Start with the construction type and code edition in the code analysis, then check that every exposed timber surface on the plans and reflected ceiling plans is allowed for that type, that protected surfaces have a protection detail, and that connections and penetrations keep the required rating. Ask the architect and fire consultant to resolve any surface shown exposed on one sheet and protected on another.
How construction type limits exposed timber
The 2021 IBC added Types IV-A, IV-B, and IV-C for tall mass timber. ICC’s Building Safety Journal describes IV-A as fully protected with noncombustible protection, IV-B as mostly protected, and IV-C as mostly unprotected. It adds that even in IV-C, noncombustible protection is required for concealed spaces, shaft walls, and the exterior surface of outside walls.
WoodWorks’ summary of exposed timber allowances says IV-A permits no exposed timber, IV-C permits full exposure, and IV-B permits partial exposure. For IV-B it reports that the 2021 IBC allowed 20% of ceilings, 40% of walls, or a combination, and that the 2024 IBC permits fully exposed timber ceilings. Because the limits changed between editions, confirm which edition and local amendments your jurisdiction has adopted. Sources verified October 22, 2026.
Where the documents must agree
| Item | Documents involved | What to check |
|---|---|---|
| Construction type and edition | Code analysis, cover sheet, structural notes | One construction type and one code edition are stated across the set. |
| Exposed surfaces | Floor plans, reflected ceiling plans, interior elevations, finish schedule | Every surface shown as exposed is allowed for the type and edition, and exposed areas are tracked where the type limits them. |
| Protected surfaces | Wall and floor types, details, specifications | Each protected surface has a protection layer and detail, and the finish schedule does not show it as exposed timber. |
| Concealed spaces and shafts | Sections, shaft details, ceiling details | Required noncombustible protection is shown at concealed spaces and shaft walls. |
| Member ratings | Structural drawings, fire-resistance basis, code analysis | The rating each member needs is stated, and the compliance basis (test or calculation) is referenced. |
| Connections | Connection details, fire details, specifications | Connections in rated assemblies are protected for the required time, with the basis referenced. |
| Penetrations | MEP plans, firestop details, specifications | Each penetration through a rated floor or wall has a firestop system or tested assembly detail. |
Connections and penetrations keep the rating
WoodWorks’ March 2026 paper Fire Design of Mass Timber Connections explains that in Types IV-A, IV-B, and IV-C, connections used with rated members must be protected for the time of the rating, shown either by fire testing or by engineering analysis. It notes that calculated fire resistance of exposed wood under NDS Chapter 16 is limited to 2 hours, and that a connection between rated members needs protection at least equal to the rating of the supported member. See mass timber connection coordination for the questions to settle.
For penetrations, WoodWorks’ penetration guidance says they must be sealed and protected under IBC Section 714, using tested assembly details or a firestop system tested to ASTM E814 or UL 1479. The firestop checks continue in the ASTM E814 and UL 1479 firestop guide.
Published example: a rating that differs between two documents
This finding comes from a hotel project, not a mass timber one, but it shows the same kind of disagreement. In the published door-rating finding, sleeping-unit entry doors opening into an interior lobby were marked unrated in the door schedule, while the surrounding separation called for protected openings.
In an exposed mass timber building, the same pattern shows up when a finish schedule calls a surface exposed timber while the wall or floor type calls for protection. Check each exposed surface against both documents, and have the architect reconcile them before fabrication and finish procurement.
Record each question so it can be closed
For each issue, record the room or area, the sheets and schedules involved, the construction type and edition, and who must decide. When exposure changes, check the reflected ceiling plans, finish schedule, wall and floor types, and connection details together. The IBC Chapter 6 guide covers construction type review in general.
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.