Homeowner’s Guide: Zoning & ADUs
Backyard cottages, garage apartments, basement units, in-law suites. Whatever you call them, we understand homeowners want the flexibility to build an accessory dwelling units on their properties. But before you think about design or financing, there’s one question that trumps the rest: what does your local zoning code allow?
What is an ADU?
An accessory dwelling unit (ADU) is a second, smaller home on the same lot as a main house. It has its own living space, kitchen and bathroom, and it shares the lot, so the land isn't subdivided and the main house stays in place.
ADUs usually take one of three forms:
Detached: a standalone cottage, or a unit above a detached garage
Attached: an addition that shares a wall with the main house
Internal: a converted basement, attic or part of the existing house
People build them for rental income, to house a family member or caregiver, or to downsize while staying on their own property.
Can I build an ADU on my property?
Your city, town or county's zoning code decides whether an ADU is allowed on your property, and under what conditions. Rules can differ between neighboring towns, and even between zoning districts in the same town. Some states have passed laws requiring local governments to allow ADUs in more places, but local codes still set many of the details.
Rules that commonly apply to ADUs
Whether ADUs are allowed at all in your property's zoning district
How they're approved. Some districts allow ADUs by right, with no public hearing. Others require a hearing or special permit.
Attached or detached. Some codes allow one type but not the other.
Owner occupancy. The owner may be required to live in either the main house or the ADU.
Who can live there. Some codes limit ADU residents to family members or older adults.
Parking. Some codes require an extra off-street parking space for the ADU.
Size and placement. Limits on floor area, height, and distance from property lines (setbacks).
Why are these rules so hard to find and understand?
Zoning codes weren't written for quick answers. Finding the rules for a single property usually means:
Finding your zoning district on your jurisdiction’s zoning map, then checking for overlay districts that might add or change rules
Locating the right sections of a code that can run hundreds of pages
Checking for amendments adopted since the code was last published
Interpreting legal language like definitions, tables, and cross-references to other sections
Missing one requirement can mean redrawing plans or re-starting an application.
How can Land Use Labs help?
We designed Parcel Reports to summarize the zoning rules for an individual property in plain language. Enter an address, and the report brings together the property's zoning district, allowed housing types, dimensional requirements like setbacks and height limits, and parking rules — everything you need to begin planning for your new ADU.