You’re sitting at your kitchen table with a plat map and a cup of cold coffee, wondering: can I actually build an ADU here? And if I can, how much rental income will I actually make?
The problem is that the answer depends entirely on which Colorado city you live in. HB24-1152, the state law that legalized ADUs across Colorado, set a floor—certain things are now legal statewide. But each city built its own rules on top of that floor. Denver’s rules are different from Colorado Springs’ rules. Colorado Springs’ rules are different from Fort Collins’. And those differences matter enormously for what you can build, whether you can rent it out, and how much money you’ll actually make.
This guide breaks down the specific, current rules in three Front Range markets: Denver, Colorado Springs, and Fort Collins. By the end, you’ll know exactly what’s allowed in your city—and whether your specific ADU project is even legal.
One State Law, Three Very Different Cities
HB24-1152 went into effect on July 1, 2024. It was Colorado’s historic ADU legalization—basically saying that cities can no longer ban ADUs in single-family zones. But “cities can no longer ban them” doesn’t mean “all cities treat them the same way.”
The state law set the minimum standard. But municipalities have the authority to impose additional requirements: size caps, setback rules, parking mandates, owner-occupancy requirements, or permitting timelines. Some cities are using that authority to encourage ADUs aggressively. Others are using it to slow them down.
The result is a patchwork. For the full HB24-1152 text and state-level details, check Olerra’s state law article. But for how it actually plays out in Denver, Colorado Springs, and Fort Collins—the three largest Front Range markets—keep reading.
Colorado Springs: The New Ordinance (April 2025)
Colorado Springs just became one of the most ADU-friendly large cities in Colorado. City Council approved Ordinance #25-45 on April 8, 2025, and it fundamentally changed what’s possible on a Colorado Springs property.
Owner-Occupancy Requirement: ELIMINATED
This is huge. Under the previous rules, you had to live in either your primary home or the ADU. You couldn’t rent both simultaneously. That rule is gone. Now you can own a Colorado Springs property, live somewhere else, and rent both the primary home and the ADU to tenants. That opens up investment possibilities that didn’t exist before.
Size Limits
Detached ADUs are allowed up to 1,250 square feet—or 50% of your primary residence’s square footage, whichever is smaller. For typical Colorado Springs homes (1,500–2,500 sq ft), that means you’re looking at 750–1,250 sq ft ADU units. These are not tiny. You can build a full 1-bedroom with a den, or a 2-bedroom with a small living room. The density is real.
For primary homes under 1,500 sq ft, the ADU caps at 750 sq ft—still a full, rentable 1-bedroom unit.
Zoning and Permitting
ADUs are now permitted in ALL zone districts where single-family detached homes are allowed. No special overlay zones, no requirement to apply to the Planning Commission. It’s a ministerial approval at the staff level—meaning if your plans meet code, staff issues the permit. No discretionary review process. That translates to faster timelines and more predictability.
What This Means for Investors
Colorado Springs just became a serious rental income market. The removal of owner-occupancy rules means you can pursue a pure investment strategy: buy a property, renovate it (or build an ADU on it), and rent both units. You’re not locked into living there yourself. The 1,250 sq ft size cap is generous—you can build a real rental unit, not a studio or efficiency.
Combined with Colorado Springs’ more modest home prices compared to Denver or Boulder, the ROI potential is significant. You can buy a property for $400,000–$500,000, add a $250,000–$350,000 modular ADU, and generate $2,000–$2,400/month in additional rental income while the total property cost is lower than a comparable home in Denver.
Fort Collins: The Early Adopter’s Advantage
Fort Collins moved faster than any other Colorado city. On February 14, 2025, the city updated its Land Use Code to not only comply with HB24-1152, but to actually exceed the state minimums—making Fort Collins the most ADU-friendly of the three Front Range markets.
Zoning: Everywhere
ADUs are allowed in literally every zone district where single-family homes are permitted. No restrictions based on neighborhood character, no special overlays, no “only on corner lots.” If single-family is allowed, ADU is allowed.
Permitting: Staff Level, No Commission
Fort Collins skipped the Planning Commission review entirely. ADU permits are approved administratively—meaning the planning staff reviews your application against code, and if it complies, you get a permit. No public hearing, no discretionary review. Staff approval timelines: 2–4 weeks for a straightforward modular ADU project.
Parking: No Mandate
This is the quiet killer of ADU projects in many cities. Parking requirements can add $10,000–$30,000 to a project if you need to construct dedicated parking. Fort Collins eliminated this for ADUs. No minimum parking requirement. You’re not forced to build a concrete pad or garage addition if you don’t want to. This single rule change probably unlocks another 20–30% of properties that were previously undevelopable.
Owner-Occupancy: Not Required
Same as Colorado Springs—you can rent both the primary home and ADU simultaneously if you choose.
Rental Income Potential in Fort Collins
Fort Collins has tight rental vacancy rates and strong tenant demand. 1-bedroom apartments in Fort Collins average $1,639/month (per recent market data). A well-finished modular ADU in a desirable neighborhood hits $2,000–$2,200/month easily. Some custom builds rent for $2,500–$3,000. For detailed rental income data by city and floor plan type, Olerra’s ADU ROI article breaks down how long it takes to recover your investment in Fort Collins specifically.
Why Fort Collins Matters
Fort Collins is where you go if you want the absolute minimum friction with permitting and maximum rental income upside. The city has actively chosen to support ADUs, and it shows in the rules. Faster staff approval, zero parking requirements, any zoning, no owner-occupancy mandate. This is the ADU-friendly playbook every other Colorado city should follow—and some are.
Denver: Comprehensive Rules, STR Watch-Outs
Denver is different. The city has allowed ADUs under its zoning code for years (well before HB24-1152). But Denver’s rules are more intricate, and there’s one provision that catches a lot of would-be ADU builders: short-term rental restrictions.
ADU Legality: City-Wide
Denver permits ADUs in all zones where single-family homes are allowed. Your property doesn’t have a special zoning restriction. The process is thorough but familiar to Denver planners who’ve been reviewing ADU projects for five+ years.
The Short-Term Rental Trap
This is where Denver diverges from Colorado Springs and Fort Collins. Colorado state law says cities can require owner-occupancy IF the ADU is being used as a Short-Term Rental (Airbnb, VRBO, etc.). Denver has exercised that authority: if you plan to Airbnb your ADU, you must live in the primary home. You cannot Airbnb a unit you don’t live nearby.
But—and this is critical—if you plan to do traditional long-term rental (12-month leases), owner-occupancy is not required in Denver. You can live anywhere and rent the ADU on a traditional lease.
So if your strategy is “buy a property, do long-term rental, collect $2,000/month” that works fine in Denver. If your strategy is “I want to Airbnb this to maximize short-term rental income,” Denver requires you to live in the primary home.
Permitting Timeline and Costs
Denver’s permitting process is thorough. Typical timeline: 4–8 weeks for a straightforward project. The city’s planning staff will do a detailed review of your plans, may ask for revisions, and moves carefully through inspections. That’s good for quality but slower than Fort Collins’ 2–4 week administrative approval.
Fees are also higher in Denver than Colorado Springs or Fort Collins. Plan on $5,000–$8,000 in permitting, impact, and planning review costs—compared to $2,000–$4,000 in other Front Range cities.
Why Denver Still Works
Denver’s tighter rules and higher costs are offset by strong rental demand and premium rents. Long-term rental rates in desirable Denver neighborhoods hit $2,200–$2,800/month for a 1-bedroom. If your ADU is located in an in-demand neighborhood (Highland, Baker, Cap Hill, South Pearl), you’ll achieve positive cash flow quickly despite the higher permitting costs.
For a deeper comparison of Denver, Boulder, and Colorado Springs zoning rules, including setback, height, and lot coverage requirements, Olerra’s Big Three cities article covers all the technical specifications.
The Key Differences That Actually Matter for Investors
Let’s cut through the weeds and focus on what actually affects your investment:
Short-Term Rental (Airbnb) Flexibility
Fort Collins and Colorado Springs have no owner-occupancy requirement. If Airbnb is your strategy, both cities allow it. Denver requires owner-occupancy for STRs. If you want to Airbnb your ADU in Denver, you have to live in the primary home. Winner for STR investors: Fort Collins and Colorado Springs.
Size Limits
Colorado Springs caps detached ADUs at 1,250 sq ft or 50% of primary residence size. Fort Collins has size limits that depend on your lot size (generous on larger lots). Both allow substantial units. Denver’s size limits are more restrictive (generally 750–1,000 sq ft), limiting your ability to build larger, premium units. Winner for size: Colorado Springs and Fort Collins.
Permitting Speed
Fort Collins: 2–4 weeks (administrative staff approval). Colorado Springs: 3–6 weeks (staff approval but slightly slower processing). Denver: 4–8 weeks (Planning Commission review possible). Winner for speed: Fort Collins.
Total Fees
Fort Collins and Colorado Springs: $2,000–$4,000 combined. Denver: $5,000–$8,000. Winner for cost: Fort Collins and Colorado Springs.
Rental Income Potential
Fort Collins: $2,000–$2,200/month long-term, tight vacancy, strong demand. Colorado Springs: $1,700–$2,000/month, moderate demand. Denver: $2,200–$2,800/month in desirable neighborhoods, competitive market, higher entry cost. Winner for absolute income: Denver. Winner for income-to-cost ratio: Fort Collins.
Choosing Your Market
Your ideal city depends on your investment priority.
If Your Priority Is Investment Rental Income with Minimal Friction: Fort Collins wins. Fast permitting, no size limits that matter, no parking requirements, no owner-occupancy, and strong rents ($2,000–$2,200) in a tight market. You spend the least time permitting and the least money on fees, and you recover your investment fastest.
If Your Priority Is Airbnb or Short-Term Rental Income: Fort Collins or Colorado Springs. Both allow STR without owner-occupancy requirements. Denver forces you to live there. If you want a hands-off investment property, the Springs or Fort Collins are your play.
If Your Priority Is Pure Income Upside and You Don’t Mind More Permitting Complexity: Denver. Rents are $300–$600/month higher than other Front Range cities. The permitting takes longer and costs more, but the rental income more than makes up for it. This works if you’re willing to be slightly more patient and you want the absolute highest rent ceiling.
If Your Priority Is Lower Overall Entry Cost and Quick Cash Flow: Colorado Springs. Home prices are lower than Denver or Fort Collins. The new Ordinance #25-45 removes all the biggest barriers (owner-occupancy, zoning restrictions, parking mandates). Rents are lower than Denver, but your property cost is lower too, so your cash-on-cash return is competitive.
If You’re Uncertain Which Option Fits Your Situation: Check the detailed ADU ROI article for income scenarios by city. It walks through the math for each market with actual rental rates and mortgage calculations.
Next Steps: Know Your Rules, Know Your Numbers
The good news is that ADUs are legal in all three Front Range markets. The great news is that all three have genuinely improved their rules in the last year. The smart move is to understand the specific regulations for your city, then run the financial numbers for your specific property.
Start by contacting your city planning department:
- “Can I build a detached ADU on my property? What are the size limits, setback requirements, and parking mandates?”
- “How long does ADU permitting typically take, and what are the fees?”
- “If I rent the ADU long-term, do I have to live in the primary home?”
- “Are there any local incentive programs (grants, fee waivers) available?”
Once you have those answers, you can model out the true cost of your project and the rental income potential. Most Colorado homeowners are surprised at how quickly a modular ADU achieves positive cash flow—but only if you understand your city’s specific rules.
Ready to explore what your ADU could cost and earn? Browse Olerra’s Flex Flat floor plan options—each designed to fit Colorado Front Range lots and zoning constraints. Then check out the complete Modular Homes Colorado guide to understand the full build timeline. Your perfect ADU is just waiting for the right plan and the right city.