Thinking about adding an accessory dwelling unit to your Littleton property? You are not alone. With recent state and city updates, building an ADU is more straightforward than it used to be, and the potential uses are compelling for multi‑generational living or long‑term rental income. This guide breaks down what changed, the rules you need to follow, and how to move from idea to approved project with confidence. Let’s dive in.
What changed in 2025
State law now requires many Colorado cities, including Littleton, to allow one ADU on lots with a single‑unit detached home. The law also sets minimum protections for size, approvals, owner‑occupancy, and parking. You can review the statewide standards through the Colorado Department of Local Affairs’ ADU guidance for context. DOLA summarizes the statewide ADU rules and timelines.
Littleton adopted its own code update to align with state law. The city’s Unified Land Use Code was amended on June 3, 2025, and the ordinance is the controlling local source for ADU standards, approvals, and limits. You can read the ordinance text and staff materials for the exact language. See Littleton’s Ordinance No. 09, Series 2025.
Littleton ADU rules you must know
Where you can build
Littleton allows one ADU per lot in every zone where single‑family detached homes are allowed. ADUs can be internal, attached, or detached. Applications are reviewed by staff under objective standards, so most projects do not require a public hearing unless a property is in a designated historic district or has a landmark structure. Ordinance No. 09, Series 2025 explains where ADUs are permitted and how approvals work.
Size and height limits
Littleton caps an ADU at the gross floor area of the main house or 1,000 square feet, whichever is less. This is more generous than the state’s minimum safe harbor. Height depends on your zone and the height of the primary home. One‑story ADUs are allowed citywide, and two‑story ADUs are allowed when the primary home is two stories or more. The ordinance lays out size and height standards by zone.
Setbacks and placement
Detached ADUs are typically placed in rear yards. Setbacks and building coverage for an ADU cannot be more restrictive than for the primary home. Rear setbacks are often as low as 5 feet where applicable, and total building coverage must stay within your zone’s maximums. Always verify your lot’s exact numbers with planning staff. Check the ULUC standards in the city ordinance.
Parking requirements
In most cases, Littleton will not make you add new off‑street parking for an ADU. Exceptions apply if you have no existing off‑street parking, if your zone requires parking for the primary home, or if your block prohibits on‑street parking. Properties within a quarter mile of transit have special treatment in the code. Parking exceptions are detailed in the ordinance.
Owner‑occupancy and deed restriction
You generally cannot be forced to live on the property to build an ADU. State law limits owner‑occupancy requirements, with narrow exceptions. Before Littleton issues a building permit, you must record a deed restriction that says the ADU cannot be sold separately and the restriction runs with the land. See DOLA’s summary of statewide owner‑occupancy rules and Littleton’s ordinance for the deed restriction requirement.
Short‑term rentals are not allowed in ADUs
Littleton’s short‑term rental policy prohibits STRs in ADUs. You can rent an ADU long term if it meets all building and safety standards. Review the licensing rules before listing any unit for short‑term stays. Read Littleton’s STR rules.
How to get approved in Littleton
- Confirm zoning and eligibility. Use the city’s Zoning Portal or call Planning if you are unsure about your lot. Start with Littleton’s Zoning Portal.
- Do a quick pre‑application check. A short consult helps you flag setbacks, coverage, utilities, or historic status early. See the city’s ULUC updates and contacts.
- Finalize plans. Decide on internal, attached, or detached, and design to meet building, life‑safety, and zoning standards. State law also limits overly restrictive design requirements.
- Apply for permits and record the deed restriction. Littleton requires recording the deed document before issuing a building permit. Expect building, electrical, plumbing, and fire inspections during the project. The ordinance outlines permit steps and requirements.
- Pay fees and coordinate utilities. Impact fees and sewer tap fees apply per dwelling unit. Coordinate with your water and sewer provider and the fire district.
- Occupy or rent long term. Follow landlord‑tenant and licensing rules. Remember that short‑term rentals are not permitted in ADUs in Littleton. Review the city’s STR policy.
City contacts for quick help:
- Littleton Permit Center: 303‑795‑3751 or [email protected]
- Planning & Engineering (Planner of the Day): 303‑734‑8076 or [email protected]
HOAs and neighborhood rules
Colorado updated HOA law to prevent associations from banning ADUs where the state requires them to be allowed. HOAs can still apply reasonable, non‑prohibitive design conditions that do not unreasonably increase cost. Start by checking your CC&Rs and talk with the board early in your process. See the Division of Real Estate’s HOA guidance on ADUs and DOLA’s overview of statewide ADU rules.
Costs, fees, and financing options
Plan for standard building permit fees, impact fees, and sewer tap fees because each dwelling unit pays its share. Your designer or contractor can help map the line‑item costs alongside city schedules. If you are exploring financing, the state has resources that may support ADU programs in compliant cities.
DOLA launched the ADU Grant Program with cycles that began in 2025. The program funds local strategies such as pre‑approved plans, technical help, or fee relief in supportive jurisdictions. CHFA also works with ADU‑friendly financing options in coordination with state programs. Check current eligibility and whether Littleton is participating in any local incentives. Learn about the ADU Grant Program and related financing.
Common mistakes to avoid
- Skipping an early chat with Planning. A quick call can uncover setback quirks, nonconforming features, or parking issues that affect feasibility. Use the city’s ULUC and zoning resources.
- Underestimating permits and inspections. ADUs must meet building, electrical, plumbing, energy, and fire egress standards. Budget time for multiple inspections. The ordinance explains required codes and inspections.
- Missing the deed restriction filing. Littleton requires it before a building permit is issued. Build this step into your timeline. See the deed restriction requirement in the ordinance.
- Expecting short‑term rental income. ADUs cannot be licensed as STRs in Littleton. Confirm the STR prohibition.
Ready to map out an ADU that fits your goals and Littleton’s rules? Whether you want multi‑generational space or long‑term rental income, you will benefit from a clear plan and local guidance. If you want a second set of eyes on value, rental projections, or resale impact, reach out to Chad Goodale for a local, investor‑minded game plan.
FAQs
What are the key 2025 ADU changes in Littleton?
- Littleton now allows one ADU per lot in single‑family zones with administrative approval, a size cap up to 1,000 square feet, limited parking requirements, and a required deed restriction before the building permit issues. Read the ordinance.
How big and how tall can my Littleton ADU be?
- Your ADU can be up to the main home’s gross floor area or 1,000 square feet, whichever is less, with height tied to your zone and whether the primary house is one or two stories. See the ordinance standards.
Do I need to add off‑street parking for an ADU in Littleton?
- Usually no, unless you have no existing off‑street parking, your zone requires parking for the primary home, or your block bans on‑street parking. Parking rules are in the ordinance.
Can I short‑term rent my ADU in Littleton?
- No. Littleton prohibits short‑term rentals in ADUs, though long‑term rentals are allowed if you meet all code and safety requirements. Check the STR rules.
Do HOAs in Littleton still have a say over ADUs?
- HOAs cannot enforce restrictions that violate state ADU protections, but they can apply reasonable, non‑prohibitive conditions. Review your CC&Rs and talk with the board early. See the state’s HOA and ADU guidance.
What is the timeline for ADU approvals in Littleton?
- ADUs are approved administratively under objective standards, which can shorten timelines. Start with the Zoning Portal and a pre‑application chat to surface issues. Use the city’s ULUC and zoning resources.
Are there grants or financing options for ADUs in Colorado?
- DOLA’s ADU Grant Program supports local strategies in compliant jurisdictions, and CHFA offers financing pathways tied to those programs. Check current availability. Explore DOLA’s ADU Grant Program.
