If you Googled "how much do door dashers make" and ended up here, I have bad news: I'm an architect, not a gig-economy analyst. But if you searched for "gensler office to residential conversion" because you're trying to figure out whether an office building can become housing, you're in the right place. I'm a project manager at Gensler, and for the last six years I've led more than 40 conversion feasibility studies, many of them on absurd deadlines. The honest version of what I've learned is simple: there is no universal answer. There are three scenarios, and your building belongs to one of them.
When I first started doing these studies, I assumed the key variable was vacancy rate. That seemed logical: empty offices should become apartments. Three projects later, I realized vacancy rate matters less than the physical building. A Gensler architect will usually start by measuring the distance from the exterior glass to the core, not by sketching unit plans. The real variables are floor-plate depth, window-to-wall ratio, structural grid, and the age of the mechanical systems. The "just convert it" thinking comes from an era when office floor plates were 10,000 square feet and buildings had more perimeter windows. Today, a lot of office buildings have 30,000-square-foot floors, low slab heights, and sealed facades. That's not a renovation—it's a building-type transformation.
The three scenarios
Most conversion questions fit one of three buckets. The mistake is treating them like one problem with a single gold-plated answer. They aren't.
Scenario A: Shallow floor plates and real windows—the straightforward candidate
If your floor is less than 50 feet from window to core and the perimeter glazing is at least 30 percent of the facade, you're in the easiest scenario. This is often a 1970s or 1980s building with smaller floors and operable windows—or at least windows that someone can actually see out of.
In this scenario, you can move fast, but you still need to respect the budget drivers. Plumbing risers are usually the biggest cost: new kitchens, bathrooms, vent stacks, and water lines. The second-biggest line item is often the unit entry assembly. Door trim might sound cosmetic, but in a conversion it's a fire separation. The gap between the unit door frame and the drywall is exactly where smoke travels in a corridor fire. A rated door frame with intumescent seals and proper door trim isn't a decoration; it's an egress requirement.
Counterintuitive advice: don't choose color tiles until you've surveyed the slab flatness. Offices often have concrete slabs with subtle slopes or old leveling compound that's delaminating. If the floor isn't flat, large-format tile can fail quickly. I learned this the hard way. On a 2024 conversion, we specified 24-by-24 porcelain color tiles for a lobby corridor. I assumed the slab was flat because the structural drawings showed a concrete slab. Didn't verify. The floor had a 1.25-inch slope from the original drainage layout, and the tile job came up hollow. That cost $14,000 in demolition and re-setting. Now we require a floor-flatness survey before any tile specification. It's the kind of mistake you learn once.
Also, don't ignore the mailbox and parcel locker plan. According to USPS Business Mail 101 (pe.usps.com/businessmail101), a flat can measure up to 12 inches by 15 inches, so your mail slot or parcel locker needs to accommodate that. I want to say the exact USPS requirement is in the Postal Operations Manual, but don't quote me on that—verify with the local postmaster before you finalize the storefront design.
Scenario B: Deep floor plates and sealed facades—change the program, not the building
If your building is 120 feet wide with a 30,000-square-foot floor and small perimeter windows, conventional apartments are probably a bad fit. This is the scenario where people waste the most money. They try to force 60-foot-deep units, and the interior spaces end up dark, awkward, and hard to sell.
My team's recommendation is usually to change the program, not the building. Consider co-living or student housing: shared kitchens and living rooms can sit in the windowless core, while bedrooms stay at the perimeter. Senior housing can work the same way: common dining and activity spaces in the middle, resident rooms at the glazing. This is a harder conversation to have with a lender, but it's more honest than pretending the floor plate doesn't matter.
If you really need conventional apartments, you'll need to introduce interior light wells or atriums. That means cutting openings through the structural slab—a significant engineering effort. In March 2024, a client called at 4:30 p.m. needing a feasibility ruling before a purchase option expired on Monday. Normal turnaround for our structural review is three weeks. We found a structural engineer who could review the as-built drawings overnight, paid a $3,500 rush fee on top of the $18,000 base fee, and delivered our recommendation by Sunday. The client's alternative was losing a $2.2 million option. The answer was yes, but the atrium construction would extend the schedule by 14 months.
For deep-floor-plate buildings, light-colored materials matter more than people think. Lighter color tiles and high-reflectance finishes in corridors can reduce the cave effect and make circulation more usable. But that should come after the structural decision, not before. Per FTC's Green Guides (ftc.gov), if a material is labeled "recyclable" but most residents don't have access to a recycling program for it, that's a compliance problem. Don't accept unqualified sustainability claims on tile or trim without asking where the recycling actually happens.
Scenario C: Medium floors and an older frame—the phased conversion
This is the "maybe" scenario. You have a 1960s or 1970s building with a 15,000-to-20,000-square-foot floor, a straightforward concrete frame, and moderate window access. You don't have the budget to gut the entire building, and you don't need to convert every floor at once.
This is where an office-to-residential conversion becomes a phased play. Start with the lower floors, which have easier egress and closer access to lobby services. Keep the upper floors as office for now. This works in cities with strong retail and weak office demand. But there's a hidden trap: the corridor-to-unit junction. A phased conversion creates a temporary interface between active office floors and residential floors. That junction has to be fire-rated in both directions. If you shorten the schedule and rush the compartmentation, you'll pay for it during inspection.
Don't try to save money by reusing existing office doors as apartment entry doors. This was true 10 years ago, and it's still true today: office doors are usually not rated or tested for residential unit entry assemblies. A solid-core wood door might look fine, but fire-door ratings are not a currency you can invent. If the door doesn't have a label, it doesn't count. Use a rated frame, proper hinges, and the right door trim to close the assembly. It's not the prettiest part of the project, but it's the one that keeps a building inspection from stopping you right before move-in.
How to tell which scenario you're in
You can usually classify a building in under an hour if you have the plans. Here's the quick test:
- Measure the distance from the perimeter glazing to the structural core. Less than 50 feet: Scenario A. Between 50 and 80 feet: Scenario C. More than 80 feet: Scenario B.
- Check the window-to-wall ratio. If less than 25 percent of the facade is glazing, treat it as Scenario B even if the floor plate is shallow.
- Look at the structural ceiling height. If you have less than 9 feet from finished floor to structural soffit, every duct run and door header becomes a coordination problem. This is where a small detail like door trim becomes a schedule issue.
- Find the column grid. Residences work well with unit widths of 12 to 20 feet. If the columns are 30 feet apart, the floor plate can still work, but the framing is heavier and the cost goes up.
If you're not sure, get a short feasibility call with a Gensler architect. We treat it as an intake, not a sales pitch. Bring your floor plans, a recent rent roll, and the age of the mechanical systems. We'll tell you if it's worth studying—and if it isn't, we'll say so. Knowing what we don't design is part of being a specialist. I'd rather work with a client who wants honesty than one who wants a confident wrong answer.
A quick word on urgency: I've handled rush studies with fees as small as $3,000 and as large as $150,000. The ones that fail are almost always the ones where someone tried to skip the triage. When I'm coordinating a fast-track review, 80 percent of the battle is having the right as-built drawings and the right structural engineer—not faster sketching. If your lender needs an answer by Friday, don't hire an architect to start drawing on Monday. Do the feasibility check first, even if it means paying rush fees. It's cheaper than drawing a building that can't be built.
The renderings of converted office buildings are beautiful, but the real work is unglamorous. It's floor slop, fire-rated door trim, mailbox dimensions, and contractor reality. If you know your building's scenario, you can make the right call before you spend seven figures on drawings. That's what I tell every client: the answer is in the building, not in the brochure.
