Residential
ADUs Are Adding Rental Supply, But Construction Costs Cap the Upside
By Real Estate Wire Staff, . Real Estate Wire.
Accessory dwelling units, the backyard cottages and garage conversions built on existing residential lots, are moving from a niche workaround to a recognized piece of housing policy across the United States, according to Propmodo. In California, ADUs accounted for roughly one in four new housing structures built last year, and in Los Angeles and San Francisco, more ADU permits were issued than for all other housing types put together.
The economics can work for individual homeowners. Propmodo profiled Elaine Yang, an urban planner in Irvine, California, who rents a 540-square-foot prefab cottage in her backyard for $3,000 a month against a $1,600 loan payment, buying the unit from Samara, a company that builds standalone backyard structures with full kitchens, bathrooms and separate entrances. Yang told Propmodo she sees it as a long-term investment that could eventually house her parents.
New York moved to formalize ADU production under former Mayor Eric Adams, and his successor Zohran Mamdani has pushed the approval process faster, with city officials projecting 25,000 new units over 15 years through the City of Yes initiative. The Department of Buildings has taken in hundreds of permit applications, more than half originating in Queens, where single-family lots and detached houses make conversions more feasible than in denser boroughs. A city pilot loan program offering up to $395,000 per project drew more than 2,800 applications in 2025 before closing, and when it reopened it was sized for just 25 homeowners per year, a gap that illustrates how far demand outstrips available support.
Arizona, Washington and other states have loosened ADU restrictions at the state level, and Congress has approved grants to help municipalities adopt preapproved unit designs, reducing the permitting friction that slows individual projects. Data from Austin, Nashville, Charlotte and Denver, cited by Propmodo, shows affordability improved in those markets following ADU reforms, though the units remain a small share of total housing production in each city.
The constraint that keeps showing up is construction cost. Propmodo puts the range at roughly $200,000 for a garage conversion up to $550,000 for a fully custom build with parking. At those figures, the math only works for homeowners who already have equity, access to financing and a market where rents are high enough to service the debt. That profile fits coastal California and parts of New York far better than it fits most of the country.
The scale problem is stark in New York. The 25,000 units projected over 15 years represent a fraction of the 700,000 units city planners say the market needs over the next decade. Experts quoted by Propmodo acknowledge ADUs cannot close that gap on their own; the argument for them is that they add supply in markets where any new rental unit puts at least marginal pressure on rents.
On that point, the Bureau of Labor Statistics data for August 2026 is worth noting: rent of a primary residence was up 2.7 percent year on year, while owners equivalent rent rose 3.1 percent over the same period. Both figures remain above the overall consumer price increase of 3.4 percent for the same month. ADU supply is not large enough to move those numbers materially, but the direction of rent growth reinforces why policymakers are reaching for every available tool, including ones that add supply one backyard at a time.
What the reporting does not establish is how many of the ADUs being permitted are actually reaching completion and entering the rental market, as opposed to stalling mid-project when financing or contractor availability falls through. That completion rate is the number that would tell investors and policymakers whether the policy momentum is translating into real supply.
Source: https://propmodo.com/backyard-units-gain-traction-as-partial-answer-to-housing-crunch/
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