11.3 Evaluating an Existing Building Against a Program
Key Takeaways
- Existing structural bay spacing and load capacity often govern whether a program can be accommodated at all, independent of area.
- As-built drawings are frequently inaccurate, so a measured field survey must verify conditions before design proceeds.
- Existing-building codes classify work as repair, alteration levels 1 through 3, change of occupancy, or addition, and the classification determines the required upgrades.
- A change of occupancy drives occupant load, exit capacity, plumbing fixture counts, and often sprinkler and alarm requirements, making it the largest cost driver in adaptive reuse.
- Altering a primary function area triggers an obligation to make the serving path of travel accessible, subject to the disproportionate-cost limitation.
Objective 4.1 asks you to evaluate the relevant qualitative and quantitative attributes of a new or existing building as they relate to a program. The word that carries the weight is existing: a large share of architectural work is renovation, addition, adaptive reuse, and change of occupancy, and the evaluation methods differ from those used on a greenfield site.
What an Existing-Building Evaluation Measures
Quantitative Attributes
| Attribute | How it is established | Why the program depends on it |
|---|---|---|
| Gross and net area by floor | Measured survey or verified as-builts | Determines whether the program fits at a realistic efficiency ratio |
| Floor-to-floor and floor-to-deck height | Field measurement | Governs ceiling height, duct depth, and whether new MEP can be routed |
| Structural bay spacing and capacity | Original drawings plus structural assessment | Governs layout flexibility and whether new loads — assembly occupancy, file storage, green roof, rooftop equipment — can be carried |
| Existing MEP capacity | Equipment nameplate data, panel schedules, service size | Determines whether a change of use can be served without new service |
| Envelope thermal performance | Assembly investigation, infrared survey, blower-door testing | Governs energy compliance and comfort |
| Egress capacity | Measured stair widths, exit counts, travel distances | Caps the occupant load the building can legally hold |
| Vertical transportation | Elevator count, capacity, speed | Caps population and governs accessibility |
Qualitative Attributes
- Architectural significance and whether the building is listed, contributing to a district, or eligible for listing.
- Condition of structure, envelope, and systems, expressed as remaining service life rather than as a simple pass or fail.
- Spatial character — daylight, volume, column rhythm, materials — which is usually the reason the reuse is attractive in the first place.
- Hazardous materials, particularly asbestos, lead paint, and PCBs in buildings of certain eras. A hazardous-materials survey precedes any demolition planning.
- Adaptability: how much of the program can be accommodated without altering the structure.
The Evaluation Sequence
- Document review. Original drawings, prior permits, prior renovation records, certificate of occupancy, and any existing conditions reports.
- Measured survey. Verify, never assume. As-built drawings are frequently wrong, and the error is discovered at the worst moment.
- Discipline assessments. Structural, MEP, envelope, and where relevant a hazardous-materials survey and an accessibility audit.
- Code evaluation under the jurisdiction's existing-building provisions.
- Program fit test. Block the program into the measured building and report the surplus or deficit.
- Feasibility recommendation comparing reuse against new construction.
Code Path for Existing Buildings
Most jurisdictions adopt an existing-building code (commonly the International Existing Building Code, IEBC) or the existing-building chapter of the building code. The evaluation must establish which work classification applies, because that determines how much of the building must be upgraded:
| Work type | Trigger | Typical requirement |
|---|---|---|
| Repair | Restoring damaged work | Repair to pre-existing condition |
| Alteration Level 1 | Replacement of materials with equivalents | Minimal upgrade |
| Alteration Level 2 | Reconfiguration of space, new systems | Upgrades within the work area |
| Alteration Level 3 | Work area exceeds 50% of building area | Building-wide upgrades to selected systems |
| Change of occupancy | New occupancy classification | Compliance with the requirements of the new occupancy |
| Addition | New construction added | Addition meets new-construction requirements; existing building must not be made less compliant |
Change of occupancy is the trigger that moves budgets the most. Converting a Group B office floor to a Group A-2 assembly use raises occupant load dramatically, which in turn drives exit capacity, plumbing fixture counts, and sometimes sprinkler and alarm requirements. Converting an office building to Group R residential brings dwelling-unit separations, sound transmission requirements, and different egress rules.
Accessibility in Existing Buildings
Alterations must comply with accessibility requirements to the maximum extent technically feasible, and altering a primary function area triggers an obligation to make the path of travel to that area — including restrooms, drinking fountains, and telephones serving it — accessible, subject to a disproportionate-cost limitation in the ADA regulations. Existing buildings that are not being altered still owe readily achievable barrier removal in places of public accommodation.
Exam Tip: When a programming item involves an existing building, look first for a change of occupancy and second for a structural capacity limit. Those two facts drive more feasibility answers than any aesthetic or condition issue, because they determine whether the program is legal and whether it can be carried.
Reporting the Findings
The evaluation has to end in a document the client can act on, not a list of observations.
- A Property Condition Assessment performed to ASTM E2018 is the standard commercial instrument. It produces a condition rating by system, an opinion of probable cost for immediate repairs, and a table of replacement reserves over a stated horizon — commonly 10 or 12 years.
- Findings are expressed as remaining useful life by system — roof, envelope, HVAC, elevators, electrical service — because owners budget against replacement years, not against adjectives.
- Immediate needs (life-safety violations, active water intrusion, structural distress) are reported separately from deferred maintenance, which can be scheduled against the capital plan.
The Reuse-Versus-New Comparison
The feasibility recommendation compares reuse against new construction on four axes, and cost alone rarely decides it:
| Axis | Favors reuse | Favors new construction |
|---|---|---|
| Cost | Structure and enclosure already exist and are already paid for | Extensive code upgrades, hazardous-materials abatement, structural strengthening |
| Schedule | Shell exists; entitlement often already in place | Concealed conditions drive change orders and delay |
| Program fit | Bay spacing, floor heights, and capacity suit the use | Program needs spans, heights, or loads the building cannot deliver |
| Non-financial | Historic tax credits, retained embodied carbon, community and brand value | Predictable performance and clean future adaptability |
Two items change answers often enough to memorize:
- Existing non-conforming zoning rights are frequently the most valuable asset in the building. A structure that exceeds today's height limit, covers more lot area, or sits inside today's setback may retain those rights if it is altered; demolishing it usually extinguishes them permanently, and the replacement must meet current zoning.
- Contingency must be set higher than for new construction. Renovation carries concealed conditions that no survey fully eliminates, so carrying a new-construction design contingency into an adaptive reuse budget understates the risk the owner is actually accepting.
A developer proposes converting two floors of a 1970s Group B office building into a Group A-2 restaurant and event space. Which pair of findings will most decisively govern feasibility?
An architect is beginning an evaluation of an existing building and is provided with a complete set of the original 1968 construction drawings plus a 1994 renovation permit set. What is the correct next step?
An owner will alter a primary function area on the second floor of a place of public accommodation. What accessibility obligation attaches to the path of travel serving that area?