Coordinate every point where mass timber meets concrete or steel: the embed or anchor, the bearing elevation, the hardware supplier, and the tolerance each trade must meet. Settle these in the drawings and specifications before the concrete is placed and before the timber is detailed.
Why the interfaces need extra attention
WoodWorks notes in its Index of Mass Timber Connections (updated March 2025) that mass timber fabrication tolerances are extremely precise and might be as low as ±1/16 inch, while steel, concrete, and masonry tolerances can be larger. Most structures have some interface between timber and these materials, so the relative tolerances must be considered.
The WoodWorks BC Standard Connections paper (December 2025) says the same and adds that members and connections should be designed with field modifications in mind. A Swinerton Mass Timber presentation hosted by WoodWorks advises that other structural trades have their shop drawings and 3D model approved and locked before timber detailing starts. Sources verified October 22, 2026. Where timber floors meet a concrete core, see differential movement in tall mass timber buildings. Toppings poured over the panels are covered in concrete toppings on mass timber floors.
Interfaces to coordinate
| Interface | What to coordinate | Documents to compare |
|---|---|---|
| Foundations and podiums | Bearing elevations, base plates, anchors, and grout under column bases. | Foundation and podium plans, column base details, timber framing plans |
| Concrete cores and walls | Embeds or post-installed anchors for beams and panels, and their locations and elevations. | Concrete wall elevations and embed schedules, timber connection details |
| Steel beams and frames | Panel and beam bearing on steel, connection plates, and fastener access. | Steel framing plans and shop drawings, timber panel layout |
| Miscellaneous steel hardware | Which supplier provides hangers, drag plates, and knife plates. | Mass timber and structural steel specification sections |
| Lateral system | How the timber diaphragm connects to concrete or steel lateral elements, and drift compatibility. | Lateral drawings, collector and drag details, structural notes |
| Concrete toppings | Topping thickness, reinforcement, and how it meets cores and walls. | Floor assembly types, structural sections, specifications |
Eight interface checks
- Embed or anchor. Confirm each timber connection to concrete states whether it uses an embedded or post-installed anchor. WoodWorks notes the location, geometry, and contractor preference drive the choice.
- Embed locations. Compare embed locations on the concrete drawings with the timber connection details. A misplaced embed is very hard to fix after the pour.
- Bearing elevations. Compare top-of-concrete and top-of-steel elevations with the timber framing elevations. Check that both use the same datum.
- Tolerance requirements. Check whether tighter tolerances are required from the concrete and steel trades at timber interfaces, and that those requirements are in their scopes.
- Adjustability. Confirm the details include a way to absorb variation, such as grouted base plates, shims, or slotted holes. The Standard Connections paper notes a custom hanger may allow more placement tolerance at a concrete interface than a dovetail hanger.
- Hardware scope. Compare the mass timber and steel specification sections item by item, so each hanger and plate has one supplier.
- Shop and field work. Check that the drawings separate shop-installed and field-installed connection work. The Standard Connections paper recommends clearly delineating these scopes.
- Welding near timber. Where welding happens next to installed timber, confirm the project has a fire-safety plan for it, as the WoodWorks BC checklist asks.
Published example: floor elevations that differ between disciplines
This finding comes from a concrete project, not a mass timber one. In the published floor-elevation finding, structural and mechanical plans showed different elevations for the same floor area. At a timber-to-concrete interface, the same disagreement would set a bearing seat or embed at the wrong height. Compare elevations and datums across every set that touches the interface.
Check the existing conditions before installation
The WoodWorks BC and Seagate Mass Timber checklist asks, about three weeks before work on site, whether the existing structure is within tolerance for mass timber, such as whether embeds are out of place. Survey the concrete and steel that the timber will bear on, and compare the results with the timber shop drawings while there is still time to adjust. The mass timber tolerances guide covers this in more detail.
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.