ADUs in Douglas County, Colorado
Stone Aspen designs and builds custom accessory dwelling units, guest houses and detached living spaces throughout Douglas County, Colorado.
What is an ADU?
Accessory dwelling units — commonly called ADUs, guest houses, guest cottages, casitas, in-law suites or additional dwelling units — can create independent living space while making better use of the property you already own.
Throughout Douglas County, particularly on larger properties in Franktown, Sedalia, Parker, Larkspur, and surrounding areas, an ADU can provide space for aging parents, adult children, extended family or guests while maintaining privacy and connection to the main home.
But before designing the building, it is important to understand what the property can support.
At Stone Aspen, we begin there.
Can You Build an ADU on Your Douglas County Property?
The answer depends on more than the amount of available land.
Jurisdiction, zoning, lot size, setbacks, water and wastewater service, access, fire requirements, existing improvements and private covenants or HOA restrictions can all affect what may be possible.
In 2025, Douglas County expanded opportunities for accessory dwelling units, allowing both attached and detached ADUs across several single-family residential zoning districts, including Suburban Residential (SR), Estate Residential (ER), Rural Residential (RR), Large Rural Residential (LRR), and Agricultural (A-1).
For detached ADUs, minimum lot size can depend in part on the property's water source and applicable zoning district. In several Douglas County residential districts, current regulations establish a one-acre minimum for properties served by central water and a two-acre minimum for properties served by an individual groundwater well..
That makes early feasibility especially important.
An initial feasibility review may include jurisdiction, zoning, lot size, setbacks, water and wastewater service, existing improvements, access and other property-specific conditions that could influence the project.
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On a Well? The 35-Acre Distinction Matters
On acreage properties served by an exempt domestic well, ADU feasibility depends on more than zoning — it depends on what the well permit allows.
Colorado exempt well permits typically limit the number of homes a well can serve. Parcels of 35+ acres can often be permitted for up to three single-family dwellings; under 35 acres, serving a second dwelling usually requires additional water rights or an approved augmentation plan.
One exception: under DWR Guideline 2016-1, a detached space with its own entrance can count as an extension of the main home — not a second dwelling — if it avoids kitchen facilities: no stove, oven, or 240V cooking hookup, and no refrigerator over 6 cubic feet. A wet bar with a smaller fridge is fine.
Well permit type, acreage, and intended use all shape what we can design. If your property is on a well, talk with us early — we'll help you ask the right questions before you invest in design.
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ADUs in Franktown and Sedalia
Properties throughout Franktown and Sedalia often offer something increasingly difficult to find closer to Denver — room.
Larger lots and acreage properties can create opportunities for thoughtfully placed detached ADUs and guest houses while allowing the new structure to relate naturally to the existing home and surrounding landscape.
These properties can also introduce additional considerations.
Wells, septic systems, topography, drainage, driveway access, utilities and fire requirements can all influence where an ADU can be located and how it should be designed.
Rather than beginning with a predetermined building, we believe the better approach is to begin with the property.
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Have a Parker Address? Start With the Jurisdiction.
A Parker mailing address does not necessarily mean a property is located within the Town of Parker.
Many larger properties with Parker addresses are actually located in unincorporated Douglas County and may be governed by Douglas County zoning and development requirements rather than Town of Parker regulations.
That distinction can directly affect whether an ADU is permitted and what requirements apply.
Before discussing floor plans or architecture, we first want to answer a simpler question:
Who has jurisdiction over the property?
Once that is established, zoning, setbacks, utilities, access and other site-specific requirements can be evaluated under the appropriate regulations.
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ADUs in Larkspur
Larkspur's wooded setting, rolling terrain and foothill character can create beautiful opportunities for detached living spaces — along with site conditions that deserve careful consideration.
Properties within the incorporated Town of Larkspur and properties with a Larkspur mailing address outside Town limits may be governed by different requirements.
That distinction matters.
Zoning, topography, wildfire considerations, driveway and emergency access, water and wastewater systems, utilities and existing improvements may all influence what can be built and where it can be located.
The first step is confirming the property's jurisdiction and understanding the requirements that apply before beginning design.
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What Is the Difference Between an ADU and a Guest House?
The terminology can be confusing because homeowners, builders and jurisdictions do not always use the same words in the same way.
An Accessory Dwelling Unit (ADU) generally refers to a secondary living space associated with a primary residence. A true dwelling unit typically includes the facilities necessary for independent living, such as sleeping, bathing and cooking.
A guest house or guest cottage may look very similar architecturally but can be treated differently depending on its features and the regulations governing the property.
That is why the name of the building matters less at the beginning than understanding how you intend to use the space.
Tell us what you want the building to do. We can then help determine how that use relates to the property and the requirements that may apply.
Guest House · Guest Cottage · Casita · In-Law Suite · Mother-in-Law Suite · Backyard Cottage · Carriage House · Detached ADU
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ADUs for Aging Parents
For many families, an ADU is not primarily about adding square footage. It is about creating the right amount of independence and connection.
A detached living space can allow an aging parent to remain close to family while maintaining a home of their own.
When the intended resident is an aging parent, we can also consider the home differently from the beginning — including single-level living, accessible entries, wider circulation, bathroom layout, lighting and other details that may make the space easier to live in over time.
The goal is a home that feels comfortable and independent today while anticipating what may be helpful tomorrow.
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Independent Space for Adult Children
An ADU can also provide adult children with something increasingly difficult to achieve: independence while remaining close to home.
A thoughtfully designed detached space can provide privacy for work, study and everyday living while preserving a connection to the family and property. And because the building becomes part of the property rather than serving only one moment in a family's life, its purpose can evolve over time — from space for an adult child to accommodations for guests, extended family or future needs.
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Wells, Septic & Utilities
On many Douglas County acreage properties, the building itself is only one part of the feasibility question.
The existing infrastructure serving the property can have a significant influence on an ADU project.
Depending on the site, we may need to understand the existing water source, well capacity, wastewater and septic system, electrical service, gas or propane availability, heating and cooling options, drainage, grading, driveway configuration and emergency access.
These aren't details to address after the design is complete.
They are part of determining what should be designed in the first place.
WATER SUPPLY · WELL CAPACITY · WASTEWATER & SEPTIC · ELECTRICAL SERVICE · GAS OR PROPANE · HEATING & COOLING · DRAINAGE & GRADING · DRIVEWAY & EMERGENCY ACCESS
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Designed for the Property
Every property has its own architecture, views, terrain and opportunities.
A detached structure should respond to those conditions rather than feel like a building that could have been placed anywhere.
We consider the relationship between the ADU and the primary residence, including architecture, materials, scale, orientation, privacy, outdoor space, access and views.
Sometimes the right solution closely reflects the architecture of the existing home. Other times, a simpler complementary structure creates a better relationship.
Our goal is not simply to find a place where another building fits. It is to create a space that feels like it belongs.
The result should enhance the property while serving the people who will use it.
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Start With Feasibility
If you're considering an ADU, guest house or detached living space in Douglas County, you don't need to begin with a finished design.
Begin with the property and what you hope to accomplish.
Stone Aspen can help evaluate the initial feasibility, identify the questions that need to be answered and determine the appropriate next steps before significant time and money are invested in design.
From there, we can work with you to develop a detached living space thoughtfully designed for your property, your family and the way you intend to use it.
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LET’S START A CONVERSATION
Tell Us Your Story.
Whether you're building a custom home, exploring detached living spaces, or wondering what's possible for your property, we'd love to hear your story.