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Allen County, IN Accessory Structures: ADU Rules (2026)

Some Restrictions

Compiled from the official code textEditor Martyn O'NeillLast verified July 2026

ADU rules in Allen County, IN, also called accessory dwelling unit regulations or granny flat ordinances, cover setbacks, owner-occupancy, parking, and permit requirements.

Key Facts

Governing code: Allen County Zoning Ordinance, Title 3
ADUs per lot: One
Integrated ADU minimum: 300 square feet
Freestanding ADU: If no integrated ADU
Enabling statute: IC 36-7-4

ADU Eligibility Quick-Check

An Accessory Dwelling Unit (ADU) is a smaller, independent living unit on the same lot as a single-family home: converted garages, detached cottages, basement or attic conversions, and attached additions all qualify. Most states have streamlined ADU permitting since 2020, but local rules still control size, height, and setback.

Is your lot zoned single-family or multi-family residential?
Does your lot have at least 1,200 sq ft of buildable space?
Is your existing home owner-occupied (in most states this is not required, but some require it for ADU permits)?
Will the ADU stay under your state's size cap (commonly 850-1,200 sq ft for detached)?
Can you provide one off-street parking space (waived in many states within 0.5 mi of transit)?

If you answered 'yes' to most of these, you likely qualify in Indiana under recent ADU streamlining laws. The Allen County, IN rules below cover local size, height, and setback requirements.

Summary

In unincorporated Allen County, the Zoning Ordinance allows one accessory dwelling unit (ADU) per residential lot. An integrated ADU inside a single-family home must be at least 300 square feet, and only one freestanding ADU is permitted where there is no integrated unit.

These county ordinances apply to unincorporated areas of Allen County. Incorporated cities within the county may have their own rules that take precedence over county-level regulations.

If integrated into a single family detached dwelling, and if there is no freestanding accessory dwelling unit on the property; the integrated accessory dwelling unit shall be at least 300 square feet.

View official code

Full Breakdown

The Allen County Zoning Ordinance (Title 3), administered by the Fort Wayne-Allen County Department of Planning Services, treats accessory dwelling units as a residential accessory use. A lot may have one primary single-family detached dwelling plus either one Type III manufactured home or one freestanding accessory dwelling unit, provided there is no integrated ADU on the lot. If instead the ADU is integrated into the single-family home, it must be at least 300 square feet. Inside Fort Wayne, New Haven, and other incorporated towns the city's own zoning controls; these rules govern the unincorporated county.

Violations & Fines

Building or occupying an ADU without an Improvement Location Permit, or a second freestanding dwelling where one is not allowed, is a zoning violation enforced by Planning Services with correction orders and fines.

Frequently Asked Questions

Can I build a backyard apartment in unincorporated Allen County?

Yes, one freestanding accessory dwelling unit is allowed on a residential lot if there is no integrated ADU. Get an Improvement Location Permit from the Department of Planning Services first.

How small can an integrated ADU be?

An accessory dwelling unit integrated into a single-family detached dwelling must be at least 300 square feet under the Allen County Zoning Ordinance.

Sources & Official References

Other rules in Allen County

Fence Regulations: Height LimitsSome Restrictions Shed & Carport RulesSome Restrictions Garage ConversionsSome Restrictions Tiny HomesSome Restrictions Fence Regulations: Material RestrictionsSome Restrictions Fence Regulations: Retaining WallsSome Restrictions Fence Regulations: Neighbor Fence RulesSome Restrictions Fence Regulations: Fence Permit RequirementsSome Restrictions Animal Ordinances: Wildlife FeedingSome Restrictions

All Allen County rules

How Allen County compares: Easiest Cities to Build an ADU·Compare Allen County to another location·View the Indiana accessory structures overview

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ADU Rules in Cities Across Allen County

Fort Wayne, IN