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Paper 03: Houses a family can live in

Signed 1 October 2026.

Plank: Housing law should assume a family might have three generations in it, not just one, and should let people build and afford a house that fits.

What we want

A working family should be able to buy a house sized for however many people actually live in it, including a parent or grandparent or grown child who needs a place too, on one income, in a neighborhood where the ordinary errands of a day don't require a car. Today the law gets in the way twice. It zones most residential land so that only one household can occupy a lot no matter how big the house is, which makes a legal, self-contained space for a grandmother or an adult child hard to build even when the family can afford it. And it has let home prices climb so far past incomes that "one income" is no longer realistic in most of the country. We want the rules changed so a family can build the house it actually needs and pay for it with what one working adult earns.

The evidence

The median new single-family house completed in the United States in 2024 ran 2,146 square feet, according to the Census Bureau's annual survey of new construction [1]. American houses are not small by historical or international standards, and square footage is not the problem. The law caps how many separate households can legally occupy a lot, no matter how large the house on it is. Under most codes, a 2,146-square-foot house can hold a grandmother's bedroom and bathroom. What it usually can't do, because of zoning rather than construction cost, is become two legal dwellings: a main house and a small second unit. With two legal dwellings, a widowed parent or a young married child can have a lockable door of their own without sharing one kitchen and one budget.

That restriction is close to universal. A national survey of zoning codes covering more than 1.37 billion acres and 174 million residents found that single-family homes can be built by right, meaning without asking anyone's permission, on about 95 percent of residential land, while housing with more than one unit on it is allowed by right on only 12 percent [2]. California's Othering and Belonging Institute ran a full audit of every municipal zoning code in the state and found that 95.8 percent of the state's residential land is zoned for single-family housing only [3]. This is not a coastal-city problem or a blue-state problem; it is close to the default setting for the American lot.

The affordability side of the claim is real and gets worse, not better, when checked. In 1970, the median-priced home cost 2.3 times the median household income. By 2024 that ratio had risen to roughly 5 times income (5.1 by this calculation, using National Association of Realtors sale-price data and Census Bureau income data), matching Harvard's Joint Center for Housing Studies, which independently put the ratio at 5.0 in 2024, tying the prior record set in 2005 [4][17]. A ratio near 2.3 is roughly what a family can carry on one income with a conventional mortgage. A ratio above 5 generally requires two full incomes, a large down payment from savings or family money, or both.

Families have already begun adapting to this the way people adapt to a rule they can't change: they double up. Eighteen percent of Americans lived in a multigenerational household in 2021, up from 7 percent in 1971, and the increase is sharpest among young adults: a quarter of Americans aged 25 to 34 lived multigenerationally in 2021, versus 9 percent in 1971, according to Pew Research Center [5]. People are already choosing the arrangement the law makes difficult to build for.

Two other culprits are often named, and the honest answer is not the same for both. On institutional investors buying up single-family homes: nationally, large institutional owners (defined by the Government Accountability Office as those holding at least 1,000 homes) own roughly 2 percent of the single-family rental stock, and in 2024 the great majority of investor purchases, 59 percent, came from small investors owning ten properties or fewer, with the largest investors' share falling that year [6][7]. Nationally, this is not the main driver of the affordability problem. But it is not nothing everywhere: in metro Atlanta, institutional investors own about 30 percent of the single-family rental stock, roughly ten times the national rate, and in some Atlanta suburbs corporate ownership tops 70 percent of a neighborhood [8]. The honest statement is that this is a serious, geographically concentrated problem rather than a national one, which argues for capping it before it spreads rather than treating it as the main cause of the national price-to-income ratio.

On parking and land: a lot dedicated to two mandatory off-street parking spaces per unit, which is standard in most zoning codes, is land that can't hold a second bedroom, a second unit, or a small business. Since 2017, at least two dozen U.S. and Canadian cities have dropped their parking minimums entirely, starting with Buffalo in 2017 and including Minneapolis's unanimous 2021 vote and Anchorage's unanimous 2022 vote [9].

Why it happened

The legal foundation for single-family-only zoning is a single Supreme Court case: Village of Euclid v. Ambler Realty Co., decided in 1926. The Court upheld a municipality's right to zone out anything but detached single-family homes from most of its land, and Justice George Sutherland's opinion described apartment buildings in single-family neighborhoods as "parasite[s]" that fed off the residential character built by the houses around them [10]. That language set the tone for the next century of American land-use law: multi-unit housing was treated as a threat to be zoned away from single-family neighborhoods rather than a normal form of housing to be built where families wanted it. Cities wrote that judgment into code, lot by lot, for the next hundred years, and the codes have mostly not been rewritten since.

Parking minimums arrived by a separate but related route, written into most zoning codes from the 1950s through the 1970s as the automobile became the assumed mode of travel; they took residential land that could have held a second unit or a small store and required it to hold cars instead, with no relationship to how many cars a given household actually owned.

On price: the run-up from a 2.3 to a 5.1 ratio is not one law but a long stretch of supply constrained by the zoning above, meeting demand pushed up by cheap credit and population growth in a small number of desirable metros, over five decades.

What to change

Federal. Give multigenerational households a tax code that recognizes them rather than penalizing them: a credit for the added cost of housing and caring for a parent, grandparent, or adult child under one roof. Two bipartisan bills already move in this direction and are worth watching as the live legislative template: the Multigenerational Home Caregiver Credit Act, from Senators Peter Welch (D-VT) and Rick Scott (R-FL), would give a $2,000 annual credit to an adult who houses and cares for an aging relative [11]; the Multigenerational Family Tax Credit Act of 2026, from Representative Luz Rivas, would credit 50 percent of home modification costs for a multigenerational household, up to $8,000, for households under a $200,000 income cap [12]. Canada has run a similar credit since 2023, covering 15 percent of the cost of building a secondary suite for a senior or disabled relative, up to $7,500 [13], a working example, not a hypothetical. On institutional owners, the federal ask has largely already happened: the 21st Century ROAD to Housing Act became law on July 11, 2026, without the President's signature, under the Constitution's ten-day rule. It bars any institutional investor owning 350 or more single-family homes from buying more, with exceptions for build-to-rent and renter-to-owner programs; the prohibition takes effect January 7, 2027, carries penalties up to $1 million or three times the purchase price, and sunsets after 15 years unless Congress renews it [14]. That's the mechanism this paper argues for. The remaining work is watching the build-to-rent exception, which is broad enough to become the way large owners keep growing their single-family holdings under a different label, and renewing the cap before it sunsets.

State. Publish a state pattern book: a set of house plans, including plans for a main house with a small attached or detached second unit, that are pre-approved for code and structural compliance so a family doesn't have to pay an architect and wait months for a plan review on a design the state has already seen a hundred times. California has already moved in this direction: a 2024 law (AB 1332) required every city to adopt a pre-approved ADU plan program by January 2025, and a second bill (AB 1206), still moving through the legislature as of this writing, would extend pre-approval to single-family and multifamily housing generally, with large jurisdictions required to comply by mid-2026 and smaller ones by 2028 [15]. California's approach leaves each city to adopt its own plan library rather than publishing one statewide book. A genuine statewide pattern book, available to any builder or family in any city in the state without a separate local approval fight, would go further. Alongside it: pass a free-range childhood law on the model Utah adopted in 2018, which amended the state's child-neglect statute to say that letting a child walk to school, play outside, or stay home alone unsupervised is not, by itself, neglect [16]. A multigenerational household with a grandparent or older sibling nearby needs the law to recognize that supervision does not require an adult's constant physical presence; Utah's law was written for exactly that judgment.

Local. Kill the parking minimum. A city does not need to mandate two off-street spaces per unit to have enough parking; it needs to stop mandating that spaces be built whether or not anyone needs them, which is what Buffalo, Minneapolis, and Anchorage have already done [9]. And let the corner store come back: reopen the zoning category, eliminated in most cities during the mid-twentieth-century push to separate residential and commercial uses, that allows a small grocery, bakery, or shop inside a residential block. Under most current codes, an existing corner store is grandfathered in until it closes, at which point the space can never legally become a store again: a one-way ratchet against neighborhood-scale commerce that a single zoning amendment could reverse.

What a bill would do

A model state bill would do three things, each load-bearing on its own. First, direct the state housing agency to publish and periodically update a statewide pattern book of pre-approved house and accessory-unit plans, available to any jurisdiction or builder in the state at no design cost; a jurisdiction that adopts a plan from the book must issue a permit within a fixed number of days without a separate design review, since the point is removing the delay and expense of a second review of a plan the state has already vetted. Second, amend the state's child-neglect and child-endangerment statutes to state explicitly that unsupervised independent activity by a child of sufficient age and maturity (walking to school, playing outside, being left briefly home alone) is not neglect on its own. Third, create a state tax credit mirroring the federal caregiver and home-modification credits, so a family in a state without a state income tax large enough to make the federal credit matter still has a state-level offset for the cost of building or maintaining a multigenerational household. None of the three requires a city to change its zoning map against its will; all three make the legal multigenerational house cheaper and faster to build once a city chooses to allow it.

What would prove us wrong

If, after ten years of parking-minimum repeal and pre-approved pattern books in the cities and states that adopt them, the share of new construction that includes a legal second unit or multigenerational suite does not rise relative to comparable cities that kept the old rules, the zoning theory of the problem is wrong and something else (construction cost, labor supply, land price independent of zoning) is the binding constraint. If the price-to-income ratio keeps climbing in cities that have adopted pattern books and killed parking minimums at the same rate as cities that haven't, the reforms aren't reaching the part of the market that sets prices. And if, five years after the 350-home institutional cap takes effect, institutional investors' share of the single-family rental stock in concentrated metros like Atlanta keeps rising rather than leveling off, the build-to-rent exception has become the loophole this paper warned about, and it needs to be closed by name.

Sources

  1. U.S. Census Bureau, "Characteristics of New Housing," 2024 data: median floor area of completed single-family houses, 2,146 square feet. https://www.census.gov/construction/chars/highlights.html

  2. National Zoning Atlas, analysis published by New America, "Where Is Multi-Family Housing Actually Allowed in America?", April 2026 snapshot. https://www.newamerica.org/insights/where-is-multi-family-housing-actually-allowed/

  3. Othering & Belonging Institute, UC Berkeley, statewide California zoning study, 2024: 95.8 percent of California residential land zoned single-family only. https://phys.org/news/2024-05-staggering-california-residential-zoned-family.html

  4. Housing Almanac, compiling National Association of Realtors median existing home sale price and U.S. Census Bureau Current Population Survey median household income: price-to-income ratio 2.3 in 1970, 5.1 in 2024. https://housingalmanac.com/affordability

  5. Pew Research Center, "The Demographics of Multigenerational Households," March 24, 2022, and "Young Adults in U.S. Are Much More Likely Than 50 Years Ago to Be Living in a Multigenerational Household," July 20, 2022. https://www.pewresearch.org/social-trends/2022/03/24/the-demographics-of-multigenerational-households/ ; https://www.pewresearch.org/short-reads/2022/07/20/young-adults-in-u-s-are-much-more-likely-than-50-years-ago-to-be-living-in-a-multigenerational-household/

  6. U.S. Government Accountability Office, "Rental Housing: Information on Institutional Investment in Single-Family Homes," GAO-24-106643, May 22, 2024. https://www.gao.gov/products/gao-24-106643

  7. Realtor.com 2024 investor purchase data, reported in HousingWire, "Investor home sales hit record high as small buyers gain ground." https://www.housingwire.com/articles/2024-investor-home-sales-small-large-buyers-realtor-com/

  8. Atlanta Journal-Constitution, "Data: Investors now own 30% of metro Atlanta's single-family rental homes." https://www.ajc.com/news/atlanta-news/data-investors-now-own-30-of-metro-atlantas-single-family-rental-homes/CNP7ATXIBJDVDMDQ6RRSGVUGZI/

  9. Parking Reform Network mandates map, reported in NextSTL, "Eliminating Parking Minimums Works. Ask Minneapolis and Buffalo," and Planetizen, "New Map Compiles Parking Reform Efforts Nationwide." https://nextstl.com/2024/01/eliminating-parking-minimums-works-ask-minneapolis-and-buffalo/ ; https://www.planetizen.com/news/2024/05/129143-new-map-compiles-parking-reform-efforts-nationwide

  10. Village of Euclid v. Ambler Realty Co., 272 U.S. 365 (1926). https://supreme.justia.com/cases/federal/us/272/365/

  11. Office of Senator Peter Welch, "Welch and Scott Introduce Bipartisan Bill to Create New Multigenerational Home Caregiver Tax Credit." https://www.welch.senate.gov/welch-and-scott-introduce-bipartisan-bill-to-create-new-multigenerational-home-caregiver-tax-credit

  12. H.R. 7584, Multigenerational Family Tax Credit Act of 2026, 119th Congress, introduced by Rep. Luz Rivas, February 13, 2026. https://www.congress.gov/bill/119th-congress/house-bill/7584

  13. Canada Revenue Agency, "Multigenerational home renovation tax credit (MHRTC)." https://www.canada.ca/en/revenue-agency/services/tax/individuals/topics/about-your-tax-return/tax-return/completing-a-tax-return/deductions-credits-expenses/line-45355-mhrtc.html

  14. National Association of Realtors, "21st Century ROAD to Housing Act," and CNBC, "What 21st Century ROAD to Housing Act means for homebuyers and sellers," became law July 11, 2026, without the President's signature. https://www.nar.realtor/advocacy/road-to-housing-act ; https://www.cnbc.com/2026/07/11/21st-century-road-to-housing-act-homebuyers-sellers.html

  15. California Building Officials, "Pre-Approved ADU Plans" (AB 1332, jurisdictions required to adopt an ADU pre-approval program by January 2025). https://www.calbo.org/post/pre-approved-adu-plans ; California AB 1206, "Single-family and multifamily housing units: preapproved plans," as amended in the Senate August 18, 2025 (large jurisdictions by July 1, 2026, small jurisdictions by January 1, 2028). https://leginfo.legislature.ca.gov/faces/billNavClient.xhtml?bill_id=202520260AB1206

  16. Utah S.B. 65, "Child Neglect Amendments," signed by Gov. Gary Herbert, effective May 8, 2018. https://letgrow.org/utah-free-range-parenting-law/

  17. Harvard Joint Center for Housing Studies, "The State of the Nation's Housing 2026" (home price-to-income ratio of 5.0 in 2024, tying the record set in 2005). https://www.jchs.harvard.edu/son-2026-price-to-income-map