ADUs are allowed in KeystoneTypes:DetachedInternal
Types:DetachedInternal
Accessory Dwelling Unit (ADU) Rules for Keystone, CO
Is your property eligible for an ADU?
# of Parcels
4,009
Zoning districts
40
Avg Parcel Value
$1,096,611
Zoning Districts:
4,009 parcels · 40 districts
KR-PUD
71%(2,854)
B-1
6%(237)
CDM-PUD
2%(76)
SR-PUD
2%(71)
Other
19%(771)
ADU Rules
What can you build in Keystone, CO?
Keystone, 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
- –Maximum size of 1,000 sq ft on lots under 5 acres and 1,400 sq ft on lots 5 acres or larger (garage area excluded from ADU floor area).
Detached ADU Size Limits
- –Maximum detached ADU size: 1,000 sq ft on lots under 5 acres; 1,400 sq ft on lots 5 acres or more.
Owner Occupancy
- –Owner shall not occupy the restricted unit.
Parking
- –1 space per studio/1-bedroom ADU; 2 spaces per ADU with 2+ bedrooms; tandem parking allowed (outside or in a garage). Parking must be in a designated paved or graveled area. On a single-family lot with a permitted ADU, one required space may be within the setback if at least 5 feet from all property lines and compliant with code.
Rental Restrictions
- –Short-term rentals of the restricted unit are prohibited; if rented, it must be leased for at least six consecutive months to Qualified Occupant(s).
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.
Summit County