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 ADU finder reads them off your parcel.
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). ★ TWO AREAS DO NOT COUNT toward these maxima: an ATTACHED ADU in a basement that is partially or fully below grade is excluded entirely (§17.16.035(B)(3)(d)), and GARAGE areas are excluded from the calculation (§(B)(3)(e)). ★ Landmark (ch. 15.36), deed-restricted-affordable (ch. 17.76), or accessible ADUs may take ONE size increase — to 1,000 sf detached / 1,200 sf attached (§(E)). LMC §17.16.035(B)(3)–(4); 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. Enter your address in the ADU finder and we'll pull your parcel and show the exact side, rear, and front lines on it.
Source
Louisville Municipal Code §17.16.035 (Accessory dwelling units), with the definitions at §§17.08.011–.013, added by Ord. No. 1892-2025 §§1 and 4, 3-18-2025 — read from Municode 2026-08-27. ADUs are permitted in all zone districts (including PUDs) that allow single-family detached or attached dwellings. ⓘ The City's own ADU requirements page (louisvilleco.gov) describes the same rules and dates the ordinance adopted 20 May 2025, effective 23 June 2025; Municode stamps the codified section 3-18-2025. Both are given because they disagree and we have not established which action each describes. Colorado HB24-1152 (eff. 30 June 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.
Enter your address and we pull your parcel lines and your district’s ADU setbacks. Trace your house, place one of our plans, and see what fits and what it would cost — in a few minutes.
Keep exploring
ADU rules by city
Cited, city-by-city ADU rules across the Front Range.
Questions answered
Allowed, how big, what it costs, how long — answered from the adopted codes.
How the finder works
What to type, what you get back, and what it deliberately will not tell you.
Rental income potential
Rent, resale value, and what a permitted second unit adds to your property.
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
Five plans, three finish grades, five architectural styles.
About Addwell
Who we are and how we build.