Thinking about creating space for a parent, adult child, or caregiver without moving out of the neighborhood? In Lisle, an accessory dwelling unit can be a practical way to live close while preserving privacy. The village allows ADUs, but the rules are tailored to true multi‑generational living rather than open rentals. In this guide, you’ll learn exactly what Lisle permits, the costs to expect, how to permit and finance a project, and smart design choices for aging in place. Let’s dive in.
What Lisle allows for ADUs
Where ADUs are allowed
Lisle defines an accessory dwelling unit as a smaller, independent home on the same lot as a main residence. ADUs are allowed as accessory uses to a detached house, duplex, or townhouse. You can confirm the definition and allowed use in the village’s zoning code for accessory dwelling units. Review the Village of Lisle ADU regulations.
How you can create one
You can create an ADU in two ways in Lisle: by converting existing interior space or by building an addition attached to the primary home. The addition must connect to the living area and not just to an attached garage. Detached backyard cottages are not authorized in the ADU section of the code. The village also allows a separate exterior entrance to the ADU, but that door may not face the street. See the ADU section for creation methods and design notes.
Occupancy and ownership rules
Lisle’s program is designed for multi‑gen living. The code requires:
- Owner occupancy of either the main home or the ADU.
- Familial occupancy of the ADU. Only persons related to the primary household may live in the ADU.
- Age or disability condition. At least one of the two units must be occupied by a person age 55 or older or by a person with a physical or developmental disability for whom joint occupancy is medically necessary or beneficial.
These rules make ADUs a great fit for intergenerational arrangements and caregiver support rather than short‑term or general market rentals. Check the village code for full occupancy details.
Why ADUs fit multi‑gen living in Lisle
If you want to help an older parent stay close, give an adult child independent space, or house a caregiver, an ADU can work well under Lisle’s framework. The 55+ or disability occupancy condition and the family‑only rule align with these goals. This focus also tends to limit speculative investor interest, which can benefit households seeking stability and support. Review the occupancy provisions in the code.
Choose the right ADU type
Interior conversion
Converting a basement, attic, or part of the main floor into a separate unit is often the most cost‑effective path. Interior projects typically have less site work, fewer exterior changes, and can move through permitting more quickly. See how Lisle defines and permits ADU conversions.
Attached addition
Building an attached one‑bedroom or suite can create more independence and make accessibility easier. For aging in place, plan for a ground‑floor bedroom and full bath, wider doors, and a step‑free entry. The village’s permit guides outline submittal requirements for additions so you can design with compliance in mind. Use the Building Permit Guides to plan your submittal.
Accessibility features to prioritize
Because at least one unit must be occupied by a person 55+ or with a qualifying disability, consider universal design from day one:
- Zero‑step entry or a gently sloped ramp
- Wider hallways and doorways
- Lever handles and non‑slip flooring
- A curbless shower and grab‑bar blocking These choices improve safety and comfort and can reduce future retrofit costs. The village’s permit guides are a good starting point for code‑aligned planning.
Plan your budget
Actual costs vary by size, finishes, and systems work, but these ranges can help you set expectations:
- Interior conversions often run from the tens of thousands into the low six figures, depending on plumbing, electrical, and egress needs. See national context on small‑home build costs.
- Attached additions commonly land in the low‑to‑mid hundreds of thousands based on square footage and structural work. Prefab examples elsewhere show base prices starting around the mid‑$90Ks, but those figures usually exclude site work and permits. Review a prefab cost example for context.
For a Lisle property, get bids for both an interior conversion and an attached addition so you can compare scope, timeline, and value.
Permits, timeline, and parking
Permit steps and documents
Lisle offers pre‑application meetings through Development Services, which can save time. Typical submittals include a site plan, existing and proposed floor plans, elevations for additions, structural details, mechanical, electrical and plumbing plans, and energy documentation. Start with the Building Permit Guides.
Fees and timing
Permit fees are based on project valuation with flat minimums and separate trade permits. Budget for building, electrical, plumbing, mechanical, and plan review fees. Timelines vary; interior conversions usually move faster than additions. Check the village’s Development Fees page.
Parking requirements
Lisle’s off‑street parking schedule sets minimums for residential uses, and additional spaces may be required depending on how the ADU is classified for parking purposes. Verify expectations during your pre‑application meeting. Review the off‑street parking chapter.
Financing, income, insurance, and taxes
Financing options
Common ways to pay include cash, a home equity line or loan, or renovation mortgages such as FHA 203(k), where eligible. If you plan to count rental income to qualify, ask lenders early about rules and documentation. Fannie Mae and FHA have pathways to consider ADU income in some cases, though requirements differ by program. See Fannie Mae’s guidance on rental income and FHA updates discussed here. Note that Lisle’s family‑only occupancy rules may limit practical rental income scenarios.
Insurance and utilities
Tell your insurer before you convert or add a unit. Coverage limits, liability, and endorsements may need to change, especially if a relative will pay rent or a caregiver will live on site. If you plan separate utility meters or systems, confirm requirements with the village and your utility providers. Use the village permit resources to coordinate early.
Property taxes and value
Adding living space typically increases assessed value and taxes. ADUs can add market value by improving function for multi‑gen living, but tax impact varies. Check with the DuPage County assessor or a local appraiser for estimates. Learn more about how additional units can affect value and policy.
Resale considerations in Lisle
Because owner‑occupancy, family occupancy, and the 55+ or disability condition run with the code, future buyers will inherit these obligations. That can narrow appeal for investors, but it is a strong positive for households seeking multi‑gen flexibility. Focus on well‑designed, accessible layouts, quality finishes, and a clean permit history. Review the occupancy rules that shape resale.
A step‑by‑step roadmap
- Confirm your zoning and eligibility, and ask the Zoning Administrator about any constraints or variance options.
- Schedule a pre‑application meeting with Development Services to review parking, utilities, and submittal needs. Use the village guides to book and prepare.
- Compare concepts and bids for an interior conversion versus an attached addition. Ask your lender about financing and whether any ADU income is usable for your scenario. See Fannie Mae’s rental income guidance.
- Prepare and submit your permit package. Budget permit fees using the village’s valuation schedule. Check the Development Fees page.
- Design for aging in place up front to avoid costly retrofits later.
Ready to map your options and run numbers for your Lisle address? Reach out to Dimpi Mittal for a thoughtful, local plan that fits your family and your budget.
FAQs
Can I build a detached backyard ADU in Lisle?
- No. Lisle’s ADU rules allow only interior conversions or additions attached to the home, not standalone backyard cottages. See the ADU section of the code.
Who is allowed to live in a Lisle ADU?
- Only persons related to the occupants of the primary unit may live in the ADU, and either the ADU or the main home must be owner‑occupied. One of the units must house a person 55+ or someone with a qualifying disability. Review occupancy rules.
Do I need extra parking for an ADU in Lisle?
- Possibly. The village’s off‑street parking schedule sets minimums for residential uses, and applicability to an ADU is determined by the Zoning Administrator. Check the parking chapter.
How many ADUs can I have on one Lisle lot?
- One. Only a single ADU is allowed per detached house, duplex, or townhouse. See the ADU regulations.
Can I rent a Lisle ADU to non‑relatives or use it for short‑term rentals?
- No. The code requires family occupancy and owner occupancy, which prohibits renting to unrelated tenants or operating it as a short‑term rental. Review the ADU section.
How long does permitting take for an ADU in Lisle?
- Timelines vary by scope and workload. Interior conversions usually move faster than additions. Plan for plan review, permit issuance, and inspections over several weeks to months. Start with the Building Permit Guides.
Will adding an ADU raise my property taxes in Lisle?
- Likely yes. Added living area usually increases assessed value and taxes. Check with the DuPage County assessor for a property‑specific estimate. Read more on value impacts.
