What to Expect from the Structural Process

Retrofit projects can have many challenges that ground up projects do not. Structurally, they’re often more involved than new construction because we’re not starting with known member sizes, connections, or a clearly defined lateral system. The first step is confirming what actually exists in the field, then designing changes that maintain gravity and seismic performance within real-world constraints.

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1) Confirm the Existing Structural System
Before we can reliably “design the change,” we need to understand the as-built conditions:

• Structural framing layout, member sizes, and spans
• Connection types and load-transfer details
• Materials and condition (corrosion, cracking, deterioration)
• Lateral system and diaphragm behavior. This typically combines record drawing review (if available) with field verification.

2) Translate Architectural Moves into Structural Impacts
Most architectural changes tend to fall into a few common structural categories:

New openings (roof, floor, wall):
Openings interrupt load paths. Structurally, we replace what’s removed and re-establish a complete path to supports.

• Roof openings may require deck-edge support and reframing.
• Wall openings often need new lintels/headers; in shear walls or bearing masonry they can also affect lateral capacity.
• Floor openings for stairs/elevators may require new beams, reinforced connections, and diaphragm checks around the opening.

Additions and new equipment:
Added area or rooftop units increase demand on beams, columns, and foundations, often beyond what the original design anticipated. Strengthening is often driven by constructability and serviceability considerations, such as deflection and vibration control, not just overall member strength.

Occupancy changes / scope triggers:
A change in use can trigger IBC/IEBC requirements, including seismic evaluation or upgrades. Identifying these triggers early helps the team develop targeted strengthening measures that meet code intent without expanding scope unnecessarily.

3) Manage Uncertainty (the Retrofit Wild Card)
Retrofits come with unknowns, missing documentation, concealed framing, undocumented prior modifications, and field tolerances that don’t match assumptions. A practical first step, selective exploratory openings, on-site measuring, and targeted analysis, helps avoid surprises during construction.

4) Why Early Coordination Matters
When structural input happens early, architects can often adjust opening locations, equipment placement, or the configuration of an addition to avoid major strengthening. The result is typically fewer RFIs, less invasive work, and a smoother path through permitting and construction.

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Retrofit projects are rarely straightforward, but with early coordination and a clear understanding of existing conditions, the structural process becomes far more manageable. When architects and structural engineers work together early, teams can reduce surprises, avoid unnecessary scope expansion, and move forward with greater confidence.