Before mass timber drawings are released for fabrication, confirm that grids, levels, panel layouts, openings, connections, and protection requirements agree across the architectural, structural, and MEP sets. Every penetration should have a final size and location that the structural engineer has reviewed, because changes are much harder once the panels are cut.
Why mass timber needs coordination earlier
On a concrete or steel project, many openings and attachment details can still be settled during construction. Mass timber moves those decisions forward. WoodWorks advises that it is beneficial to model as many of the penetrations and holes as possible so the manufacturer cuts them, which gives better accuracy and a cleaner finish than cutting in the field. The same guidance notes that no U.S. design guide prescribes acceptable openings in CLT floors and roofs, so the engineer evaluates each one for its loads and panel stresses.
The Mass Timber Construction Success Checklist from WoodWorks BC and Seagate Mass Timber (April 2025) makes the same point from the contractor’s side: penetrations that are not fully coordinated before tender can delay fabrication, and site penetrations should be avoided. Sources verified October 22, 2026.
What each discipline should verify
| Discipline | What to verify | Where it shows up |
|---|---|---|
| Architect | Construction type, exposed and protected timber surfaces, finishes, and openings in walls, floors, and roofs. | Code analysis, plans, reflected ceiling plans, wall and floor types, details |
| Structural engineer | Panel layout and span direction, beam and column sizes, connections, and every opening the panels must carry around. | Framing plans, panel layout, connection details, general notes |
| MEP engineers | Final size and location of every penetration, and the services that run exposed below the timber. | Plumbing, mechanical, electrical, and fire protection plans and risers |
| Fire protection and code | Penetration firestopping, concealed spaces, and the protection the construction type requires. | Code analysis, life safety plans, firestop details, specifications |
| Contractor and fabricator | Tolerances at concrete and steel interfaces, the limit on field-cut openings, hardware scope, and installation sequence. | Specifications, interface details, shop drawings, fabrication model |
Twelve checks before the fabrication release
- Construction type. Confirm the code analysis, structural notes, and details name the same Type IV subdivision, and that the protection shown matches it. The 2021 IBC added Types IV-A, IV-B, and IV-C, which differ in how much of the timber must be protected.
- Grids and levels. Compare grid spacing, grid names, and level elevations across the architectural, structural, and MEP sets. A small grid offset becomes a misplaced opening in every panel along that line.
- Panel layout. Check that panel joints, span directions, and edges agree between the structural panel layout and the architectural plans and reflected ceiling plans.
- Penetration locations. Trace every pipe, duct, conduit, and sprinkler penetration from the MEP plans to the structural panel layout. Each one should appear in both with the same size and position.
- Opening review. Confirm the structural engineer has reviewed each opening, including openings near panel edges, beams, and supports. Large openings may need reinforcement or added framing.
- Field-cut limit. Check whether the specifications or supplier define the largest opening that may be cut on site, and that the trades know the limit.
- Firestopping. Check that each penetration through a rated floor or wall has a referenced firestop system or tested assembly detail. Mass timber penetrations are protected under IBC Section 714.
- Concealed spaces and shafts. Confirm the protection required at concealed spaces and shaft walls is shown. ICC notes that even Type IV-C requires noncombustible protection there.
- Connections. Compare connection types and hardware between the structural details, the specifications, and the architectural intent for exposed connections.
- Concrete and steel interfaces. Check embeds, anchor locations, and bearing elevations where timber meets cores, podiums, and steel. Ask whether tighter tolerances are required from those trades and whether that requirement is in their scope.
- Exposed surfaces. Compare the timber surfaces shown as exposed on architectural plans with the finish, coating, and appearance requirements in the specifications.
- Hardware scope. Confirm the specifications divide items such as beam hangers and drag plates clearly between the mass timber supplier and the steel supplier.
Published example: an opening shown in only one discipline
This finding comes from a concrete project, not a mass timber one, but it is the failure that matters most before fabrication. In the published missing-opening finding, a sump on the mechanical and plumbing plans had no matching opening in the structural slab and footing information.
On a concrete project, a gap like this can sometimes be fixed before the pour. On a mass timber project, the same gap reaches the factory, and the opening is either missing from a finished panel or cut in the field. Checking every penetration across both disciplines before release is the main reason to run this checklist.
Record each question so it can be closed
For each issue, record the grid or panel location, both source sheets and their revisions, what disagrees, who must answer, and whether the answer changes the fabrication package. After a response, check the revised sheets and every affected panel before closing the item.
Use the editable document review log to keep the evidence together. The WoodWorks design and cost optimization checklists cover the earlier design decisions, such as grids and spans, that make this review easier.
Where Groundbook fits
Upload the architectural, structural, and MEP drawings with the relevant specification sections, and run a cross-discipline review. Groundbook flags potential disagreements, such as an opening shown on an MEP plan but missing from the structural panel layout, with links to each source sheet. Your team decides what each finding means for the fabrication package. Groundbook does not check structural capacity, fire ratings, or the fabricator’s model.