Colorado ADU Pro
Colorado ADU rules database

Check your city before you call a builder.

Colorado’s ADU law opened the door, but your city still controls the details that make or break a project: setbacks, size, parking, utilities, HOA review, and permit steps. Use this database to see what to check first.

14Denver metro cities tracked
2025State ADU baseline in effect
September 21, 2026Last reviewed

The state rule, in plain English

HB24-1152 requires many covered Colorado jurisdictions to allow at least one ADU on eligible single-unit detached lots through administrative approval. That does not mean every property is automatically buildable. It means your first question changes from “Does my city allow this?” to “What local standards do I need to satisfy?”

Use this as a starting point, not legal advice. Local code, utility providers, HOA documents, floodplain rules, historic review, and building permits still matter. Each city row links to a local guide with more homeowner context.
Denver Rear 35% lot placement, form standards, STR rules Aurora UDO implementation, zone district, lot layout Arvada Lot size, existing garage condition, setbacks Lakewood Slope, W Line proximity, drainage, utility run Westminster County side, lot width, US-36/Boulder rental demand Thornton Lot depth, newer subdivision layout, utility path Broomfield HOA, open-space adjacency, utility connections Golden Historic review, slope, access, wildfire interface Highlands Ranch HOA design review, walk-out potential, covenants Centennial Lot coverage, setbacks, DTC rental demand Littleton Historic/downtown context, mature trees, lot access Parker HOA review, lot size, utility distance Englewood Lot coverage, alley access, hospital/commuter demand Castle Rock Slope, drainage, HOA, utility run length

Search the city rules tracker

Search by city, county, or issue. Start with the “what to check first” column; that is usually where a homeowner saves the most time and money.

CityCurrent readOwner occupancyParkingSizeBest ADU fitWhat to check first
Denver
Denver
 Allowed citywide Owner at completion check Usually no new space Up to 1,000 sq ft in some zones Alley carriage house, basement ADU, garage conversion Rear 35% lot placement, form standards, STR rules
Aurora
Arapahoe / Adams / Douglas
 Rules expanding under HB24-1152 No long-term owner-occupancy focus Usually no new space Often 800 sq ft baseline Basement ADU, detached cottage, garage conversion UDO implementation, zone district, lot layout
Arvada
Jefferson / Adams
 Strong suburban candidate Check current city rule Usually no new space Check local standards Garage conversion, basement ADU, detached cottage Lot size, existing garage condition, setbacks
Lakewood
Jefferson
 Strong suburban candidate Check current city rule Usually no new space Check local standards Walk-out basement, detached cottage, garage conversion Slope, W Line proximity, drainage, utility run
Westminster
Adams / Jefferson
 Subject-jurisdiction style review Check current city rule Usually no new space Check local standards Detached cottage, garage conversion, basement ADU County side, lot width, US-36/Boulder rental demand
Thornton
Adams
 North metro growth market Check current city rule Usually no new space Check local standards Detached cottage, basement ADU Lot depth, newer subdivision layout, utility path
Broomfield
Broomfield
 City-county hybrid Check current city rule Usually no new space Check local standards Detached cottage, basement ADU HOA, open-space adjacency, utility connections
Golden
Jefferson
 Mountain-adjacent constraints Check current city rule Usually no new space Check local/historic rules Walk-out basement, garage conversion Historic review, slope, access, wildfire interface
Highlands Ranch
Douglas
 HOA-heavy; state law changed the baseline Check current county/metro district rule Usually no new space Check local standards Walk-out basement, internal conversion HOA design review, walk-out potential, covenants
Centennial
Arapahoe
 Large-lot opportunity Check current city rule Usually no new space Check local standards Detached cottage, basement ADU Lot coverage, setbacks, DTC rental demand
Littleton
Arapahoe / Jefferson / Douglas
 Premium established neighborhoods Check current city rule Usually no new space Check local standards Detached cottage, basement ADU, garage conversion Historic/downtown context, mature trees, lot access
Parker
Douglas
 Large lots plus HOA review Check current town rule Usually no new space Check local standards Detached cottage, multigenerational suite HOA review, lot size, utility distance
Englewood
Arapahoe
 Compact established lots Check current city rule Usually no new space Check local standards Garage conversion, basement ADU, small detached cottage Lot coverage, alley access, hospital/commuter demand
Castle Rock
Douglas
 Hillside and HOA review matter Check current town rule Usually no new space Check local standards Walk-out basement, detached cottage Slope, drainage, HOA, utility run length

Want a property-specific read?

Answer a few questions about your city, lot, HOA, and goals. You will get a clearer sense of the ADU path worth exploring before you pay for plans or start comparing builders.

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How we keep this useful

This database is built for homeowner decisions, so it focuses on the questions people actually ask before spending money: “Can I do this here?”, “What might block me?”, “What type of ADU fits my property?”, and “What should I ask a builder or designer?”

  • State-law baseline is checked against official Colorado HB24-1152 and DOLA guidance.
  • City rows link to local guide pages for more detail and next-step questions.
  • Rows are written in plain English, with cautious language where city implementation can change.
  • Next expansion: Boulder, Longmont, Fort Collins, Colorado Springs, Wheat Ridge, Commerce City, Northglenn, Lafayette, Louisville, Loveland, Greeley, and Pueblo.

Official state sources: Colorado HB24-1152 and DOLA ADU law summary.