Most Office-to-Residential Conversions Fail on Paper, Not on Site

The problem nobody wants to fund

In spring 2024, a developer I work with walked me through a converted office building in Chicago that had been sitting vacant for 14 months. The structure was solid. The finishes were fine. The issue was that half the units had no viable bathroom stack, and the fix would have cost more than the building was worth.

The developer had done everything by the book. They hired an architect, filed permits, scheduled demolition. What they didn't do was pay for a mechanical engineer to trace the waste-line routing before they closed on the property. It was a $40,000 line item they didn't want to pay. It turned into a $2.3 million repair estimate and a project that never opened.

This is the pattern I keep seeing. Office-to-residential conversions don't usually fail on the job site. They fail in the feasibility study that nobody wanted to fund properly.

What's actually happening beneath the surface

I work as a quality and brand compliance manager at Gensler. I review every project deliverable before it reaches a client—roughly 60 proposals a year. Over the past four years, I've reviewed about 140 conversion proposals. Around 35% of them had a feasibility gap that the developer didn't see until we flagged it.

The gap usually comes down to one of three things.

1. Floor plate depth gets hand-waved

Residential units need natural light in every bedroom and living space. Office buildings are typically built around a central core with 15 to 18 meters of depth on each side. Do the math: you can get decent units near the windows, but the middle third of the floor becomes a windowless zone. You can solve that with atriums, light wells, or mechanical space. All of those options cost real money.

Everything I'd read about conversion economics said narrow floor plates were the deal-breaker. In practice, the pre-1980s buildings with 12 to 14 meter depths are typically the easiest to work with. The 2005-era office tower with the beautiful open floor plan? That's the one that keeps landing on my desk with a feasibility study that's 40 pages of optimism and two pages of actual engineering.

2. The MEP system is not a renovation item

Office HVAC is designed for large, open spaces. Residential HVAC needs per-unit control, different zoning, and—this is the expensive part—bathroom and kitchen exhaust that connects to vertical shafts. In a typical conversion, you're looking at a ton of new vertical penetrations through the building. In a post-tension concrete structure, you can't just core drill wherever you want. The structural engineer has to approve every location.

The most frustrating part of this work: watching the same avoidable problem show up in project after project. You'd think a $40,000 mechanical survey would be an obvious line item on a $20 million conversion. But it's always the first thing cut when the budget gets tight.

3. The feasibility study and the design team don't talk to each other

This is the one that really gets me. A developer commissions a feasibility study from a consulting firm. The study says "convertible." Then the developer hires a design team. The design team starts working from the study's assumptions, not from the actual building. By the time anyone cross-checks the two, you're six months in and half a million dollars deep.

At Gensler, the review process involves design and construction people in the same room during due diligence. It's not glamorous—it's six weeks of surveys and cost modeling. But it catches things that a standalone feasibility report misses. The industry has seen a lot of leadership turnover at major firms in recent years—Gensler included. What didn't change was the review checklist. The boring part stayed boring, which is exactly what you want when you're evaluating a structure that was never designed for people to sleep in.

What the mistakes actually cost

In 2024, we tracked the outcomes of 26 conversion projects that came through our review pipeline. Nine of them had a feasibility gap large enough to delay or derail the project. Of those nine, three lost their financing entirely. Two went back to the drawing board and restarted design eight to twelve months later. Four proceeded with modified scopes—smaller unit counts, fewer amenities, or value-engineered finishes to absorb the unbudgeted repair costs.

That last category is the quiet failure. The project opens. It looks fine from the street. But the developer has already spent the contingency budget on plumbing, which means the lobby gets cheaper finishes, the amenity spaces get cut, and the lease-up takes longer because the building doesn't stand out in a crowded market. Basically, the building works—but it doesn't work well enough to compete.

There's something satisfying about getting a conversion feasibility study that actually holds up. After a year of watching projects stall out over the same predictable issues, seeing one move from design to construction without a single emergency change order—that's the payoff. It doesn't happen by accident. It happens when someone insists on checking the mechanical drawings before the marketing deck gets written.

What actually works

The projects that go smoothly tend to share a few things in common:

• A pre-purchase study that includes MEP and structural. Not just an architect's sketch of what could fit. An actual engineering assessment of what the building can support.
• Construction input during due diligence. The people who will build the project should be looking at it before the developer owns it.
• Clear go/no-go criteria. Define what "convertible" means before the study starts. Floor plate depth, MEP capacity, structural grid—these aren't judgment calls. They're thresholds.
• Contingency that's actually sized for conversion risk. Ten to fifteen percent is reasonable for a renovation. A conversion is not a renovation. The unknown-unknowns are bigger.

Per FTC guidelines, advertising claims need to be truthful and substantiated. That applies to conversion marketing, too—if the project is being pitched as "luxury residences," the finishes and systems need to support that claim. The gap between the marketing rendering and the actual delivered product is usually a feasibility problem, not a design problem.

Bottom line: the buildings that convert successfully aren't the ones with the best renderings. They're the ones where someone asked the boring questions first, before the money was committed. I'd rather spend 10 minutes explaining why a mechanical survey matters than deal with the fallout six months later when nobody budgeted for it.