Office-to-residential conversions cost up to $268/sq ft to retrofit, and buildings that exceed this threshold become stranded assets worth less than their conversion cost

Cities like New York, Chicago, and London are aggressively incentivizing office-to-residential conversions to address both office vacancy and housing shortages. NYC developers are on track to start 9.5 million square feet of conversions in 2026, more than double the 4.3 million square feet started in 2025. However, deep retrofit costs can reach $268 per square foot (in London), and when the total conversion cost exceeds the post-upgrade residential value, the building becomes economically stranded -- too expensive to convert, too obsolete to lease as office space, and too costly to demolish. Why it matters: When a building is stranded, it sits vacant and deteriorating while the owner continues paying property taxes, insurance, and minimum maintenance, so the building becomes a blight on the surrounding neighborhood, so adjacent property values decline, so the city loses both property tax revenue and the potential housing units that conversion would have created, so the affordable housing shortage in the downtown core persists, so workers commute from distant suburbs and the transit system loses off-peak ridership revenue, so public transit service is cut, so the downtown becomes even less attractive. The structural root cause is that most office buildings constructed between 1960 and 1990 have deep floor plates (70+ feet from window to core) designed to maximize office density, but residential units require natural light within 30 feet of a window, so the interior floor area of these buildings is physically unusable for housing without cutting light wells or atriums that add enormous cost -- and no amount of zoning reform or tax incentives can change the fundamental geometry of the existing structure.