ADU builders in Littleton, CO
Our shop, our crews, and most of our projects are all in town.
ADU rules in Littleton — Ordinance 09, Series 2025
Littleton rewrote its ADU rules recently and specifically, which makes this one of the clearer cities in the metro to build in. In response to HB24-1152, the city passed Ordinance No. 09, Series 2025, amending the Unified Land Use Code to permit accessory dwelling units in all residential zones — not a subset, all of them. The Planning Commission recommended it unanimously before council took it up.
The ordinance did more than open the map. It raised the maximum ADU size from 750 to 1,000 square feet, and allows ADUs to build to the height allowance of the zone district. The size cap works as the lesser of 1,000 square feet or roughly half the primary home’s living area — so on a modest downtown bungalow the practical ceiling is smaller than on a larger south-Littleton house. That’s the first number we check against your specific property.
An ADU is a complete home — foundation, utilities, permits, inspections. The rules decide what’s buildable before design starts, which is why we check them first.
Building an ADU on a Littleton lot
The two halves of Littleton produce two different ADU projects. Around Historic Downtown and Ketring, lots are older and often deeper than they look, and the classic build is a detached carriage house off the alley or a garage conversion — with the caveat that these homes frequently have dated electrical service that needs upgrading before it can carry a second dwelling.
South toward Southbridge and the Columbine-area subdivisions, the lots are larger and newer, the utilities are more modern, and the detached backyard ADU pencils more straightforwardly. The 1,000-square-foot ceiling goes further on these homes because the primary dwelling is bigger, so the 50% rule rarely binds first.
Permitting your Littleton ADU
Every ADU is permitted and inspected like a new home. In Littleton that runs through the City of Littleton’s Building Division at the Littleton Center on West Berry Avenue, via Littleton’s eTRAKiT portal. Under HB24-1152 the approval is administrative — no public hearing — but a detached unit still goes through full plan review, and utility connections, site work, and any required engineering are part of the scope. Any excavation also requires utility locates through Colorado 811. We handle the full path and give you a realistic timeline. Colorado has also been standing up a state ADU financing program through CHFA, and jurisdictions certified by DOLA as ADU Supportive make their residents eligible for additional funding — worth checking current status when you plan your budget. See our Denver ADU regulations guide for the wider legal picture.
We build ADUs throughout Littleton. Planning more than an ADU? We also handle basement finishing in Littleton and kitchen remodeling in Littleton, and everything we do locally is on our Littleton remodeling page.
ADU FAQs — Littleton
Since Ordinance No. 09, Series 2025, ADUs are permitted in all of Littleton’s residential zones. The remaining question is dimensional — what your specific lot and primary home allow — which we verify before design.
Up to 1,000 square feet, raised from the old 750-square-foot cap — but generally no more than about half your primary home’s living area, whichever is less. On smaller downtown homes that second limit is usually what binds.
Littleton spans Arapahoe, Jefferson, and Douglas counties, and some “Littleton” addresses sit outside the city entirely. We confirm jurisdiction before filing — for an ADU, that determines which ADU rules even apply.
Let’s build something right here in Littleton.
Send a note about your project, your timeline, and your budget — we’ll set up a free in-home walkthrough, usually within a few days. You’re a neighbor, not a lead.