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Springfield, IL Accessory Structures: ADU Rules (2026)

Heavy Restrictions

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

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

Key Facts

Code Section: Zoning Ord. 155.068(b)(2)
ADU as dwelling: Prohibited - no detached accessory structure may be a dwelling unit
Max accessory height (residential): 18 ft
State preemption: None in force; IL HB 1813 pending, not enacted (2026)
Path to a second unit: Variance/text amendment via Planning & Zoning Commission

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 Illinois under recent ADU streamlining laws. The Springfield, IL rules below cover local size, height, and setback requirements.

Summary

Springfield's zoning code expressly prohibits using any detached garage, accessory building, or structure as a dwelling unit, so a freestanding accessory dwelling unit (ADU) is not permitted under Zoning Ordinance Section 155.068(b)(2). Illinois has no statewide ADU law in force (HB 1813 remains pending), so the local ban governs.

(b) In residential districts. (1) A detached garage, accessory building, or structure in a required rear yard shall not be less than three feet from any property line. On a corner lot, such garage, accessory building, or structure, shall be set back from the property line adjoining a side street the same distance as required for the principal building in the zoning district in which the garage, accessory building, or structure is located. (2) The maximum height allowed for any detached garage, accessory building, or structure in a residential zoning district is 18 feet. However, in no case shall any portion of a detached garage, accessory building, or structure be used as a dwelling unit or for any business or office use.

Source: Springfield, IL Code of OrdinancesView official code

Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Code of Ordinances: Supplement 82).

Full Breakdown

" Because Springfield's zoning ordinance does not establish an accessory-dwelling-unit (ADU) category and affirmatively bars residential occupancy of detached accessory buildings, a backyard cottage, coach house, or garage apartment as a separate dwelling is not allowed by right. 055) further constrain adding a second dwelling on a single lot. At the state level, Illinois has not enacted statewide ADU preemption: the proposed Local Accessory Dwelling Unit Act (HB 1813, 104th General Assembly) had only reached a second reading and was not signed into law as of mid-2026, so it does not override Springfield's local prohibition. Property owners seeking any residential second unit must pursue a zoning variance or text amendment through the Springfield Planning and Zoning Commission.

Violations & Fines

Using a detached garage or accessory building as a dwelling violates Section 155.068 of the Zoning Ordinance and is subject to the zoning penalty cross-referenced at Section 155.999, plus code-enforcement action requiring the unauthorized living space to be vacated, removed, or brought into a permitted use.

Frequently Asked Questions

Can I build a backyard ADU or coach house in Springfield, IL?

Not by right. Springfield Zoning Ordinance Section 155.068(b)(2) states that no portion of a detached garage, accessory building, or structure may be used as a dwelling unit, so a freestanding accessory dwelling unit is not permitted without a zoning variance or text amendment.

Does Illinois state law force Springfield to allow ADUs?

No. As of mid-2026 Illinois has no enacted statewide ADU law. House Bill 1813 (the proposed Local Accessory Dwelling Unit Act) had only reached a second reading and was not signed, so Springfield's local prohibition controls.

How tall can a detached accessory structure be in a Springfield residential district?

Up to 18 feet under Section 155.068(b)(2), but it can never be used as living space, a business, or an office.

Sources & Official References

Other rules in Springfield

Shed & Carport RulesSome Restrictions Garage ConversionsHeavy Restrictions Parking Rules: Abandoned VehiclesSome Restrictions Parking Rules: Snow Removal Parking RulesSignificant Restrictions Parking Rules: Loading ZonesSome Restrictions Fence Regulations: Retaining WallsSome Restrictions Animal Ordinances: Bird ProtectionHeavy Restrictions Landscaping Rules: Native PlantsLight Restrictions

All Springfield rules

How Springfield compares: Easiest Cities to Build an ADU·Compare Springfield to another location·View the Illinois accessory structures overview

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