What Size ADU Can I Build in Colorado Springs?

The rule from Ordinance #25-45: an ADU may be as large as 50 percent of the primary structure or 1,250 square feet, whichever is less. And there is a floor for modest homes: if your house is under 1,500 square feet, you may build a 750-square-foot ADU even though 50 percent would allow less.

Worked examples make the rule obvious:

1,250 1,000 750 1,000 1,500 2,000 2,500 3,000 Primary house size (sq ft) Max ADU size (sq ft) 750 sq ft floor 50% of the house 1,250 sq ft cap 1,200 → 750 1,800 → 900 2,400 → 1,200 3,000 → 1,250
The size rule from Ordinance #25-45, with this page's worked examples marked. Source: City of Colorado Springs ADU standards.

For scale: 750 square feet is a full one-bedroom apartment; 1,000 to 1,250 comfortably fits two bedrooms. So the size rule accommodates a real dwelling on almost any lot, not just a studio.

Size interacts with three other standards. Height: a new detached ADU is capped at 16 feet (a garage converted to an ADU may reach 25 feet, which is what makes two-story carriage-house layouts possible; see garage conversion vs. detached). Placement: front yards are off-limits, and a detached unit needs a 5-foot rear setback with front and side setbacks matching the main house. And a helpful obscurity: the ADU does not count against your lot's total floor-area cap for accessory structures, so an existing shed or workshop does not shrink your ADU allowance.

In practice the 16-foot height cap means most new detached ADUs are single-story, so the square footage must fit the footprint your yard allows after setbacks: a 900-square-foot single-story unit needs roughly a 30-by-30 area of buildable rear or side yard. That is why deep lots find the size cap generous while tight lots are constrained by geometry long before they hit the legal maximum. Integrated ADUs sidestep the footprint problem entirely by using space the house already encloses, which also makes them the only option inside the wildfire overlay.

Bigger is not automatically better, either for budget or for rental math: local builders price detached construction per square foot (roughly $400 to $500 typical), while a 1-bedroom rents for about the same whether it is 700 or 900 square feet. The cost guide covers that trade-off. The complete standards live in the ordinance guide.