What the ideal office-to-residential conversion looks like, and what makes a good deal

Almost every office building in Chicagoland can be converted to housing. That is the part most owners get backwards. Given enough money, you can cut courtyards into a floor plate, move a stair tower, and replace an entire curtain wall. The real question is whether the modifications a building requires still leave a deal that pencils, or whether you have spent so much reshaping the structure that you should have torn it down and built new.

That distinction is the whole game. As Chicago’s office conversion experts, we screen office assets across Northern Illinois and Southern Wisconsin, and the buildings that survive underwriting share a recognizable profile.

Start with the question that kills most deals: is the building overbuilt?

The first screen is not the floor plate. It is entitlement. Older office towers frequently contain far more floor area than current zoning would permit for a new residential building on the same site. That structure is a grandfathered entitlement, and reusing it captures density a ground-up project could never get approved.

Eugene Flotteron, AIA, Principal and Director of Architecture at CetraRuddy and the architect behind 25 Water Street, made this the opening move of his underwriting checklist when he joined us on The Real Finds Podcast to break down the largest office-to-residential conversion in United States history. He has converted buildings at 21 and 24 FAR and is working on one at 30 FAR, densities no new residential project could approach. An overbuilt building is not a problem to solve. It is the entire opportunity, and the gap between what exists and what you could entitle today is where conversion value comes from.

The Chicagoland version cuts two ways. In the Loop, the density delta is why distressed towers keep trading to conversion buyers. In suburban submarkets like Schaumburg, Naperville, and Arlington Heights, the grandfathered asset is usually site coverage and parking rather than vertical FAR.

Vacancy is the asset, not the liability

Conventional underwriting treats a vacant office building as distressed. In conversion underwriting, full vacancy is one of the most valuable conditions a building can have. A clear path to vacancy is the single biggest complexity in any conversion, and one tenant sitting mid-floor plate on a ten-year term can make a project impossible to phase.

An empty building lets the design team make aggressive structural moves. At 25 Water Street, the team cut two full courtyards out of the interior to bring light and air to the core, opened large portions of the facade, and added the lost area back on top. That level of surgery only works in an empty structure bought at a basis that can absorb it.

So the ideal candidate is fully vacant or has a short, clean runway to vacancy. A building at 60 percent occupancy with staggered expirations is the worst of both worlds. It does not produce enough income to justify holding, and it is not empty enough to convert.

The physical profile that actually converts

Building era is a clue rather than a rule, but the patterns hold. Pre-war buildings tend to be shallower, smaller, and easier to work with. Post-war and 1970s curtain wall towers carry a specific trap: many were designed on a five-foot office planning module that translates badly to apartments. Two modules give you a living room under ten feet wide. Three modules give you fifteen feet, which is generous but produces units running fifty feet deep. Solvable, but only by aligning unit layouts to the column grid.

The other physical variables that decide a deal:

• Window line. Punched window buildings with generous glazing convert far more readily than curtain wall towers with stingy openings. Light and air drive unit count.
• Floor plate depth. Roughly 30 to 45 feet from glass to core is the comfortable range. Deeper plates need light wells or courtyards, which is capital.
• Core position. Central cores work. Offset cores create dead corners that never become rentable.
• Floor to floor height. You need room for plumbing risers and drops under a slab never designed for wet stacks on every floor.
• Column spacing. Columns that land inside unit demising walls are free. Columns that land in the middle of a bedroom cost you a unit.

The 80 percent efficiency test

The number to underwrite to is efficiency, rentable area divided by gross floor area. Flotteron described a recurring developer threshold of roughly 80 percent per residential floor, below which deals stop working. Hitting that on a deep office plate usually means relocating stairs, removing surplus elevators, and cutting light into the core.

This is also where hidden value lives, because office buildings are loaded with infrastructure residential use does not need. On one project, right-sizing the elevator core produced 20,000 square feet of additional sellable area by replacing a bank of office elevators with a properly scaled scissor stair and the two elevators the residential program actually required. Below grade, surplus cellar space that would be prohibitively expensive to build new became parking.

When you walk a candidate building, look for what office use is over-provisioned. Excess vertical transportation, oversized mechanical rooms, and unused below-grade area are recoverable square footage and amenity space a ground-up project would pay full freight to create. At 25 Water Street, that produced roughly 100,000 square feet of amenities. The leasing pitch is not 400 square feet of apartment. It is access to the amenity floor.

What makes a good deal: basis, incentives, and speed

Three variables decide whether a good building becomes a good deal.

Basis: Conversions are bought out of distress for a reason. The reconstruction budget has to fit between acquisition cost and stabilized residential value, and there is no version where you pay a stabilized office price and make the numbers work. We track the distress pipeline daily on the RFP Chicagoland Commercial Real Estate Index, and we have written about individual repricings like 401 S. State Street selling out of distress and 105 West Adams hitting the market as a conversion play.

Incentives: Outside Manhattan, most conversions do not close the gap without public participation. Chicago’s LaSalle Street Reimagined program pairs Tax Increment Financing with an affordability requirement, and the first project broke ground at 79 W. Monroe with $28 million in TIF behind 117 mixed-income units. Suburban municipalities across Lake County and the collar counties increasingly have their own tools. Incentive alignment is not a nice-to-have in the Midwest. It is usually the deal.

Speed: You are carrying a vacant building through reconstruction, so conversion economics are engineered around velocity. Successful teams file early to start change of use approval, run separate demolition, structural, elevator, and window packages so trades start while design development continues, and buy long lead mechanical systems ahead of completed construction documents. Approval predictability matters as much as approval outcome, which is why markets without an as-of-right path see deals die on timing alone.

When the answer is industrial, or demolition

Residential is not always the highest and best use. A single-story suburban office on a deep site may be worth more as last mile industrial or as land, and low ceilings, deferred maintenance, and poor transit access all push toward ground-up redevelopment. Demolition is not a failure. It is often the move that unlocks the most value.

The screen, in one paragraph

The ideal office to residential conversion building is overbuilt relative to today’s zoning, fully vacant or nearly so, priced at distressed basis, punched window rather than curtain wall, roughly 30 to 45 feet deep from glass to core, structurally flexible enough to reach 80 percent floor efficiency, over provisioned with elevators and mechanical space you can reclaim, and located in a municipality with an incentive program and a predictable approval path. Miss two of those and you probably have a demolition candidate. Hit most of them, and you have the best risk-adjusted development opportunity in the market right now.

If you own or are underwriting an office asset in Chicagoland or Southern Wisconsin and want to know which category it falls into, our team runs this analysis from feasibility through execution. Reach Van Vlissingen and Co., Chicagoland’s oldest commercial real estate firm, at (847) 634-2300, explore our office conversion services, or follow the market on our blog and The Real Finds Podcast.