Chicago City Council approved the Additional Dwelling Unit ordinance in 2020 and created five pilot areas. In September 2025, the Council expanded the ordinance beyond those pilots so more addresses can add a unit. The code splits ADUs into two kinds. A conversion unit is inside the existing building, such as a basement or an attic. A coach house is a detached structure on the same lot.
Official pages: Department of Housing ADU program · eligibility · requirements · zoning map
ADUs were common in the first half of the twentieth century. The city says construction was prohibited starting in 1957, when zoning added parking rules and banned secondary residential structures. The amended code opens that door again, with a pre-certification before any permit.
Where an ADU is allowed now
The municipal code allows ADUs by right in all multi-unit residential districts and in certain business and commercial districts. A single-family RS-1, RS-2, or RS-3 lot can add an ADU only if it sits in an ADU-Allowed RS Area. Those areas are created by City Council ordinance under section 17-7-0754. Some of them add extra limits.
Do not use the old “R1 through R5” label as a yes. Pull the pin on the zoning map, then check the eligibility map. Lakefront, landmark, and planned-development overlays can still constrain the design even when the base district allows an ADU.
Before you buy:
- Confirm the district and whether an RS lot is inside an allowed area
- Read any block cap or owner-occupancy limit on that area
- Check open violations on the Department of Buildings portal
- Count the legal units already on the lot
How many units you can add
The Department of Housing states these counts:
| Existing legal units | Conversion units | Coach houses |
|---|---|---|
| 1–4 | One | One |
| 5–7 | Two | One |
| 8–10 | Three | One |
| 11–13 | Four | One |
A conversion requires the principal building to be at least 20 years old. One coach house can be added even if the principal building is newer, but the principal building must exist first. On a brand-new house, the coach house comes after the main building, not before it.
The city’s own example: a property with four existing units, principal building from 2005, may add one conversion unit and one coach house.
No extra parking stall is required for these ADUs. That is a direct change from the parking rules that helped shut coach houses down in 1957.
Floor area, height, and setbacks are still lot-specific. They live in the zoning ordinance and in plan review, not in a single citywide square-foot slogan. Design to the parcel. Do not assume a number you saw on an old summary.
Owner-occupancy is not one citywide switch
If an ADU-Allowed RS Area has an owner-occupancy rule, and the principal building is a detached house, the owner must occupy that house to get pre-certification. The rule covers both conversion units and coach houses. If the owner does not live there when you apply, the application does not qualify. Proof is a government photo ID plus one of: a recent tax bill or exemption record, a current utility bill, a recorded deed, a mortgage statement, or the declarations page of the homeowner policy.
Multi-unit districts that allow ADUs by right are a different path. Read the area limits before you tell a seller that every Chicago bungalow can take an investor coach house. Some can. Some cannot, until the owner lives in the front house.
Block caps, short-term rentals, and affordability
Certain ADU-Allowed RS Areas cap how many conversion units and coach houses, combined, can be pre-certified on the same block in one calendar year:
- RS-1: one pre-certification per block
- RS-2: two
- RS-3: three
Short-term leases and vacation rentals, including Airbnb, are not allowed in conversion units. The same ban applies to coach houses built after 2021. A DSCR exit needs a long-term lease, not a nightly rental, on those units.
When the owner adds two or more ADUs, in any mix of conversion and coach house, 50% of the new units, rounding down, must be restricted as affordable for 30 years. Rent them to households at or below 60% of area median income. The owner picks which units carry the restriction. Register each affordable ADU with the Department of Housing. The registration fee is $500 per affordable ADU. Record the affordability covenant with the Cook County Clerk, and file an annual compliance affidavit. Details are on the city’s affordability page.
A coach house also carries a labor rule. The general contractor and the subcontractors must participate in Registered Apprenticeship Programs approved by the U.S. Department of Labor’s Office of Apprenticeship.
If the project needs an administrative adjustment, the Department of Planning and Development charges a $500 fee for that process.
Detached coach houses behind vintage Chicago bungalows and two-flats are the most common investor ADU type in neighborhoods like Portage Park, Belmont Cragin, and South Shore.
Coach house vs. conversion ADU
| Type | Best for | Typical cost (2026) |
|---|---|---|
| Detached coach house | Wide lots, alley access | $180K–$280K |
| Basement conversion | Bungalows with high basements | $80K–$150K |
| Attic conversion | Two-flats and three-flats with sufficient headroom | $70K–$130K |
| Rear addition | Deep lots in R3–R5 zones | $120K–$200K |
Permitted ADU square footage adds to ARV on refinance — unpermitted work fails appraisal and blocks DSCR exit at 5.75%–10.5%.
Financing a Chicago ADU project
Most ADU builds require acquisition-plus-construction capital before generating rent:
| Phase | Product | Rate band |
|---|---|---|
| Buy distressed SFR + ADU build | Hard money / fix-and-flip | 8.99%–13.5% |
| Stabilized (primary + ADU leased) | DSCR cash-out or rate-and-term | 5.75%–10.5% |
Worked example: Portage Park bungalow + coach house
| Line item | Amount |
|---|---|
| Purchase (distressed bungalow) | $285,000 |
| Coach house construction (permitted) | $195,000 |
| All-in cost | $480,000 |
| Post-ADU appraised value | $620,000 |
| Primary unit rent | $2,100/mo |
| ADU rent | $1,650/mo |
| Combined rent | $3,750/mo |
| DSCR at 75% LTV, 7.25% | ~1.12 |
Program links: fix and flip loans Chicago · hard money lenders Chicago · DSCR loans Chicago · rehab loans for investment property
PadSplit and room rental — separate from ADUs
Investors searching PadSplit Chicago or shared room-rental models should treat them as separate from ADUs and STR. PadSplit rents individual rooms — often triggering:
- Zoning — rooming house / shared housing classifications vary by ward; many residential zones prohibit rooming-house use
- Building code — egress, fire separation, and occupancy limits per Chicago building code
- Chicago SDRO — tenants staying 30+ days trigger landlord-tenant rules under the RLTO
- Financing — lenders underwrite permitted use; illegal rooming configurations fail DSCR refi
Do not model PadSplit gross income until zoning and building code confirm the use is legal.
Permit path the city actually uses
The ADU process page puts Department of Housing pre-certification ahead of the building permit. A pre-certification letter does not authorize construction.
- Check eligibility and area limits
- Apply for Department of Housing pre-certification and upload the documents that fit the lot
- Hire a licensed architect or structural engineer
- File a plan-based building permit with the Department of Buildings, and attach the approval letter
- Revise the plans if review sends corrections, then pay the permit fee
- Build with licensed contractors and call inspections
- Certificate of occupancy is required for buildings of four or more units. For a one- to three-unit building or a coach house, the city says you may request one before inspections
Budget several months for plan review on a detached coach house. Do not promise a tenant a date until the permit is issued. Unpermitted work fails a later appraisal and blocks a DSCR exit at 5.75%–10.5%.
Investor checklist before closing
- Zoning confirmed on the eligibility map, including any RS-area cap or owner-occupancy rule
- ADU design fits size and setback limits
- Budget includes permit fees, utility connections, and contingency
- ARV pro forma includes both primary and ADU rent
- Exit financing pre-qualified — pre-qualify with Jaken Finance Group
- RLTO compliance plan if tenant stays 30+ days
Related: ADU construction loans · short-term rental laws hub · top 5 cities to build ADUs · why are ADUs so popular · submit flip
Example: two new units and the affordability cut
Example only. Not a quote.
A legal two-flat in an allowed district is under four existing units, so the table allows one conversion and one coach house. That is two new ADUs. Half of two, rounding down, is one. One of the two new units must be the affordable unit for 30 years, at or below 60% of area median income, if both are built. The registration fee on that affordable unit is $500, plus the recording cost at the Cook County Clerk.
| Line | Amount |
|---|---|
| Purchase of the two-flat | $340,000 |
| Basement conversion | $95,000 |
| Coach house | $210,000 |
| All-in cost | $645,000 |
| Illustrative as-completed value | $820,000 |
| 75% of that value | $615,000 |
If the file qualifies for 100% of cost, the 75% value cap is lower, so the loan sizes to $615,000, not $645,000. The sponsor brings the $30,000 gap plus closing costs. Fix-and-flip and construction pricing stays in 8.99%–13.5%. A complete fix-and-flip file closes in 7–10 business days. New construction timing is often 10–14 business days. After both units are leased on long-term leases, a DSCR refinance runs 5.75%–10.5% and about 14 business days, with up to 80% loan-to-value on a cash-out for qualified borrowers in select markets.
Model the affordable unit at the restricted rent, not at a market studio rent. If the restricted rent misses the payment, the hold fails even when the coach house leases quickly.
What to confirm before you wire a deposit
- Eligibility map says yes for this address, including any RS-area limit
- Owner-occupancy, if the area requires it on a detached house
- Building age of at least 20 years if you need a conversion
- Block cap still has room this calendar year
- Affordable-unit count if you are adding two ADUs
- Apprenticeship plan if you are building a coach house
- No Airbnb assumption on a conversion or a post-2021 coach house
- Scope, comps, and liquidity for fix and flip in Chicago
Run the address on the eligibility map before you price a coach house. Then pre-qualify the construction file. Related reading: Chicago coach house financing and Chicago two-flat financing.
Rates, terms and conditions offered only to qualified borrowers and are subject to change at any time without notice. Closing times are in business days and commence upon satisfaction of borrower conditions. All loans are subject to full underwriting for loan approvals. Jaken Finance Group only finances non-owner occupied investment properties.
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