcile shop drawings with the current contract set, and close every question before production.
How a panel goes from drawing to machine
Fabricators build their own detailed model from the contract documents. Western Forest describes its mass timber project management this way: coordinated 3D models support design, clash detection, shop drawings, and CNC fabrication, and detailed shop drawings define all components, including connections, tolerances, and interfaces. The shop drawings and the model then drive production.
That means the fabricator’s model is only as current as the information it was built from. A Swinerton Mass Timber schedule presentation for a WoodWorks workshop (November 2019) shows the order on real schedules: mass timber shop drawings, a fabrication-ready steel model, MEPF model sign-off, shop drawing review and approval, and finalized drawings before production and delivery. Sources verified October 22, 2026.
Five handoffs where information gets lost
| Handoff | What gets lost | Check that closes it |
|---|---|---|
| Design drawings to fabricator model | Changes issued after the fabricator started detailing, such as a moved opening or resized beam. | Compare the revision the fabricator detailed from with the current set, sheet by sheet. |
| Other trades to timber | Steel and concrete dimensions that change after timber detailing starts. | The Swinerton presentation says other structural trades must have shop drawings and 3D models approved and locked for fabrication before timber detailing starts, or risk rework. |
| MEP to timber | Penetrations added or moved after the MEP model is signed off. | Set an MEPF sign-off date tied to timber shop drawing review, and track every penetration after it. |
| Shop drawing comments to production | Questions that stay open, or answers that never reach the revised shop drawings. | The presentation warns that lingering shop drawing questions can drag on for weeks or months. Close each one in writing before release. |
| Site to factory | Existing or as-built dimensions that were never measured. | WoodWorks says critical dimensions should be obtained early, and describes a project where panels made without a full scan needed site adjustments. |
Scope gaps that the model will not show
Some information is lost because no one owns it. The WoodWorks BC Mass Timber Construction Success Checklist (April 2025) asks whether miscellaneous steel hardware, such as beam hangers and drag plates, is clearly divided between the mass timber and steel suppliers, and whether coatings are defined in the architectural and structural specifications, including whether they are shop or field applied. It also asks whether visual expectations for exposed delegated-design timber elements were discussed with the design team and owner. A fabricator model can be complete and still leave these unresolved.
Checks before production starts
- Confirm which revision of every discipline the fabricator detailed from, and list every later change.
- Compare shop drawings with the current contract drawings and specifications, including connections, hardware, and coatings.
- Check that every penetration on the current MEP drawings appears on the shop drawings.
- Confirm steel and concrete interfaces were taken from locked, approved models or shop drawings.
- Check that existing or as-built dimensions come from a survey, not from old drawings alone.
- Close every shop drawing comment and confirm the answer appears on the revised sheets.
For vertical additions and other work on existing buildings, the site-to-factory handoff matters most. See the WoodWorks guidance on surveying before fabrication.
Where Groundbook fits
Groundbook reviews PDF and DWG drawings, specifications, and references. It does not read the fabricator’s model or CNC files. Use a shop drawing review to compare the fabricator’s shop drawings with the contract drawings and specifications. Groundbook flags potential disagreements with links to the design references, and can overlay two drawings at a finding, aligned by AI, so you can see what moved between revisions. The engineer or architect of record still reviews the shop drawings for conformance with the design.