Why Lake Forest's Coach Houses Still Answer to a 2014 Ordinance, Not a 2026 Bill

What does it actually mean when a Lake Forest listing mentions a coach house with "guest suite or income potential"? If you have been comparing suburbs this year, you have probably also seen headlines about a new Illinois housing bill that would let homeowners build multiple units on a single residential lot. It is easy to assume the two are connected, that the accessory dwelling unit behind that shingled colonial on Green Bay Road is now governed by a fresh statewide standard. It is not. The bill that would have done that stalled in Springfield this year, and the rule that actually applies to a Lake Forest coach house today is one the City Council passed more than a decade ago, under much narrower terms.

That gap between what buyers assume and what is actually on the books is worth understanding before you write an offer on a property where the accessory structure is part of the appeal.

The Ordinance Already on the Books

Lake Forest's estate-era housing stock has a history most other North Shore suburbs do not share in quite the same way. Many of the city's larger properties were originally built with separate living quarters for domestic staff, chauffeurs, groundskeepers, the kind of household that a Gold Coast fortune once required on-site. Over the following decades those units fell out of use and, in many cases, out of legality, as zoning codes caught up with a suburb that no longer ran on live-in staff.

The city reversed course in 2014. Illinois REALTORS reported that the City Council voted unanimously to allow greater use of accessory dwelling units in certain zoning districts and under specific circumstances, following a template set two years earlier when the Village of Winnetka adopted its own liberalized ADU ordinance. The North Shore-Barrington Association of Realtors testified in support of the change, arguing it would give older adults and adults with disabilities a way to stay near family while keeping their own space, among other benefits. Lake Forest was described at the time as the latest municipality to formally recognize what its housing stock had quietly been built for a century earlier.

Lake Forest's zoning code is the rule that governs a Lake Forest coach house right now: local, specific to certain zoning districts, and considerably more conservative than the standard many buyers think already exists statewide.

The Bill That Would Have Changed That

In February 2026, Governor JB Pritzker used his State of the State address to introduce the Building Up Illinois Development plan, a package of bills aimed at a housing shortage the administration pegs at roughly 142,000 units statewide. The Illinois General Assembly's texts of HB5626 and its Senate companion, SB4071, proposed requiring every Illinois municipality to permit accessory dwelling units in any zoning district that allows single-family homes, with no additional requirements for lot size, setbacks, design review, or owner occupancy beyond what a single-family home already faces.

The bill went further than simple ADU legalization. BillTrack50's summary of HB5626 describes a proposed sliding scale for how much housing a single lot could hold:

• Lots up to 2,500 square feet: at least one detached single-family unit
• Lots between 2,500 and 5,000 square feet: up to four dwelling units
• Lots between 5,000 and 7,500 square feet: up to six dwelling units
• Lots over 7,500 square feet: up to eight dwelling units, including cottage clusters

For scale, a typical Lake Forest lot in many of the city's established neighborhoods well exceeds 7,500 square feet. Under the bill as introduced, that could have meant a legal path to eight units on a single parcel, a dramatic departure from Lake Forest's 2014 ordinance,

Where the Bill Actually Stands

According to Capitol News Illinois, by July 2026 the plan had not moved. Despite the legislature's own deadlines for advancing bills, HB5626 and its companion measures remained stuck, with only a nonvoting Senate Executive Committee hearing to show for months of advocacy on both sides. The report quoted Illinois Municipal League CEO Brad Cole, testifying against the package, as saying: "the core issue for us is the preemption of local authority, and that also means the preemption of local input."

Supporters have not given up. Illinois REALTORS framed the package as one of the most significant housing policy shifts the state has attempted, and the administration has continued pushing components of it through the session. But as of this writing, none of it is law. The sliding-scale unit counts, the removal of owner-occupancy requirements, the statewide override of local zoning discretion, all of it exists only as proposed legislation that home-rule municipalities like Lake Forest have actively lobbied against.

What This Means If You're Comparing a Coach House Across Suburbs

If you are touring estates in Lake Forest, Lake Bluff, or elsewhere on the North Shore and a listing highlights a coach house or accessory structure, the question worth asking is not what the state might eventually allow. It is what the city currently permits on that specific parcel, in that specific zoning district, under an ordinance that has been in force since 2014 and has not been rewritten since.

That distinction matters in a few concrete ways.

An existing, legally permitted coach house on a Lake Forest property already cleared a bar that many neighboring suburbs never lowered. Because Lake Forest's ordinance predates the current statewide fight by over a decade, a property with a documented, compliant accessory unit represents settled value rather than speculative upside. That is different from a listing that gestures at "potential" for a unit that does not yet exist, where the buyer would need to confirm zoning eligibility before assuming anything about rental income or multigenerational use.

The reverse is also true. A buyer who assumes the pending state standard already applies, and prices in the ability to add a coach house or a second unit on a lot where Lake Forest's current ordinance would not allow it, is working from a rule that does not yet exist. Any assumption about future flexibility should be treated as exactly that, an assumption, not a fact to build a purchase decision around.

For sellers, this is also a moment worth understanding rather than assuming. A property with a documented, code-compliant accessory dwelling unit is not interchangeable with one where an owner simply mentions "potential." The first is verifiable. The second depends on a legislative outcome nobody can currently guarantee.

A Few Questions Worth Asking Before You Write an Offer

Is the accessory unit on this property currently permitted, or does the listing describe potential that has not been confirmed with the city? Lake Forest's Community Development Department can confirm whether a specific parcel's zoning district and lot configuration qualify under the 2014 ordinance.

If the statewide bill eventually passes, would it apply retroactively to properties already built out under the local rule, or only to new applications? That is a question for the city's planning staff once and if the legislation advances further than a committee hearing.

Does the presence of an existing ADU affect how the property is assessed or taxed? That is a separate conversation worth having with a tax professional, since accessory structures can affect a property's classification independent of any zoning question.

If a coach house, guest suite, or accessory structure is part of what draws you to a specific Lake Forest property, it is worth understanding which rulebook actually governs it before that detail becomes part of your offer. The Kim & Carleigh Team works these questions through Jameson Sotheby's International Realty's Lake Forest office every week, matched with the same design-first eye we bring to staging and presentation. Schedule a design-forward consultation and we will walk the specific parcel with you, zoning district and all, before you make a decision on what that accessory space is actually worth.

This article is general information, not legal, tax or financial advice. Consult a qualified professional about your situation.