Share scarce land
Two or four households can share land that zoning otherwise reserves for one.
02
Missing middle
Bring back the homes between a house and a high-rise
Duplexes, fourplexes, cottages, courtyard apartments, and rowhouses once made ordinary neighborhoods work. Let them belong again.
In plain English
Allow a house-sized building to contain more than one home, and restore familiar forms such as duplexes, courtyard apartments, and rowhouses.
How it works
Remove the barrier. Let homes respond.
Broaden the builders
Smaller projects can be undertaken by local builders and homeowners.
Create gradual change
Neighborhoods can add homes one lot at a time instead of relying only on megaprojects.
The implementation test
Real reform or paper promise?
Missing-middle reform is not a mandate for every block to become high-rise. Most projects remain small and appear gradually as owners choose to build.
TestStrongWeak or symbolic
Housing types
StrongDuplexes through fourplexes and townhomes are clearly legal.
Weak or symbolicOnly one narrow prototype technically qualifies.
Lot rules
StrongUnit count fits within a practical building envelope.
Weak or symbolicPer-unit lot area or setbacks make added homes impossible.
Cost
StrongFees and utility rules reflect the project's small scale.
Weak or symbolicEach unit pays charges designed for a new detached house.
Strong policy principles
- Allow the housing types by right in every residential district.
- Reduce minimum lot sizes and per-unit lot-area rules.
- Use form rules that fit the envelope rather than micromanaging unit count.
- Do not require a separate parking space for every home.
Watch for
- Large minimum lots
- Owner-occupancy mandates
- Per-unit fees
- Rules that allow a duplex but make it physically impossible
Pair it with
- Pre-approved building plans
- Small-builder financing
- Anti-displacement property-tax relief
- Accessible design incentives
Measure whether it works
- Projects by housing type
- Net homes added
- Small-builder participation
- Geographic distribution of permits
In practice
What this reform looks like on the ground.
Portland, OregonMajor provisions effective August 1, 2021; expanded July 2022
Residential Infill Project
Portland legalized duplexes, triplexes, fourplexes, and other middle-housing options, then expanded the package in a second implementation step.
Lesson
Real reform often arrives in stages. Portland first opened the door, then widened it.
Evidence status
Portland Residential Infill Project ↗ (opens in a new tab)The ordinances establish what Portland legalized and when. The Auckland and multi-city studies supply the broader evidence about how substantial capacity reforms affect construction.
Raleigh, North CarolinaAugust 2021 through August 2022
Stepped missing-middle reform era
Raleigh followed its ADU reform with missing-middle legalization, citywide parking reform, and a second middle-housing and transit-oriented package.
Lesson
A city does not have to solve everything in one vote. Raleigh kept removing barriers as it learned what still stood in the way.
Evidence status
Raleigh adopted text changes ↗ (opens in a new tab)Raleigh's adopted text changes document the sequence. Its public Missing Middle tracker reports which projects followed, while broader studies address effects beyond one city.
Why support it?
The evidence behind the solution.
Established evidence
Scarcity turns neighbors into bidders.
When more households want in than there are homes available, the highest bidders win. Everyone else pays more, accepts less, moves farther away, doubles up, or leaves.
Keep in mind: Construction costs, incomes, interest rates, amenities, and migration matter too. Housing supply is not the only force—it is the part local policy can directly obstruct or enable.
Strong evidence
A city cannot build homes it has made illegal.
Legalize real projects across enough land and builders respond. Auckland did this at city scale and saw a large permitting boom; narrower reforms have usually delivered less.
Keep in mind: Permission is necessary but not sufficient. Financing, land, construction costs, approval time, and demand determine whether newly legal homes are actually built.
Strong evidence
Legal on paper is not the same as buildable in practice.
A reform can promise density and still bury it under tiny maps, parking ratios, setbacks, fees, hearings, and delay. Good reform makes ordinary projects legal, feasible, and predictable.
Keep in mind: Chicago's narrow reform produced no detectable building increase in its early years. That helps show why scale, feasibility, and follow-through matter.
Figure 2 · Living space after upzoning
The strongest post-reform increases appear after roughly five years, especially for large upzonings.
REDRAWN FROM STUDY DATAFigure 2 · Living space after upzoning
| Years relative to upzoning | All upzonings | Large upzonings | Small upzonings |
|---|---|---|---|
| −4 | -1 | -2 | 0 |
| −3 | 0 | -1 | 0 |
| −2 | -1 | 0 | -1 |
| −1 | 0 | 0 | 0 |
| 0 | 0 | 0 | 0 |
| +1 | 0 | 1 | 0 |
| +2 | 1 | 2 | 1 |
| +3 | 2 | 4 | 1 |
| +4 | 3 | 6 | 2 |
| +5 | 5 | 9 | 3 |
| +6 | 6 | 11 | 4 |
| +7 | 7 | 13 | 5 |
| +8 | 8 | 15 | 5 |
| +9 | 9 | 16 | 6 |
Figure 6 · Estimated treatment effects on dwelling permits
The estimated effects become positive after the reform for both attached and detached homes.
REDRAWN FROM STUDY DATAFigure 6 · Estimated treatment effects on dwelling permits
| Years relative to reform | All dwellings | Attached | Detached |
|---|---|---|---|
| −4 | -0.05 | 0 | -0.02 |
| −3 | 0 | -0.02 | 0 |
| −2 | 0.02 | 0 | 0 |
| −1 | 0 | 0 | 0 |
| 0 | 0.1 | 0.05 | 0.04 |
| +1 | 0.25 | 0.15 | 0.1 |
| +2 | 0.45 | 0.3 | 0.15 |
| +3 | 0.75 | 0.55 | 0.2 |
| +4 | 1.15 | 0.85 | 0.28 |
| +5 | 1.45 | 1.05 | 0.35 |