ADUs are allowed in JohnstownTypes:DetachedInternal
Types:DetachedInternal
Accessory Dwelling Unit (ADU) Rules for Johnstown, CO
Is your property eligible for an ADU?
# of Properties
12,155
Owner-occupied
77%
Zoning districts
59
Avg Home Value
$419,853
Median Lot Size
0.16 acres
Avg Income
$138,634
Residential Types:
12,155 housing units
Other
100%
Zoning Districts:
26,767 parcels · 59 districts
R-1
44%(11,686)
PD-PR-R
14%(3,622)
PD-TRR-RMU
6%(1,587)
PD-CV-RMU
6%(1,581)
Other
31%(8,291)
ADU Rules
What can you build in Johnstown, CO?
Johnstown, 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
- –Maximum size of 50% of the principal dwelling unit’s floor area
Detached ADU Size Limits
- –Maximum ADU size is 1,000 sq ft or 50% of the principal dwelling’s floor area, whichever is smaller.
- –As a detached accessory building, the ADU is limited to 50% of the principal building’s footprint or 1,000 sq ft, whichever is smaller.
Max Units
- –Detached ADU (Secondary Building): 1 per lot; 2 per lot on lots over 40,000 sq ft. Duplex/multi-unit dwellings: 0 per lot.
Owner Occupancy
- –Owner with at least 50% ownership must occupy principal dwelling or ADU.
Parking
- –1 space/ADU (on-site); max = 140% of min; waivers for transit access, on-street parking on the block, or principal dwelling parking configuration; reductions include on-street credit (0.5 space per on-street space within 300 ft), alternative transportation (up to 50%), and administrative adjustment (up to 3 spaces or 10%).
Rental Restrictions
- –Short-term rentals prohibited; tenancy must be monthly or longer.
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