ADU Guide for Ithaca
What you need to know to build an accessory dwelling unit in Ithaca, NY.
Understanding ADUs in Ithaca
In May 2025 the City of Ithaca adopted an ADU ordinance that allows these units in several zones, giving homeowners a new way to add housing.
An ADU is a smaller, self-contained home on the same lot as a main house. It can be attached — in a basement, attic, addition or garage — or detached, like a cottage or carriage house. Every ADU must meet the building code's safety rules. The city is also working on its own ADU guide and pre-approved template plans.
Zoning & Requirements
R-1 Zone
Low-density residential. Lots usually 6,000 sq ft or more. Attached and detached ADUs allowed.
R-2 Zone
Medium-density residential. Lots usually 4,000 sq ft or more. More room to choose placement.
R-3 Zone
Higher-density residential. Lots usually 3,000 sq ft or more. The most flexible rules.
Not sure of your zone? Check the official City of Ithaca zoning map.
View Zoning MapMaximum Size
800 sq ft
Largest allowed building footprint
Setbacks
5–10 ft
Side and rear distances vary by zone; front usually lines up with the house
Height
2 stories / 20 ft
No taller than two stories or 20 feet
Parking
0–1 space
Often reduced or waived, especially near transit
Lot Coverage
Up to 40%
House and ADU together must stay within the zone limit
Owner Occupancy
May apply
The owner may need to live in the house or the ADU
Other things to check
- Historic districts may require design review
- Flood zones need special permits and raised construction
- Tree protection rules can affect where you build
- Water, sewer and power capacity must be confirmed first
Permits & Approval
Approval usually takes about 4–8 weeks, depending on how complex the project is.
- 1
Pre-Application Meeting
Review your lot and idea with the Planning Department.
- 2
Submit Application
Turn in site plans, drawings and fees.
- 3
Plan Review
The city checks zoning and building code compliance.
- 4
Permit Issued
Once approved, construction can start.
- 5
Inspections
Scheduled checks during the build.
- 6
Certificate of Occupancy
A final inspection clears the unit for move-in.
Design Considerations
Site Planning
Entry, privacy, utilities and how the unit relates to the house.
Floor Plan
Smart layouts get the most out of limited square footage.
Accessibility
Step-free, universal design works for every stage of life.
Energy Efficiency
Good insulation and heat pumps cut monthly bills.
Financing Your ADU
Home Equity Loan
Borrow against the equity you already have.
Construction Loan
Short-term funding that becomes a mortgage when done.
Cash-Out Refinance
Refinance and pull out equity to fund the build.
ADU Programs
Some lenders offer loans made for ADU projects.
ADU Property Visualizer
Property type
ADU placement
A freestanding cottage behind the house gives the most privacy — great for renters or multigenerational living.
Stay Informed
Updates on Ithaca ADU rules, design tips and finished projects.