ADUs And Coach Houses: What’s Allowed In Winnetka

Thinking about adding a coach house or renting an existing garage apartment in Winnetka? You are smart to check the rules first. Winnetka’s zoning is specific about what is allowed, and most new detached ADUs are not permitted today. In this guide, you will learn what counts as an ADU, what is allowed on your property, size and occupancy limits, and the steps to stay compliant. Let’s dive in.

What counts as an ADU or coach house

An accessory dwelling unit (ADU) in Winnetka is a separate dwelling located in an accessory building on a single-family lot. A “coach house” is an accessory structure that can contain up to two ADUs. These are controlled by the Village’s single-family zoning districts and related definitions in the code. You can review the Village’s ADU provisions in the Winnetka zoning ordinance on accessory dwelling units.

What is allowed today

Winnetka’s rules are centered on a key date. ADUs and coach houses are allowed only if the accessory building both existed and was constructed or used as a dwelling before March 20, 2012. The ordinance does not allow you to increase the number of ADUs beyond what existed or was occupied before that date. In practice, that means most new detached ADUs or new coach houses are not permitted today under the current code.

• Grandfathered only: If your coach house or garage apartment was a dwelling unit before March 20, 2012, you may keep or reestablish that use, subject to compliance.
• No new detached ADUs: Creating a brand-new detached ADU or converting a post-2012 accessory building is generally prohibited by the ordinance.

You can confirm the details in the Winnetka zoning ordinance on accessory dwelling units.

Size and occupancy rules

If your accessory dwelling qualifies under the pre-2012 rule, you still need to meet size and occupancy limits:

• Minimum size: At least 350 square feet for the first two occupants, plus 150 square feet for each additional occupant.
• Maximum occupancy: No more than seven persons per accessory dwelling unit.

These standards are spelled out in the Village’s ADU provisions.

Building and parking standards that still apply

Even when an ADU is allowed, accessory buildings must meet zoning and building standards that affect design and feasibility.

• Heights and setbacks: Accessory buildings have height limits tied to lot size. On lots under one half acre, they are limited to one story and 14 feet. On lots one half acre or more, they may be up to one and a half stories and 20 feet, with standard side and rear yard rules. See the accessory building height and setback rules for specifics.
• Parking: The code does not include a separate parking formula for ADUs in single-family districts. General accessory and garage rules apply, so it is smart to confirm requirements with the Village early.

Permits and registration: what you need

Before you occupy an ADU, you will need a certificate of occupancy. If construction or system work is involved, you will also need the appropriate building permits. Some older, lawfully registered units were excepted from new CO requirements when the ordinance was adopted, but you should verify your property’s status with the Village. Read more about certificate of occupancy and registration requirements and Title 15 building and life-safety codes.

• CO required: A certificate of occupancy is required before any ADU is occupied.
• Inspections: Expect building, life-safety, and fire compliance checks.
• Records matter: Village registration or historical permits can help document pre-2012 use.

If your structure does not qualify

If your accessory building did not exist as a dwelling prior to March 20, 2012, a new detached ADU will likely be denied under today’s rules. Your options are limited:

• Seek a variance, which can be challenging in single-family districts.
• Consider incorporating additional living space within the principal home under principal-dwelling rules.
• Monitor potential state-level changes that could alter local authority.

Buying or selling with a coach house

If you are evaluating a Winnetka property with a coach house or garage apartment, documentation is key. Ask for prior permits, certificates of occupancy, and any Village registration records that show the unit was constructed or occupied as a dwelling before March 20, 2012. Confirm unit size, occupancy, and code compliance. When listing, clarity about legal status protects your sale and builds buyer confidence.

Step-by-step checklist

Use this quick checklist to move forward with confidence:

1. Verify pre-2012 status. Check historical permits, COs, tax records, and photos. Ask the Village whether the unit was registered or recorded as a dwelling before March 20, 2012. The Village of Winnetka FAQs and contacts page is a good starting point.
2. Confirm how many ADUs existed pre-2012. You cannot increase the number beyond that point. See the ADU provisions in the zoning ordinance.
3. Measure the unit and plan occupancy. Meet the 350 square feet plus 150 square feet per additional person rule and the seven-person cap.
4. Apply for permits and a CO. Follow the Village’s certificate of occupancy and registration requirements.
5. Prepare for inspections. Ensure the structure meets Title 15 building and life-safety codes.
6. If nonconforming or seeking changes, discuss variances early with staff. Historical variance approvals exist in the code record, but each case is unique.

Watch for possible state changes

Illinois lawmakers introduced HB3552, the Local Accessory Dwelling Unit Act, in 2025. If enacted, it would limit a municipality’s ability to prohibit ADUs and could require faster local decisions. Until a state law passes and takes effect, Winnetka’s current ordinance controls. You can follow HB3552 in the Illinois General Assembly and regional context on Chicago ADU expansion for broader policy direction.

Ready to talk through a specific property or plan? For tailored guidance on buying or selling in Winnetka with coach house considerations, connect with Sondra Douglass for local, hands-on representation.

FAQs

Can you build a new detached ADU in Winnetka?

• Not under the current rules. New detached ADUs or coach houses are generally not allowed unless the accessory structure existed and was used as a dwelling before March 20, 2012, per the ADU provisions in the zoning ordinance.

What are the size and occupancy limits for a Winnetka ADU?

• The minimum habitable area is 350 square feet for the first two occupants, plus 150 square feet per additional occupant, with a maximum of seven persons per unit under the Village’s ADU rules.

Do you need a certificate of occupancy for an ADU in Winnetka?

• Yes. A certificate of occupancy is required before any ADU is occupied, and building permits are needed for construction work. Details are in the Village’s certificate of occupancy and registration requirements.

How tall can a coach house be in Winnetka?

• Height depends on lot size. On lots under one half acre, an accessory building is limited to one story and 14 feet. On lots one half acre or more, up to one and a half stories and 20 feet may be allowed. See the accessory building height and setback rules for details.

Who should you contact to verify an ADU’s status?

• Start with the Village’s Community Development and Building Department. The Village of Winnetka FAQs and contacts page lists how to reach staff and what documents you may need.

Could state law change Winnetka’s ADU rules soon?

• It is possible. HB3552 would limit local ADU bans if enacted. Until a new law takes effect, Winnetka’s current ordinance governs. You can follow HB3552 in the Illinois General Assembly for updates.