Steel framing
Routing Building Services Through CFS Floor Joists
Coordinate service routes with actual CFS joist openings, bridging, supports, insulation, and access before floor fabrication.
The condition to resolve
A duct centerline can pass through a joist opening in the model while its insulation, flange, or support cannot. Plumbing slope and sprinkler branches introduce additional constraints. Manufacturer openings vary by product and depth, so the services team needs the identified joist layout rather than a generic hole symbol.
Coordinate before releasing the work
Model the outside dimensions of services and their installation access. Compare them with factory opening locations, bridging, and end connections. Identify routes that depend on consecutive aligned openings or change elevation. Obtain reviewed alternatives for conflicts before fabrication; field enlargement or relocation of a hole requires a specific structural disposition.
How it fits the building system
A cold-formed steel floor is an assembly of joists, supports, restraint, deck or sheathing, finishes, and connections. Review the entire assembly rather than ordering joists from a span alone. Manufacturer data describes specific products and conditions; the project designer must reconcile those conditions with the building's loads, openings, and supporting construction. Product substitutions can change interfaces even when the nominal member depth remains the same.
Prepare a coordinated floor section showing the structure, service zone, ceiling, and finished floor elevation. Locate bearing lines and special openings in plan, then track the details that cannot be seen after enclosure. Before releasing an area for subsequent work, check that temporary construction activities and stored materials follow the approved construction plan. A finished-floor review and an installation-stage review answer different questions.
References: TradeReady steel joists: system data and application limits · TradeReady floor joist blocking · Current technical notes for CFS walls, floors, connections, and inspection
Practical location-based review
Assign an owner, location, and response document to each check. Include affected trades before fabrication or concealment; final dimensions and connections belong in the approved project documents.
- Use full insulated service dimensions instead of centerlines alone.
- Check consecutive joist openings against sloped and branching routes.
- Keep bridging and joist-end connections in the conflict review.
Documents and decisions that must agree
Keep this comparison beside the current drawing. Record discrepancies as specific questions and preserve the response in that area's records.
| Item | Evidence needed | Decision to confirm |
|---|---|---|
| Service envelope | Insulated dimensions and supports | Clear route |
| Joist holes | Actual product opening layout | Compatible factory geometry |
| Conflict | Location-specific coordination request | Reviewed alternate route |
Verification and handoff to the next trade
During rough-in, verify the installed route against the accepted service overlay and record any changed joist or support locations. Check that the chosen route has not displaced required restraint or introduced attachments absent from the reviewed package. The service installer should report interference before concealment, with the joist mark and full outside service dimensions. Preserve accepted routing changes for maintenance access and future alterations rather than leaving the actual route known only to the installing crew.
Give the next trade the current detail, the restrictions it must preserve, and open observations. Verify the installed work before concealment and retain an identifiable location in the final record.
Common questions
Do large factory openings permit any service size?
No. Use the product's actual opening geometry and the service envelope, including insulation and installation clearance. Coordinate structural and assembly requirements for the proposed route.
Can bridging be removed to route a duct?
Do not remove a designed restraint without review. Ask the floor designer and service team to coordinate an approved route or revised restraint detail.
Sources & further reading
Use the current documentation for the exact product and project. Source links do not imply a partnership or endorsement.
- TradeReady steel joists: system data and application limits ClarkDietrich
- TradeReady floor joist blocking ClarkDietrich
- Current technical notes for CFS walls, floors, connections, and inspection Cold-Formed Steel Engineers Institute
Prepared with AI assistance. Linked references require current project-specific review. How these guides are prepared.
Prepare a supply inquiry
- Record the project drawing or detail and the specified product, profile, or system.
- List the complete configuration, physical units, quantities, and cuts per piece.
- Request current manufacturer documents; confirm compatibility, price, and availability before ordering.
- Obtain the responsible professional's review for loads, code requirements, or installation.