Louisville allows a detached accessory dwelling unit by right on most single-family lots. Here is exactly what the code permits — size, setbacks, parking, and owner-occupancy — each point cited to the adopted regulations.
Every figure below is drawn from Louisville's adopted ADU regulations. The exact setbacks for your parcel depend on its zoning — the planner reads them off your lot.
Permitted by right
Yes
Approved through the normal building-permit process — no discretionary hearing.
Maximum size
Up to 800 sq ft
Detached ADU ≤ 800 sf; attached ADU ≤ 1,000 sf. An ADU may not exceed 75% of the primary house's floor area (or the maximum allowed square footage), whichever is less — but an ADU of at least 500 sf is allowed in all cases. Detached height ≤ 25 ft (attached = same as the primary house). Landmark, deed-restricted-affordable, or accessible ADUs may go to 1,000 sf detached / 1,200 sf attached. City of Louisville ADU regulations (eff. June 23, 2025).
Owner-occupancy
Not required
You don't have to live on-site — Colorado's HB24-1152 bars owner-occupancy mandates for subject jurisdictions.
Off-street parking
None required
No ADU off-street parking minimum by default. Louisville requires one off-street space for an ADU ONLY where on-street parking is prohibited on the subject block AND there are no excess parking spaces available on the lot (the City's expression of HB24-1152's narrow parking exception). City of Louisville ADU regulations.
Setbacks
Your zone's accessory setbacks
A detached ADU follows this city's accessory-structure setbacks, which vary by zoning district. Trace your lot in the planner and we'll show the exact side, rear, and front lines on your parcel.
Source
City of Louisville ADU regulations (LMC Title 17, Ch. 17.16; ADU ordinance adopted May 20, 2025, eff. June 23, 2025) — ADUs permitted in all zone districts (incl. PUDs) that allow single-family detached or attached dwellings; City of Louisville ADU requirements page (louisvilleco.gov). Colorado HB24-1152 (eff. June 30, 2025).
This is a plain-language summary for planning, not a legal determination. Codes are amended; confirm the current requirements with Louisville and a design professional before you rely on them.
A subject jurisdiction must allow at least one ADU by right (administrative — no discretionary review or public hearing) on any lot where a single-unit detached dwelling is an allowed use, and may not impose owner-occupancy mandates, ADU-specific minimum lot size, parking minimums (narrow exceptions only), or design standards stricter than the primary dwelling. It took effect June 30, 2025. That is why cities like Louisville now approve a backyard home administratively — and why owner-occupancy and parking mandates are largely gone.
We keep cited ADU rules for every city below. Switch to yours.
Draw your lot and house on the satellite map, drop an ADU, and see the setbacks and a budget range on your own property — in about a minute.
Keep exploring
ADU rules by city
Cited, city-by-city ADU rules across the Front Range.
Rental income potential
Real numbers on what ADUs earn.
ADUs for family
Aging parents, multigenerational living, childcare.
How to finance an ADU
HELOC, construction loans, and CHFA options.
Process & timeline
What to expect from contract to move-in.
Floor plans & pricing
Three sizes, three tiers, two styles.
About Addwell
Who we are and how we build.