ADUs are allowed in FirestoneTypes:DetachedInternal
Types:DetachedInternal
Accessory Dwelling Unit (ADU) Rules for Firestone, CO
Is your property eligible for an ADU?
# of Properties
10,454
Owner-occupied
87%
Zoning districts
39
Avg Home Value
$540,751
Median Lot Size
0.18 acres
Avg Income
$119,117
Residential Types:
10,454 housing units
Residential
100%
Zoning Districts:
26,632 parcels · 39 districts
R-B
31%(8,289)
R-A
30%(8,091)
R-1
9%(2,525)
R-C
9%(2,382)
Other
20%(5,345)
ADU Rules
What can you build in Firestone, CO?
Firestone, CO follows state and local rules for Accessory Dwelling Units. Here is a concise overview of the local rules.
Eligibility
- –Internal / Attached ADU: By Right
- –Detached ADU: By Right
Interior / Attached ADU Size Limits
- –Internal/attached ADU maximum size: 900 sq ft cap
- –Internal/attached ADU maximum size: 33% of principal dwelling habitable floor area
Detached ADU Size Limits
- –Maximum size of 900 sq ft for a detached ADU
- –Maximum size of 33% of principal dwelling habitable floor area for a detached ADU
Max Units
- –Single-family detached: 1 ADU/lot
- –Duplex or multifamily: 0 (not permitted)
Owner Occupancy
- –No owner-occupancy requirement for ADUs.
Parking
- –0 spaces per ADU if the lot has an existing single-family detached house and the abutting street allows on-street parking; otherwise 1 space per ADU. Off-site parking not allowed; parking required for both principal and ADU.
ADU State Law
What can you build in Colorado?
- –ADUs must be approved based on objective standards; no discretionary hearings allowed.
- –Historic properties: Local historic review may still apply in designated historic districts.
- –Exempt parcels: ADUs are not required to be allowed on parcels without adequate water/sewer, in floodways, or on certain historic properties.
- –HOAs cannot prohibit ADUs: HOA rules that conflict with the state ADU law are void.
- –Parking exceptions exist: In rare cases, one parking space may be required if there is no existing off-street parking and on-street parking is prohibited.
- –Local rules still matter: Building code, fire code, utility capacity, and life-safety standards still apply.
- –More permissive is allowed: Municipalities may allow larger ADUs, multiple ADUs, or additional housing types beyond what the state requires.
- –Local zoning controls whether ADUs are allowed at all.
- –HOA rules may still apply.
- –More permissive local rules are allowed.
What's allowed on your lot?
These are the municipality-wide rules. What's allowed on a specific property also depends on state laws, setbacks, floor area ratio, lot coverage, environmental constraints, topography, and other property-specific factors. Search your address on FutureLot to see what's allowed on your property.
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ADU rules in other Colorado municipalities
Rules change at the town line. Check the municipality your property is actually in.
Weld County