Give every penetration an ID and track it in one register with its location, size, service, source sheets, structural review, firestop system, and fabrication status. Freeze the register before shop drawings, and treat every later change as a tracked revision that the engineer and fabricator must accept.
Why penetrations need their own register
WoodWorks guidance on holes and penetrations in mass timber floor and roof panels says it is beneficial to model as many penetrations as possible so the manufacturer cuts them, and that the engineer should evaluate each opening for its loads and panel stresses. Penetrations through rated floors must also be protected under IBC Section 714, for example with a firestop system tested to ASTM E814 or UL 1479, and sealed to limit acoustic flanking.
The WoodWorks BC Mass Timber Construction Success Checklist (April 2025) asks whether exact penetration sizes and locations are shown on the MEP drawings, whether every penetration is coordinated with architectural and structural, and whether the supplier has defined a maximum size for field-cut penetrations. A Swinerton Mass Timber presentation for WoodWorks says all factory penetrations must be finalized during shop drawings. With hundreds of openings, those questions cannot be answered from memory. Sources verified October 22, 2026. Openings must survive the handoff described in from design model to CNC fabrication.
Fields for a penetration register
| Field | What to record | Why it matters |
|---|---|---|
| ID | One unique number per penetration, kept for the life of the project. | Lets every discipline and the fabricator refer to the same opening. |
| Location | Level, grid, panel number, and dimensions from fixed grid lines. | Panel numbers change less often than room names. |
| Size and shape | Opening size, including any sleeve or clearance allowance. | The service size is not the same as the opening size. |
| Service | What passes through: pipe, duct, conduit, sprinkler main, or a group of services. | Shows who owns the opening and who can change it. |
| Source sheets | The MEP sheet and revision that requires it, and the structural sheet that shows it. | Proves the opening appears in both disciplines. |
| Structural review | Accepted, needs reinforcement, or rejected, with the engineer’s note. | WoodWorks says each opening is evaluated for loads and stresses. |
| Fire and acoustics | Rated or not, the firestop system or tested detail, and the acoustic seal. | Rated penetrations need a tested system, and seals limit flanking. |
| Fabrication status | In the fabricator’s model, on shop drawings, approved, or field cut. | Shows which openings will arrive pre-cut. |
| Change history | Date, reason, and who approved each move or resize. | Late changes are the main source of field cuts. |
Run the register through review
- Seed it from the MEP drawings. List every penetration the MEP sets show through timber floors, roofs, and walls.
- Match it to the structural layout. Mark each opening that appears on the structural panel layout, and flag every one that does not.
- Get structural acceptance. Send openings near panel edges, beams, and supports to the engineer first.
- Add fire and acoustic details. Assign a firestop system or detail to each rated penetration.
- Freeze before shop drawings. Agree a date after which changes need a formal request.
- Reconcile shop drawings. Compare the fabricator’s shop drawings with the register, one ID at a time.
- Control late changes. Record each change, confirm the engineer and supplier accept it, and check it against the field-cut limit.
Mistakes that cause field cuts
- Counting a penetration as coordinated because it is on the MEP plan, without checking the structural layout.
- Recording the pipe size instead of the opening size.
- Moving an opening on the MEP plan after the freeze without telling the fabricator.
- Leaving rated penetrations without a firestop system until construction.
- Closing a register item before the revised sheets are issued.
Where Groundbook fits
Groundbook does not build or keep the register. It can help fill and check it. Upload the MEP, structural, and architectural sets with the specifications and run a cross-discipline review. Groundbook flags potential disagreements, such as a penetration on an MEP plan with no matching opening on the structural panel layout, with links to each source sheet. Reviewers can comment on and assign each issue, export the issues, or send them to Fieldwire as tasks pinned on the plan. A recheck of the revised set shows which issues are Fixed, Still Open, or New. Groundbook does not check structural capacity, firestop listings, or the fabricator’s model.