Accessory Dwelling Unit (ADU) Regulations in Castle Rock

Max Size- 

• Attached & Detached: 800 sq/ft or 50% of primary structure (whichever is less)
• Interior: 50% of primary structure

Max Height- Cannot exceed height of primary structure

To qualify for an ADU in Castle Rock, your property must meet the following conditions:

• Only one ADU is permitted per lot.
• The ADU must be accessory to a single-family home.
• ADUs are not allowed on properties with duplexes, townhomes, condos, or multifamily units.
• Mobile homes, RVs, and temporary structures cannot be used as ADUs.

In some cases, homeowners must obtain a Use By Special Review (UBSR) approval before building an ADU. However, UBSR is not required if:

• The ADU is built within an existing structure with no additional square footage added.
• The ADU is included in the original building permit for a new single-family home.

Castle Rock has specific size limitations and design standards for ADUs to ensure they blend well within neighborhoods:

• Maximum ADU Size:
  
  • Interior ADUs cannot exceed 50% of the primary home’s total floor area.
  • Detached ADUs and additions cannot exceed 800 sq/ft, unless the property is in a zoning district with different size limits.
• Architectural Compatibility: The ADU must match the design, materials, and character of the primary home.
• Foundation Requirements: ADUs must be permanently affixed to an engineered foundation.
• Setbacks: ADUs must meet all setback requirements for the zoning district.

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• HB 24-1152 requires cities to allow ADUs without designated parking, except in these cases:
  ✔ If no parking is currently required for the primary home, parking cannot be required for the ADU.
  ✔ If the lot does not have an existing parking space for the primary home, no additional parking is required.

• Entrances must be positioned to maintain privacy and new ADU entrances visible from the street must be limited.
• Driveways must meet Castle Rock’s building and zoning standards.

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• ADUs must share water and sewer connections with the primary home separate taps are not permitted, which saves the homeowner money.
• All utility bills will be charged to the primary residence’s account holder.
• If an ADU requires a larger water tap size, the homeowner must pay the incremental System Development Fees.

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• HB 24-1152 prohibits cities from requiring owner occupancy meaning ADUs can be rented out separately from the primary home.
• ADUs cannot be sold separately from the main home—they must remain part of the same lot.
• Short-term rentals (STRs) are still prohibited, except in Planned Unit Developments (PUDs) where STRs were previously allowed.

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Under HB 24-1152, all ADU approvals must be handled administratively—meaning there are:
✔ No public hearings
✔ No subjective design reviews
✔ No neighborhood approval required

Homeowners must obtain a building permit before constructing an ADU. The permit process includes:

1. Submitting a General Permit Application to the Building Department.
2. Providing site plans, floor plans, and architectural drawings.
3. Recording a deed restriction stating that the ADU cannot be sold separately from the main home and that only one unit can be rented at a time.

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Building an ADU in Castle Rock requires careful planning, compliance with zoning laws, and expert execution; that's where Kindred Tiny Homes comes in.

• We handle everything from design and permitting to construction and final approvals.
• We navigate Castle Rock’s ADU requirements seamlessly, ensuring your project is fully compliant and stress-free.
• We create high-quality, beautifully designed ADUs that enhance property value and maximize functionality.

If you’re considering building an ADU in Castle Rock, contact us today for a free consultation, we’ll walk you through your options and help bring your vision to life!

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