Colorado ADU law now gives many homeowners stronger rights to build an accessory dwelling unit under HB24-1152. In subject jurisdictions, qualifying properties must generally be allowed one ADU where a single-unit detached home is permitted.
The law also limits certain local barriers, including continuing owner-occupancy requirements, automatic parking mandates, restrictive lot-size rules, and some setback and design restrictions.
Local rules still matter. Building codes, utilities, permits, historic requirements, short-term rental rules, and property-specific conditions can still determine whether an ADU can actually be built.
This guide explains where HB24-1152 applies, which properties may qualify, what local governments can still regulate, and what homeowners should check before starting an ADU project.
Key Takeaways
- HB24-1152 created statewide ADU protections in qualifying Colorado jurisdictions. Beginning June 30, 2025, subject jurisdictions must allow one qualifying ADU as an accessory use to a single-unit detached dwelling wherever those homes are permitted.
- Colorado ADU law does not make every property automatically eligible. The location of the parcel, zoning, water and sewer access, hazards, easements, and other property conditions can still affect whether an ADU can be constructed.
- Qualifying ADUs use an administrative approval process. Applications generally must be evaluated using objective standards instead of requiring a discretionary public hearing simply because an ADU is proposed.
- Internal, attached, and detached ADUs are protected forms of accessory housing. A local definition cannot be written in a way that effectively excludes these basic ADU configurations from the statewide framework.
- Owner occupancy and parking are less restrictive under the state law. Subject jurisdictions generally cannot require continuing owner occupancy or construction of a new off-street parking space solely because an ADU is being created, although specific exceptions remain.
- Building and safety requirements still apply. An ADU may still need zoning approval, construction permits, building-code compliance, fire-code compliance, utility approval, inspections, and a certificate of occupancy.
- Local rules still matter. Colorado establishes the baseline, but homeowners must check the current ADU ordinance and development standards for the city or county where the property is located.
What Is the Colorado ADU Law and What Did HB24-1152 Change?
HB24-1152, titled the Accessory Dwelling Units bill, created Colorado’s primary statewide framework for expanding ADU availability. The legislation was adopted in 2024 as part of the state’s effort to increase housing options within communities that already allow detached residential homes.
The law focuses on adding housing within established residential areas rather than relying entirely on large new developments. ADUs can add smaller homes to existing lots through basement conversions, additions, garage conversions, backyard cottages, and similar projects.
For homeowners, one of the most significant changes is that ADU eligibility in covered jurisdictions is no longer entirely dependent on whether a local government chooses to permit the use. A subject jurisdiction must allow one ADU as an accessory use to a single-unit detached dwelling in areas where that type of primary dwelling is permitted.
This requirement applies through an administrative approval process. If an application meets the objective standards established by law and the applicable local code, the approval process should not depend on subjective opinions about whether the neighborhood needs another dwelling.
How the Statewide Framework Changed ADU Regulation
Before the statewide reform, the feasibility of building an ADU could differ dramatically between nearby Colorado communities. One city might permit detached backyard units, while another could restrict them through lot-size thresholds, parking requirements, owner-occupancy conditions, or discretionary approvals.
HB24-1152 establishes a minimum level of ADU access in subject jurisdictions.
| ADU Issue | Statewide HB24-1152 Framework |
| ADU availability | One ADU must generally be allowed with a single-unit detached dwelling in covered areas |
| Approval process | Administrative approval based on objective standards |
| Owner occupancy | Continuing owner occupancy generally cannot be required |
| New parking | New off-street parking generally cannot be required solely for the ADU |
| ADU configuration | Internal, attached, and detached forms cannot be categorically excluded through the ADU definition |
| Design and dimensional rules | Restrictive standards prohibited by the statute cannot be imposed |
| Local building regulations | Building, fire, utility, and other lawful regulations may still apply |
The change is significant, but it is not complete state control of local land use.
Colorado did not create a single statewide ADU building code that tells every homeowner exactly how large a unit can be, how high it can be, where every wall must sit, or how utility service must be installed. Many of those details remain within local government authority as long as the rules do not conflict with the statewide protections.
Why Colorado Expanded ADU Rights
ADUs can add housing without requiring an existing neighborhood to be completely redeveloped. A single residential lot can potentially accommodate another household while retaining the primary home.
That additional unit might be used by an adult child, an aging parent, a caregiver, a long-term tenant, or the homeowner after moving into the smaller residence.
ADUs can therefore contribute to several housing goals at once. They can support infill housing, increase residential density gradually, create smaller rental units, and allow families to use existing land more efficiently.
They are not automatically affordable housing, and construction costs can still be substantial. However, allowing more homeowners to create ADUs increases the range of housing types available in communities dominated by detached homes.
HB24-1152 Did Not Eliminate Local ADU Ordinances
One of the easiest mistakes to make is assuming that HB24-1152 replaced local zoning.
It did not.
Cities and counties continue to adopt and enforce ADU ordinances, zoning codes, building regulations, and permitting procedures. The difference is that a subject jurisdiction’s local rules must now operate within the limits established by Colorado law.
A local government can still determine whether plans comply with legitimate objective requirements. It can enforce building and fire codes, review utility connections, regulate structures within historic districts, administer inspections, and address site-specific hazards.
What it generally cannot do is use prohibited restrictions to make the ADU right meaningless.
For a homeowner, the practical question is therefore not simply, “Are ADUs legal in Colorado?”
The better question is, “What rights does Colorado law give me on this particular parcel, and what lawful local requirements must my project still meet?”
Where Does Colorado ADU Law Apply? Understanding Subject Jurisdictions
HB24-1152 uses the term subject jurisdiction to identify the local governments required to follow its mandatory ADU provisions.
This distinction matters because not every municipality, county, or rural property in Colorado is regulated in exactly the same way.
Under the enacted law, a subject jurisdiction includes a municipality with a population of at least 1,000 that is located within a metropolitan planning organization. It can also include certain portions of counties that meet the population, census-designated place, and metropolitan planning organization requirements established by the statute.
The county provision is especially important. The fact that part of a county is subject to the law does not necessarily mean every parcel within that county receives the same statewide protection.
What Is a Metropolitan Planning Organization?
A metropolitan planning organization, commonly abbreviated as MPO, is an organization responsible for transportation planning within qualifying urbanized areas.
HB24-1152 uses location within an MPO as one of the factors for determining which municipalities and county areas fall within the mandatory statewide ADU framework.
For the average homeowner, there is usually no need to research transportation planning boundaries from scratch before making an initial inquiry. The local planning department should be able to identify whether the property is within a jurisdiction subject to HB24-1152.
Still, the distinction helps explain why statewide ADU rules may apply differently to two properties located in different parts of Colorado.
Subject Jurisdiction Does Not Mean Every Parcel Is Buildable
Even within a subject jurisdiction, property-specific limitations can matter.
For example, Colorado’s Department of Local Affairs notes that certain parcels may qualify for exceptions, including properties in floodplains and parcels without access to domestic water and sewer systems.
A property could also have physical constraints that affect actual construction. Utility easements, access easements, steep terrain, existing structures, drainage facilities, or limited buildable area can influence whether a detached unit fits on the site.
The statewide rule establishes a land-use right. It does not guarantee that every possible ADU design will satisfy building, utility, environmental, or site requirements.
State Law Sets the Minimum, but Local Codes Still Fill in the Details
For the ADU restrictions specifically covered by HB24-1152, a subject jurisdiction cannot enforce a conflicting local rule in a way that defeats the statewide requirement. Beginning June 30, 2025, subject jurisdictions are prohibited from enacting or enforcing the types of local restrictions that the statute expressly prohibits.
This distinction matters when a homeowner finds older zoning language, an outdated municipal webpage, or permit guidance that appears more restrictive than current Colorado law. The existence of an older local rule does not necessarily mean that rule can still be enforced against a qualifying ADU if it conflicts with HB24-1152.
At the same time, state law does not replace the entire local ADU ordinance. Cities and counties still control many requirements that HB24-1152 leaves within local authority, including building and fire codes, utilities, stormwater requirements, historic district procedures, short-term rental rules, generally applicable impact fees, and other lawful development standards.
Homeowners who encounter conflicting information should check the date of the local guidance and confirm the current ordinance or interpretation with the planning department rather than assuming an older municipal webpage overrides the newer state requirements.
Jurisdiction Boundaries Matter
Homeowners should determine whether the property is inside an incorporated city or town or located in an unincorporated portion of a county.
A mailing address alone may not answer that question.
For example, a property can use the name of a nearby city in its mailing address while technically sitting outside municipal boundaries. In that situation, county ADU rules rather than city zoning may control the application.
This becomes particularly important when searching online for requirements. Reading a city’s ADU webpage does not help if the property is actually governed by the county.
A planning department can typically confirm the governing jurisdiction using the parcel number or property address.
What About Jurisdictions That Are Not Subject to HB24-1152?
A local government that does not fall within the mandatory definition can still choose to support ADU development.
Colorado created the concept of an ADU supportive jurisdiction, allowing participating local governments to demonstrate compliance with state ADU standards and implement strategies designed to encourage accessory dwelling unit construction.
The state framework also created grant and financing initiatives connected with ADU-supportive policies.
This means homeowners outside a mandatory subject jurisdiction should not assume that ADUs are prohibited. A city or county may independently permit them under its own local ordinance or may voluntarily follow standards similar to those required by HB24-1152.
How to Check Whether Your City or County Is Covered
The legal definition of a subject jurisdiction is useful, but most homeowners have a simpler question: Does HB24-1152 apply to my property?
Colorado’s Department of Local Affairs provides a Multilaw Applicability Web App that helps answer that question. The tool allows users to select a jurisdiction, search for a specific address, and filter by individual state land-use laws to see which requirements apply in that community.
For a homeowner researching Colorado ADU law, this is a useful first check before interpreting a city or county ordinance.
Start by identifying whether the property is inside an incorporated municipality or an unincorporated county area. Then use the state applicability tool or current local planning information to determine whether HB24-1152 applies.
After confirming the jurisdiction, check whether single-unit detached dwellings are allowed on the parcel and whether the property is subject to an exemption or another site-specific limitation.
| Question to Check | Why It Matters |
| Is the property inside a city or an unincorporated county area? | Determines which local government regulates the parcel |
| Does HB24-1152 apply to that jurisdiction or area? | Determines whether the statewide ADU protections apply |
| Is a single-unit detached dwelling allowed on the parcel? | The state ADU requirement is tied to areas allowing this housing type |
| Is the parcel exempt from the statewide requirement? | Certain properties can fall outside the mandatory ADU allowance |
| Does the property have adequate water and sewer service? | Utility limitations can affect eligibility and permitting |
| Are there easements, flood hazards, or other site constraints? | A qualifying parcel can still face physical development limitations |
The Department of Local Affairs applicability tool is especially helpful because county coverage can be more complicated than municipal coverage. HB24-1152 does not automatically apply to every unincorporated parcel simply because part of a county falls within the state framework.
Homeowners should still verify the result against the current planning or zoning information for the property before spending money on architectural plans. The state tool can establish whether the statewide legislation applies, while the city or county code provides the detailed standards that govern the actual project.
For properties near municipal boundaries, confirming jurisdiction is particularly important. A mailing address may use the name of a nearby city even when the parcel is legally located in an unincorporated county area.
The safest sequence is address → jurisdiction → HB24-1152 applicability → zoning → parcel conditions. Once those questions are answered, the homeowner can move on to ADU size, setbacks, utilities, design, and permitting.
What Does “Use by Right” and Administrative Approval Mean for an ADU?
The phrase use by right is important when discussing Colorado ADU law because it changes how an eligible ADU is treated by the zoning process.
In practical terms, an eligible ADU should not need special political or discretionary approval simply because it is an ADU.
HB24-1152 requires subject jurisdictions to allow one accessory dwelling unit through an administrative approval process as an accessory use to a single-unit detached dwelling in areas where those dwellings are allowed.
This does not mean automatic approval without an application.
It means the decision is generally based on whether the proposed unit satisfies objective requirements.
Administrative Approval Versus Discretionary Approval
An administrative approval is typically handled by planning or permitting staff. The reviewer compares the application against requirements written into the zoning or development code.
A discretionary process works differently. A planning commission, board, elected body, or other decision-maker may have greater authority to decide whether a proposed use is appropriate in a particular location.
| Administrative Approval | Discretionary Approval |
| Based on objective code requirements | May include subjective considerations |
| Commonly reviewed by staff | May involve a board or commission |
| Approval follows compliance with applicable standards | Approval may depend on additional findings |
| Public hearing generally not required simply for the use | Public hearing may be part of the process |
| More predictable for applicants | Outcome can be less predictable |
The administrative model does not prevent public involvement in broader zoning decisions. Communities can still debate and adopt development standards through normal legislative processes.
What changes is the treatment of an individual qualifying ADU application after those objective rules are established.
What Are Objective Standards?
Objective standards are requirements that can be applied without relying primarily on personal judgment.
A maximum building height is an objective standard because a reviewer can measure the proposed height. A defined setback is objective because the distance between a structure and property line can be shown on a site plan.
Building-code provisions are another example. A wall assembly either satisfies the applicable construction requirement or it does not.
A rule stating that an ADU must “fit the character of the neighborhood,” without measurable criteria, creates more room for subjective judgment.
HB24-1152’s administrative approval framework is intended to give property owners a more predictable process when they meet applicable requirements.
Can an Administrative ADU Application Still Be Denied?
Yes.
Use by right does not mean a homeowner is entitled to build any ADU design on any portion of the property.
An application can still fail if it does not comply with lawful standards involving setbacks, building height, lot coverage, construction safety, utilities, access, or other applicable requirements.
The difference is the basis for the decision.
If the proposed ADU meets the objective standards governing the property, a subject jurisdiction generally cannot require the homeowner to prove that the neighborhood personally needs or wants the unit.
Does Administrative Approval Eliminate Permits?
No.
Zoning entitlement and construction approval are related but separate parts of the project.
A homeowner may have a right to construct an ADU under the land-use code but still need a building permit before construction begins. Electrical, plumbing, mechanical, fire, sewer, or other approvals may also be required depending on the design.
Inspections take place as work progresses, and the completed unit may need final approval or a certificate of occupancy before legal residential use begins.
Use by right therefore makes the land-use process more predictable. It does not remove the responsibility to build a safe, code-compliant dwelling.
Which Properties and Types of ADUs Can Qualify?
Colorado ADU law protects more than one physical type of accessory dwelling unit.
A local government cannot define an ADU so narrowly that the definition excludes internal, attached, or detached configurations from the statewide framework. Colorado’s Department of Local Affairs specifically identifies these three forms in its summary of HB24-1152.
For homeowners, this creates flexibility because adding housing does not always require constructing an entirely new backyard building.
Internal ADU
An internal ADU is created inside an existing or proposed primary home.
A basement conversion is one of the most common examples. Depending on the floor plan, homeowners may also be able to convert another portion of the house into an independent dwelling.
The space still needs to function as a legal dwelling unit. Building-code requirements involving ceiling height, emergency escape, fire separation, electrical systems, plumbing, ventilation, and other safety issues may affect whether an existing area can be converted.
An unfinished basement that appears large enough for an apartment is therefore not automatically a legal ADU.
Internal conversions can be attractive because the primary building envelope already exists. They may also avoid some site-planning challenges associated with placing a second structure in the yard.
Attached ADU
An attached ADU is physically connected to the primary residence.
This could include a side or rear addition designed as an independent dwelling or another attached configuration permitted by local building and zoning rules.
An attached unit can be useful when the existing home lacks enough interior area for a conversion but the property has room to expand.
The addition must still comply with applicable lot coverage, setbacks, building height, structural, utility, and construction requirements.
Detached ADU
A detached ADU is a separate residential structure on the same lot as the primary home.
It is often described as a backyard cottage, carriage house, granny flat, or detached accessory dwelling.
Detached units provide greater physical separation between households, which can be useful for long-term tenants, extended family, or homeowners seeking more privacy.
They also tend to involve more site planning than an internal conversion. The project may require a foundation, utility extensions, drainage planning, structural construction, and careful placement around setbacks and easements.
Garage Conversion
A garage conversion can create an ADU by converting part or all of an existing accessory structure into living space.
Some projects convert an attached garage. Others create a dwelling within or above a detached garage.
A garage’s existing shell can make conversion appear straightforward, but garages were not necessarily constructed to residential standards.
Insulation, foundations, floor systems, fire separation, windows, emergency exits, plumbing, heating, electrical service, and ceiling height may all need review before the space qualifies as habitable housing.
The existence of an old garage also does not guarantee that the building can legally become an ADU. A structure may be legal in its current location while a change to residential occupancy triggers additional code requirements.
How the Main ADU Types Compare
| ADU Type | Typical Example | Main Planning Considerations |
| Internal ADU | Basement apartment | Egress, fire separation, ceiling height, utilities |
| Attached ADU | Addition to the main house | Setbacks, lot coverage, structural connection |
| Detached ADU | Backyard cottage | Building area, utilities, setbacks, height |
| Garage conversion | Apartment in or above a garage | Existing structure, fire safety, habitability, utilities |
What Makes a Property Potentially Eligible?
The statewide protection centers on property where a single-unit detached dwelling is allowed.
That does not mean the property must be completely developed before an ADU can be considered. The law addresses ADUs as accessory uses to single-unit detached dwellings, and project configuration can vary depending on whether the primary residence already exists or is being developed at the same time.
The property’s zoning is only the beginning of the analysis.
A homeowner planning a detached ADU should also determine whether there is sufficient buildable area after accounting for the primary home, accessory structures, required setbacks, lot coverage, utility easements, access, drainage features, and other constraints.
An internal conversion may avoid some of those land constraints but create different building-code challenges.
Water and sewer availability can also determine feasibility. This becomes particularly important on properties served by septic systems, wells, limited utility infrastructure, or other nonstandard service arrangements.
Historic properties may face additional review, while properties in flood-prone areas can be subject to special restrictions.
For that reason, homeowners should choose the type of ADU only after understanding the property itself.
The most practical sequence is to confirm the governing jurisdiction, verify zoning, identify property constraints, evaluate utilities, and then determine whether an internal, attached, detached, or conversion project offers the best path forward.
Colorado ADU Size, Lot Size, Setback, Height, and Lot Coverage Rules
Colorado ADU law limits several dimensional rules that subject jurisdictions can use to regulate accessory dwelling units. These protections are intended to prevent local standards from technically allowing ADUs while making them impractical to build on ordinary residential lots.
The protections do not create one universal ADU design for every property. Local zoning codes can still regulate dimensions that are not prohibited by HB24-1152, so homeowners need to compare the statewide rules with the zoning district that applies to their parcel.
How Large Can an ADU Be in Colorado?
HB24-1152 treats a local standard as restrictive if it does not allow ADU sizes between 500 and 750 square feet. In other words, a subject jurisdiction must provide a workable path for an ADU within that protected size range.
That does not make 750 square feet a statewide maximum.
A local government may allow an ADU smaller than 500 square feet or larger than the state-protected range. The statute specifically preserves local authority to allow units smaller than 500 square feet or greater than 800 square feet. It also permits a jurisdiction to prevent an ADU from being larger than the principal dwelling on the same lot.
The result is an important distinction between a state-protected size range and a local maximum size.
| ADU Size Issue | Colorado State Framework | What to Check Locally |
| 500 to 750 sq. ft. | Must be accommodated in subject jurisdictions | Local dimensional standards still apply |
| Below 500 sq. ft. | May be allowed | Minimum size and building-code requirements |
| Above 750 sq. ft. | May be allowed | Local maximum floor area |
| Very large ADU | Not guaranteed by state law | Maximum size and relation to primary dwelling |
| ADU larger than primary home | May be restricted | Local floor-area rules |
A homeowner should therefore avoid assuming that every city has the same maximum ADU size. One jurisdiction might allow a 750-square-foot backyard cottage, while another may permit substantially more floor area under its local ordinance.
Minimum Lot Size Restrictions
HB24-1152 also limits how minimum lot-size requirements can be used against ADUs.
A subject jurisdiction cannot impose a more restrictive minimum lot size for an ADU than it applies to a single-unit detached dwelling within the same zoning district.
Suppose a zoning district permits a detached house on a 5,000-square-foot lot. A local government generally could not create a separate ADU rule requiring 8,000 square feet solely because the homeowner wants to add an accessory dwelling unit.
This protection is especially relevant in older neighborhoods where residential lots may be relatively small.
It does not mean every small lot can physically accommodate a detached ADU. Existing buildings, setbacks, easements, lot coverage, utilities, access, and drainage conditions may leave too little usable space for a new structure.
An internal or attached ADU may be more practical on a constrained parcel.
Side Setback Requirements
A setback establishes the minimum distance between a building and a property line or other defined feature.
Under HB24-1152, a local standard is considered restrictive if it requires an ADU to have a larger side setback than the side setback required for the primary dwelling in the same zoning district.
For example, if the primary home is subject to a five-foot side setback, the jurisdiction generally cannot impose a larger ADU-specific side setback that undermines the ability to place the unit on the lot.
A local government can still apply lawful setback requirements. The state rule limits unusually restrictive treatment of the ADU rather than eliminating setbacks completely.
Rear Setback Requirements
Colorado law provides a more specific framework for rear setbacks.
A local ADU standard is considered restrictive if the required rear setback exceeds the greater of the rear setback required for other accessory building types in the same zoning district or five feet.
This matters most for detached ADUs because backyard placement often depends on the usable depth of the parcel.
Consider a zoning district where detached garages and sheds have a three-foot rear setback. Under the state framework, the applicable ADU rule cannot become restrictive by demanding a much larger rear yard solely because the accessory structure contains housing.
Property owners should still confirm whether additional requirements apply because of alleys, utility easements, fire access, drainage, or other property-specific conditions.
Building Height
HB24-1152 does not establish one statewide maximum building height for every ADU.
Cities and counties can continue applying dimensional standards that do not meet the statute’s definition of a prohibited restrictive design or dimension standard. This means local regulations involving maximum structure height, number of stories, roof form, or similar measurable standards may still affect an ADU.
Height can be especially important for a detached ADU proposed above a garage.
A one-story backyard cottage may easily comply with a local accessory-building height limit, while a two-story carriage house may require closer review.
Do not assume that because the state protects detached ADUs, it also guarantees a two-story detached ADU.
Lot Coverage and Floor Area
Lot coverage measures how much of the property may be covered by buildings or other regulated improvements.
A local zoning district may establish a maximum percentage of the lot that can be occupied by the primary house, garage, ADU, and other structures.
This can become the practical limiting factor on otherwise eligible properties.
For example, a homeowner may have sufficient rear setback space for an ADU but already be near the maximum lot coverage because of the primary home, attached garage, covered patio, or other improvements.
Floor-area regulations may create similar constraints. Some jurisdictions calculate maximum building area using total floor area, building footprint, floor-area ratio, or another zoning measurement.
HB24-1152 restricts certain ADU-specific dimensional barriers, but it does not erase every generally applicable development standard.
The best approach is to analyze the parcel as a whole rather than focusing only on ADU square footage.
Parking, Owner-Occupancy, and ADU Design Standards
Parking requirements and owner-occupancy rules have historically been two of the most significant barriers to ADU development.
HB24-1152 substantially limits both in subject jurisdictions while also restricting design standards that treat ADUs more harshly than primary homes.
Owner-Occupancy Requirements
Beginning June 30, 2025, a subject jurisdiction generally cannot require either the ADU or another dwelling on the same lot to remain owner-occupied.
This is important for homeowners who eventually move, rent both dwellings, transfer the property, or use the homes differently over time.
Without this protection, an ADU permit could effectively depend on the original owner continuing to live on the parcel indefinitely.
Colorado law does preserve limited exceptions.
A subject jurisdiction may require a property owner to demonstrate residence on the parcel when applying to construct or convert an ADU. That exception does not apply when the ADU and a new primary dwelling are constructed simultaneously.
Owner occupancy may also be required in connection with a local short-term rental license or permit.
This distinction is important. A city may not be able to impose permanent owner occupancy simply because the property contains an ADU, while still being able to impose an owner-occupancy rule if the homeowner wants to operate a short-term rental.
Parking Requirements
HB24-1152 generally prohibits a subject jurisdiction from requiring construction of a new off-street parking space solely because an ADU is being constructed or converted.
That does not mean parking can never matter.
If the property already contains an available driveway, garage, tandem space, or other off-street space, a jurisdiction may require that an existing space be designated for the ADU.
There is also a narrow circumstance in which one new parking space may be required.
The parcel must lack an existing off-street parking space that could serve the ADU, the zoning district must have required parking for the primary dwelling as of January 1, 2024, and the property must be located on a block where on-street parking is prohibited. All of those conditions are part of the statutory exception.
| Parking Situation | General Treatment Under HB24-1152 |
| Existing driveway available | Existing space may be designated |
| Existing garage or tandem space available | Existing space may potentially satisfy the requirement |
| No existing off-street parking | New parking generally still cannot automatically be required |
| No parking plus qualifying zoning and no on-street parking | One new space may be required if statutory conditions are met |
| ADU created on typical lot with street parking | Automatic new parking mandate generally prohibited |
For many homeowners, this protection can preserve valuable yard area that would otherwise have to be paved for another parking space.
Design Standards
Colorado also limits architectural and aesthetic requirements that single out ADUs for more restrictive treatment.
A jurisdiction cannot impose a required architectural style, building material, or landscaping rule that is more restrictive for an ADU than for a single-unit detached dwelling in the same zoning district.
For example, a city could not ordinarily require an ADU to use unusually expensive exterior materials if the same requirement does not apply to the primary homes within that zoning district.
The statute also addresses factory-built residential structures. A jurisdiction cannot apply more restrictive aesthetic or dimensional standards to a factory-built ADU merely because of the method used to construct it.
That does not eliminate design review entirely.
Objective standards that do not meet the definition of a restrictive design or dimension standard may remain enforceable. Historic districts can also apply their own design standards and procedures, including requirements related to demolition.
Homeowners should therefore distinguish between prohibited ADU-specific barriers and lawful generally applicable design standards.
Building Code, Fire Code, Utilities, and Inspections Still Apply
One of the most important distinctions under Colorado ADU law is the difference between being allowed to have an ADU and being allowed to occupy a particular structure as housing.
HB24-1152 protects ADU land use in covered situations, but it does not exempt homeowners from construction and life-safety requirements.
The statute expressly preserves the ability of local governments to enforce locally adopted building, fire, utility, and stormwater codes.
Building Code Requirements
An ADU is a dwelling, not simply an accessory shed with furniture installed inside it.
The structure may need to meet requirements involving foundations, structural framing, insulation, energy performance, electrical systems, plumbing, heating, ventilation, stairs, guards, emergency escape, and other residential construction standards.
Requirements vary depending on the type of project.
A newly constructed detached ADU begins as residential construction, while a basement or garage conversion requires the building department to evaluate an existing space that may never have been designed for residential occupancy.
Existing conditions can make conversions more complicated than they initially appear.
For example, an unfinished basement may need additional emergency egress. A converted garage may require changes to insulation, flooring, windows, heating, fire separation, or structural components.
Fire Code and Fire Separation
Fire safety can affect both attached and detached ADUs.
Depending on the configuration and applicable codes, an ADU may need smoke alarms, carbon monoxide alarms, rated wall or ceiling assemblies, protected openings, emergency escape routes, or separation from a garage.
Fire department access can also influence site planning on certain properties.
A detached unit placed deep in a backyard may satisfy zoning setbacks but still need to comply with applicable emergency-access and fire-safety provisions.
The state ADU law does not override those life-safety requirements.
Water Service
Every legal ADU needs an acceptable source of domestic water.
In a municipality, the project may be served by the same public water provider as the primary residence. Whether the ADU can share an existing service line or requires upgrades depends on local utility standards and available capacity.
A local government may require a statement from a water or wastewater service provider regarding its capacity to serve the property as a condition of permitting the ADU.
This makes utility research an important early step.
A homeowner could spend significant money designing an ADU only to discover that the existing water service needs an expensive upgrade.
Sewer and Wastewater Service
Wastewater requirements can also affect feasibility.
A property connected to a public sewer may require review of the existing service line, connection configuration, or utility capacity.
Properties using septic systems can require more detailed analysis.
Adding another dwelling can increase the number of bedrooms, plumbing fixtures, or expected occupants on the property, potentially affecting septic capacity or permitting.
The exact requirements depend on the property and local wastewater rules.
Electrical and Other Utilities
ADUs also need safe electrical service.
Depending on the existing service capacity and project design, the property may need panel upgrades, new circuits, a separate meter, or additional utility infrastructure.
Gas service, heating equipment, internet service, and other utilities may also influence design.
Separate utility meters are not automatically required in every project, so homeowners should confirm the requirements with the local utility provider rather than assuming separate service is necessary.
Building Inspections and Final Occupancy
Construction permits typically lead to a series of inspections as work progresses.
The building department may inspect foundations, framing, electrical work, plumbing, insulation, mechanical systems, fire-safety components, and other regulated work before walls are closed or the project is completed.
After required inspections have been passed, the property may receive a certificate of occupancy or other local authorization allowing the new dwelling to be legally occupied.
This final step matters.
Finishing the physical construction does not automatically make the ADU legal housing if required permits and inspections have not been completed.
Colorado ADU Permit Process, Permit Fees, and Impact Fees
Colorado ADU law makes the land-use approval process more predictable in subject jurisdictions, but homeowners still need permits before creating a legal dwelling unit.
The exact application process varies by city or county. A detached backyard cottage may require more extensive site, structural, drainage, and utility documentation than an internal basement conversion.
The best approach is to determine whether the property can support the project before paying for complete construction drawings.
Confirm the Governing Jurisdiction and Zoning
Start by identifying which city or county controls land use for the property.
Do not rely only on the mailing address. A property with a city name in its postal address may actually be located in an unincorporated county area and subject to county zoning.
Once the jurisdiction is established, determine the zoning district and confirm that a single-unit detached dwelling is allowed.
For properties covered by HB24-1152, that determination establishes the starting point for the state’s ADU protections.
Review the Parcel Before Designing the Unit
The next step is a basic site analysis.
For a detached ADU, the site plan should account for the primary residence, garages, sheds, driveways, property lines, easements, setbacks, lot coverage, utilities, and any other improvements.
An attached or internal ADU requires a different review. Existing floor plans, structural conditions, egress, ceiling heights, plumbing locations, fire separation, and utility capacity may become more important.
The goal is to answer a simple question before detailed design begins: Is there a realistic, code-compliant place for this ADU?
Check Water, Sewer, and Utility Capacity
Utility feasibility should be investigated early.
HB24-1152 allows a local government to require confirmation from the applicable water or wastewater provider that sufficient capacity exists to serve the additional dwelling.
Depending on the property, an ADU may be able to share existing services or may require upgrades.
Possible costs can include larger water service lines, sewer work, electrical service upgrades, new meters, utility tap charges, or septic improvements.
These expenses can materially change the total project budget.
Prepare the Required Plans
Once zoning and utility feasibility are reasonably clear, the homeowner can move into design and construction documentation.
Requirements vary by project, but an application commonly needs a site plan, floor plans, elevations, structural information, energy-code documentation, and mechanical, plumbing, or electrical details.
Detached ADUs typically require a more detailed site plan because the new structure must be evaluated against lot lines, existing buildings, access, utilities, and other site conditions.
Conversions can require documentation of the existing structure as well as the proposed work.
Submit the ADU and Building Permit Applications
In a subject jurisdiction, the qualifying ADU itself must be handled through an administrative approval process using objective standards.
Building permits are still separate from that statewide land-use protection.
Fort Collins, for example, lists specific building-permit pathways for attached ADU conversions, new attached units, carriage houses, and detached ADUs. Its submittal requirements include residential permit documents, mechanical-system information, energy-code documentation, and other construction materials.
Boulder similarly requires a building permit for an ADU and requires applicants to submit additional ADU-specific information with the application.
Complete Required Inspections
An approved permit allows construction to move forward, but the project remains subject to inspections.
Inspectors may review foundation work, framing, plumbing, electrical systems, mechanical work, insulation, fire protection, and other code-regulated components.
Some inspections must occur before work is covered.
A homeowner should therefore coordinate inspection timing with the contractor rather than assuming everything can be inspected at the end.
Obtain Final Occupancy Approval
The project is not complete simply because construction appears finished.
All required inspections must be passed, corrections must be resolved, and the jurisdiction may require a certificate of occupancy or another form of final approval before the ADU can legally be occupied.
This is especially important for homeowners planning to rent the unit.
What Does an ADU Permit Cost?
There is no single statewide Colorado ADU permit fee.
Local governments may charge building permit fees, plan-review fees, utility fees, impact fees, and other generally applicable development charges.
HB24-1152 does not prohibit all fees. Instead, it allows reasonable and generally applicable fees while creating programs that can help qualifying jurisdictions reduce some ADU-related costs.
| Possible ADU Cost | What It Covers |
| Zoning or planning review | Land-use and site compliance |
| Building permit | Construction-code approval |
| Plan review | Technical review of submitted drawings |
| Utility fees | Water, sewer, electrical, or other service |
| Impact fees | Development impacts where legally applicable |
| Inspection fees | May be included in permit pricing or assessed separately |
| Professional plans | Architect, engineer, surveyor, or designer |
| Site work | Excavation, grading, drainage, access, and utilities |
These costs should be investigated before setting the construction budget.
Permit fees are only one part of the overall question of how much does an ADU cost, and utility or site work can sometimes have a greater financial impact than the permit itself.
Colorado ADU Grants, Financing, Property Taxes, and Housing Incentives
Making ADUs legal is only part of the housing challenge.
Construction can still require significant capital, particularly when a project involves new foundations, utility extensions, professional plans, or major alterations to an existing structure.
Colorado paired HB24-1152 with financial programs intended to reduce some of these barriers.
ADU Supportive Jurisdictions
Colorado allows local governments to become certified as ADU supportive jurisdictions.
To qualify, a jurisdiction must demonstrate compliance with the state’s ADU requirements and implement at least one additional strategy designed to encourage ADU construction or conversion.
Jurisdictions that are not otherwise subject to the mandatory provisions may also voluntarily participate.
Certification matters because some state ADU funding programs are tied to supportive jurisdictions.
ADU Fee Reduction and Encouragement Grants
HB24-1152 created the Accessory Dwelling Unit Fee Reduction and Encouragement Grant Program.
The program provides funding to supportive jurisdictions for activities such as developing pre-approved ADU plans, offering technical assistance, and waiving, reducing, or helping residents pay qualifying ADU fees and costs.
State budget documents show that grant activity has continued into the 2026–27 fiscal period, with funding intended to support local ADU construction and fee assistance.
The money does not mean every Colorado homeowner automatically receives a construction grant.
Assistance depends on whether the local jurisdiction participates, what programs it creates, available appropriations, and whether the homeowner or proposed ADU satisfies local eligibility requirements.
Colorado ADU Financing Programs
HB24-1152 also authorized state-supported financing programs through the Colorado Housing and Finance Authority.
CHFA announced ADU financing initiatives aimed at supporting construction or conversion for eligible low- and moderate-income borrowers or tenants in certified ADU supportive jurisdictions.
The programs include relending, credit enhancement, and interest-rate buydown structures.
Homeowners should check current program availability and eligibility before treating state-supported financing as part of their budget.
These programs can change as funding rounds open, close, or move through participating lenders.
Traditional ADU Financing Options
Homeowners who do not qualify for a state-supported program may consider conventional financing.
Common options include a home-equity line of credit, home-equity loan, construction loan, cash savings, or another loan secured against the property.
The appropriate option depends on the homeowner’s equity, income, credit, construction budget, and long-term plan for the unit.
A detached ADU built primarily for rental income may justify a different financing analysis than a basement conversion intended for an aging parent.
Loan payments should also be evaluated against realistic project costs rather than expected construction costs alone.
Design, permits, utility work, financing charges, insurance, site work, and contingency funds all belong in the budget.
Property Tax Considerations
Adding a permitted ADU creates a substantial improvement to a property and may affect its assessed value.
The exact effect on the property tax bill depends on the county assessor’s valuation and the applicable tax rates.
Homeowners should not assume that an ADU will leave the property’s tax assessment unchanged.
Before construction, it can be useful to ask the county assessor how newly completed residential improvements are typically reflected in future assessments.
The ADU may also affect insurance costs and rental-income tax reporting, depending on how the unit is used.
Why Colorado Is Encouraging ADUs
The state’s ADU policies are ultimately intended to support more than individual construction projects.
Accessory dwelling units can add housing within existing neighborhoods without requiring every parcel to be replaced with a larger multifamily development.
They can provide long-term rental housing, multigenerational living arrangements, workforce housing, accessible housing, or a smaller residence for someone who wants to age in place.
The state grant program specifically allows support to be targeted toward low- and moderate-income households, affordable units, accessible or visitable ADUs, and long-term workforce rentals.
That connection between land-use reform and financial support is an important part of Colorado’s broader ADU strategy.
Frequently Asked Questions About Colorado ADU Law
Can I build an ADU on any residential property in Colorado?
No. Colorado ADU law does not make every residential parcel automatically eligible for an accessory dwelling unit.
The strongest statewide protections apply within subject jurisdictions and are tied to locations where single-unit detached dwellings are permitted. Property-specific issues such as water and sewer availability, easements, flood hazards, historic regulations, and other lawful development standards can still affect the project.
Homeowners outside a subject jurisdiction may still be able to build an ADU if the local city or county independently permits one.
Does Colorado law allow one ADU on a single-family lot?
In a subject jurisdiction, HB24-1152 generally requires one ADU to be allowed as an accessory use to a single-unit detached dwelling wherever that type of primary dwelling is permitted.
The ADU must still satisfy applicable objective zoning, building, safety, utility, and site requirements.
The law protects the opportunity to construct the unit. It does not guarantee approval of every proposed design or location on the parcel.
Does an ADU in Colorado require the owner to live on the property?
A subject jurisdiction generally cannot require continuing owner occupancy of either the ADU or another dwelling on the property.
There are limited exceptions.
A jurisdiction may require an applicant to demonstrate residence on the property when applying to construct or convert an ADU, except when the ADU and primary dwelling are constructed simultaneously. Owner residency may also be required as part of a local short-term rental licensing system.
Does Colorado require an extra parking space for an ADU?
Generally, no new off-street parking space can be required solely because a qualifying ADU is being created.
Local governments may be able to designate an existing parking space for the ADU, and the statute includes a narrow exception allowing one new space when specific conditions involving existing parking, local zoning, and prohibited on-street parking are all present.
Homeowners should therefore check the parcel rather than assuming parking is either always required or completely irrelevant.
How large can an ADU be in Colorado?
Colorado does not impose one universal maximum ADU size.
HB24-1152 protects a usable size range by treating a local rule as restrictive if it fails to permit ADUs between 500 and 750 square feet.
Local governments may allow larger units, and many do.
Boulder, for example, currently permits standard detached ADUs up to 800 square feet and provides different limits for attached, affordable, and certain historic-property ADUs.
The actual maximum for a property should therefore be confirmed through the current local zoning code.
Can an HOA prohibit an ADU in Colorado?
An HOA in a subject jurisdiction or ADU supportive jurisdiction generally cannot enforce a declaration, bylaw, or rule that restricts ADUs in a way prohibited by Colorado’s statutory framework.
HB24-1152 preserves reasonable HOA restrictions, however.
A reasonable restriction cannot unreasonably increase construction costs, effectively prohibit construction, or eliminate the owner’s ability to build an ADU consistent with state law.
Homeowners should still review the declaration, covenants, architectural guidelines, and other governing documents before starting design.
Can I use my Colorado ADU as a short-term rental?
Not automatically.
HB24-1152 allows cities and counties to continue regulating short-term rental use of ADUs.
Local rules can be substantially more restrictive than the rules governing ordinary long-term occupancy.
Boulder restricts short-term rental use on properties with newer ADUs, Colorado Springs prohibits short-term rentals on properties with ADUs subject to grandfathered exceptions, and Fort Collins restricts newer ADUs from short-term rental use.
A homeowner planning to use rental income to finance an ADU should verify short-term rental eligibility before relying on nightly-rental projections.
Do I still need a permit under Colorado ADU law?
Yes.
HB24-1152 does not make ADUs permit-free.
A qualifying project may receive use-by-right protection and administrative zoning approval, but building permits, utility approvals, code compliance, inspections, and final occupancy approval can still be required.
Even an existing basement or accessory structure with little physical work may need a change-of-use or building permit before it can legally become a separate dwelling.
Check State Protection and Local Requirements Before Building
Colorado ADU law gives homeowners in covered communities substantially more protection than they had under a purely local system.
HB24-1152 limits several barriers that could previously make an ADU impractical, including discretionary approval, continuing owner-occupancy rules, automatic parking mandates, restrictive lot-size requirements, excessive setbacks, and certain design standards.
Those protections do not eliminate local planning or construction requirements.
Before committing to a project, confirm whether the property falls within the statewide framework, identify the correct city or county, check the zoning district, review utilities and site constraints, and determine which permits and inspections will be required.
A workable Colorado ADU project should move through the process in this order:
State law → jurisdiction → parcel → zoning → utilities → ADU design → permits → construction → inspections → legal occupancy.
Following that sequence helps homeowners avoid designing a unit around assumptions that later conflict with an easement, utility limitation, historic rule, building code, or local development standard.
Colorado has made accessory dwelling units easier to pursue, but the strongest projects still begin with careful property research before construction starts.