The Architect's Guide to Structural Coordination

Coordinating with a structural engineer is a high-stakes balancing act. Misalignment leads to non-compliant wet areas, exposed structural beams, and water ingress. This guide serves as a coordination bridge, ensuring structural data is accurately integrated across your plans.

1. WHEN ARE STRUCTURAL ENGINEERS ENGAGED & FOR WHICH BUILDING CLASSES?

• Timing: Engaged early in Concept or Schematic Design to establish key structural parameters, remaining on board through to Construction documentation.

• Classes: All building classes.

2. WHAT INFORMATION DO THEY PROVIDE, AND HOW DO YOU COORDINATE IT?

A. Termination Heights

• The Driver: Slab setdowns and wet areas are an architect-driven, design-based process. You dictate these spatial requirements to the structural engineer based on your interior finishes and waterproofing strategy.

• Termination Height & External Setdowns: The termination height is critical for weatherproofing and is advised by the structural engineer. It establishes the primary baseline level from which all external step-downs are calculated to keep water out.

  • Compliance Note: AS 4654.2 details how the termination height is calculated. However, NCC 2025 introduces a strict minimum structural slab setdown requirement of 70mm between internal and external spaces. If the AS 4654.2 calculated termination height requires a drop greater than 70mm, you must adopt the greater depth to ensure both standards are met.

• Wet Areas & Balconies: You must specify the exact setdown depth required to accommodate screed, drainage falls (min 1:80 & max 1:50), finishes, and waterproofing (AS 3740).

• Action Checklist:

  • Cross-check the Structural Engineer’s termination height requirements against the external slab setdown threshold detail.

  • Show all setdowns clearly on your Architectural Concrete Setdown Plan.

  • Cross-check the structural drawings to ensure the engineer has accurately captured your specified setdown dimensions.

  • Cross-check the lowest point of your architectural setdown to ensure it still maintains the minimum structural slab thickness required by the engineer.

B. Slab Penetrations for Services

• Action: Cross-check that the Structural Engineer has accounted for all slab penetrations in the structural design calculation to avoid future slab thickening or increases to column and beam sizes.

C. Sub-Structure: Piles & Capping Beams

• Information Source: Physical locations of piles and top-of-concrete RLs for capping beams are usually provided by the Structural Engineer. However, in D&C projects, the specific pile locations and types may come from a Piling Contractor’s Shop Drawings.

• Architectural Check:

  • The Layout Match: Verify that the Piling Contractor’s shop drawings match the Structural Engineer’s capping beam layout and flag any discrepancy.

  • Coordinate site services and structural foundation: Overlay  Hydraulic site plan, Electrical site plan, Civil plans & Structural Foundation Plan onto the architectural early works plan and coordinate how the services run into the building. Trace the High Voltage (HV) conduit path and coordinate the path between structural and electrical consultants.

  • The Capping Beam: Ensure the capping beam level is coordinated with finished ground levels and site drainage requirements set by the civil engineer.

D. Slab thickness & thickenings.

• Architectural Check:

  • Cross-check the architectural concrete setdown plans to ensure they meet the minimum slab thickness nominated by the structural engineer and that all slab thickenings shown on the structural drawings are captured.

  • Review the RCPs at the level below to ensure services can clear slab thickenings while maintaining the required clear head heights. 

• Where head height compliance cannot be achieved, coordinate with consultants to either :

  • Reroute services, 

  • Reduce duct depth by reconfiguring duct sizing,

  • Introduce compliant bulkheads, or

  • Investigate structural web penetrations where feasible.

E. Vertical Skeleton: Columns & Walls

• The Fit Test: Verify that structural column profiles (SHS, UC, etc.) actually fit within your stud walls.

• Architectural Check:

  • Cross-Check Layouts: Never assume a column fits. If a 100mm SHS is placed in a 92mm stud wall, the geometry must be resolved before the drawings are issued.

  • The Domino Effect: If thickening the wall is required, verify it doesn't reduce corridor widths below NCC minimums or obstruct door clearances.

• How to Resolve a Clash:

  • Structural Alternative: Ask the Structural Engineer if the profile can be changed (e.g., switching from a square SHS to a flatter, wider Universal Column) to suit the architectural wall depth.

  • Geometry Fix: Only change the wall thickness once you have verified that the room areas, paths of travel, and door swings remain compliant.

3. COMMON COORDINATION PITFALLS

• The Setdown Domino Effect: If the external threshold setdown details are incorrect, every balcony setdown will lack the depth required for weatherproofing, resulting in non-compliant thresholds.

• The "Fit Test" Oversight: Failing to coordinate structural steel sizes with architectural wall types will result in the columns/beams protruding from finished walls. This forces an unplanned thickening of the partition on-site, which usually results in awkward, unplanned column/beam box-outs, or stealing valuable square meterage from adjacent, tightly planned rooms. 

• The Hidden Slab Thickening Clash: If slab thickenings are not coordinated into the architectural setdown plans and RCPs, services at the level below may clash with the structure, resulting in non-compliant head heights, oversized bulkheads, or late-stage service rerouting.

The Superseded File Trap: Coordinating against outdated structural or services drawings will lead to misaligned slab penetrations and incorrect floor levels; this results in costly on-site structural modifications if caught too late.