Accessory Structures in Castle Rock, CO: What Residents Actually Need to Know
If you live in Castle Rock or are thinking about moving there, accessory structures are one of those things you probably won't think about until they affect you directly. Castle Rock has 5 specific rules on the books covering different aspects of accessory structures, and some of them might surprise you.
Garage Conversions
Converting a garage into finished living space or an ADU requires a building permit in Castle Rock, submitted through the eTRAKiT Development Portal. If the converted space becomes a separate dwelling unit, it must comply with the Chapter 17.61 ADU rules, including the one-per-lot limit and recorded deed restriction.
Key details: Permit: Required (eTRAKiT). If separate unit: Treated as ADU (Ch. 17.61). ADUs per lot: One maximum. Building code: Adopted IRC, Title 15. Deed restriction: Required for ADU.
Converting a garage into living space without permits, or creating an unpermitted second dwelling, is a code violation subject to Town enforcement and orders to correct or restore.
ADU Rules
Castle Rock allows accessory dwelling units, but no more than one ADU per lot. Before a building permit issues, the owner must record a deed restriction barring rental of both the primary home and the ADU at the same time, and no separate water/sewer taps are permitted.
Key details: ADUs per lot: One maximum. Governing code: Chapter 17.61. Deed restriction: Required before permit. Separate utility taps: Not allowed. Separate sale: Prohibited.
Building without a permit or without the required recorded deed restriction is a zoning-code violation subject to Town Code Compliance enforcement, stop-work, and correction orders.
Shed Rules
Sheds and other detached accessory buildings are governed by Castle Rock's Zoning Code (Title 17). Accessory buildings must sit behind the primary home in the rear yard, meet reduced side/rear setbacks, and are capped at a lower height than the main house. Larger sheds also need a building permit.
Key details: Governing code: Zoning Title 17. R-1 accessory height: About 20 feet. Location: Rear yard. Building permit: Size-dependent (Title 15). Confirm permits: 720-733-3527.
A shed placed in a required setback, over the height limit, or built without a required permit is a violation subject to correction orders and possible removal.
Tiny Homes
Castle Rock has no dedicated tiny-home ordinance. A tiny house on a permanent foundation must meet the adopted International Residential Code (Title 15) and zoning district standards. A tiny house built as a second unit is regulated as an ADU under Chapter 17.61. Tiny houses on wheels (RVs) cannot be
Key details: Dedicated tiny-home code: None. Foundation tiny home: Meets IRC + zoning. As second unit: Regulated as ADU. Tiny home on wheels: Treated as RV. Permanent RV living: Not allowed.
Living in a tiny house on wheels as a permanent residence, or building a foundation tiny home without permits, is a code violation subject to enforcement.
Carport Rules
A carport is an accessory structure and is regulated under Castle Rock's Zoning Code (Title 17) like other accessory buildings: it must respect required setbacks, meet the accessory-structure height limit, and typically requires a building permit. HOA covenants in many Castle Rock subdivisions add stricter design rules.
Key details: Classified as: Accessory structure. Governing code: Zoning Title 17. Building permit: Generally required. R-1 height cap: About 20 feet. HOA rules: Often stricter.
An unpermitted carport, or one intruding into a required setback, is a zoning/building violation subject to correction orders and potential removal.
The Bottom Line
Castle Rock's accessory structures rules are a mixed bag. Some areas are strict, others are relaxed, and the details matter. The best approach is to check the specific rule that applies to your situation rather than assuming Castle Rock is broadly strict or permissive.
Keep in mind that Castle Rock can amend these rules at any council meeting. For the most current version of any rule mentioned here, check the specific ordinance page, where we track updates as they happen.