How to Choose an ADU Contractor in Colorado (Questions to Ask)
How to hire an ADU contractor in Colorado, the questions to ask, the red flags to avoid, how licensing works here, and modular versus site-built compared.
Westminster’s real rules, taxes and rents — read from the codified ordinance, every figure sourced and dated. Here: a HUD benchmark rent of $1,754/mo for a 1-bed. Run your own numbers below, free.
Read from the Westminster Code Of Ordinances itself — the operative legal text, not a website summary. Westminster is an HB24-1152 subject jurisdiction: since June 30, 2025, state law requires it to allow an ADU wherever it allows a single-family home, with administrative approval — the local standards below still apply.
| Maximum ADU size | 1,200 sq ftverified September 2026The City’s ADU building guide (REV 5, March 10, 2026) also allows up to 750 sq ft when the main home is under 1,500 sq ft, never larger than the main home. That allowance is not in the codified section, so confirm it with the City before relying on it.Westminster Code Of Ordinances §11-4-19the ordinance textThe maximum size for an accessory dwelling unit shall be 1,200 square feet, or 50 percent of the gross floor area of the principal dwelling unit, whichever is less. |
| Size relative to the main house | 50%verified September 2026Westminster Code Of Ordinances §11-4-19the ordinance textThe maximum size for an accessory dwelling unit shall be 1,200 square feet, or 50 percent of the gross floor area of the principal dwelling unit, whichever is less. |
| Minimum ADU size | 190 sq ftverified October 2026Westminster Code Of Ordinances §11-4-19the ordinance text(H) Size Requirements: (1) The minimum size for an accessory dwelling unit shall be 190 square feet. |
| Owner occupancy | No — Westminster's ADU standards contain no owner-occupancy requirementverified October 2026Westminster Code Of Ordinances §11-4-19the ordinance textSec. 11-4-19 (A)–(N), the full ADU section (Ord. 4272, 2024), and the code's ADU definition contain no owner-occupancy or residency requirement — at application or afterwards. |
| Short-term rental | Yesverified September 2026Westminster Code Of Ordinances §11-4-19the ordinance textShort Term Rental ... may be allowed in any type of Dwelling Unit as defined in Section 11-2-1, provided the following conditions have been met. |
| Extra parking | 0 (1 required only if the principal dwelling lacks existing off-street parking AND on-street parking is prohibited on that block)verified September 2026Westminster Code Of Ordinances §11-4-19the ordinance textOne new parking space is required for each accessory dwelling unit only if both of the following conditions exist. If none of the following conditions exist, no new parking spaces are required. |
| Setbacks | Front and side: same as principal dwelling; rear: same as other accessory buildings in the zone district, or 5 ft, whichever is greaterverified September 2026Westminster Code Of Ordinances §11-4-19the ordinance textAccessory dwelling units shall comply with the rear setbacks established for other accessory building types in the same zone district, or five feet, whichever is greater. |
Source: Westminster Code Of Ordinances, §11-4-19 · ordinance text retrieved 2026-08-25, re-verified October 2026 · open “the ordinance text” under any figure to read the exact sentence it comes from.
Westminster’s size cap is conditional rather than a single number: 1200 — worth reading closely before sizing a unit.
The cap is also relative: an ADU here may not exceed 50% of the main house, so a smaller primary home means a smaller buildable ADU.
Short-term rental of the ADU is permitted (see the licensing terms in the ordinance) — Colorado codes split almost evenly on this, and it changes the revenue math entirely.
Parking: 0 (1 required only if the principal dwelling lacks existing off-street parking AND on-street parking is prohibited on that block).
And Westminster is one of only 30 Colorado jurisdictions certified ADU Supportive, which makes residents eligible for CHFA’s state-backed ADU financing — an interest-rate buydown and credit enhancement offered through participating lenders. Most of the Front Range doesn’t have this lever.
The federal benchmark for what an ADU rents for in Westminster.
Rents: HUD Fair Market Rents, huduser.gov.
Two ways to build the same unit in Westminster. Both figures are all-in — design, permits, foundation, utility connections and installation.
Published Front Range ranges for a comparable one-off build, 2025–26
≈ $2,100–$2,600 / month fully financed
In Westminster, the 490 needs a main home of at least 980 sq ft under the code's 50% rule; the City's ADU guide also allows it beside a home of 490 to 1,499 sq ft (guide only, not in the code, so confirm with the City)
≈ $2,800–$3,500 / month fully financed
In Westminster, the 735 needs a main home of at least 1,470 sq ft under the code's 50% rule; the City's ADU guide also allows it beside a home of 735 to 1,499 sq ft (guide only, not in the code, so confirm with the City)
Olerra ranges: published all-in project pricing, September 2026 — site preparation, foundation, utility connections and permitting included.
Free and specific to you. Want to go further?
Yes. The Westminster Code Of Ordinances permits accessory dwelling units (§11-4-19), subject to the size, height, setback and use rules quoted above from the ordinance text. Westminster is also an HB24-1152 subject jurisdiction, so since June 30, 2025 state law requires it to allow an ADU wherever it allows a single-family home, with administrative approval; the local standards above still apply. Zoning district, lot size and setbacks still decide what fits on a specific lot — the free property check confirms yours.
Yes. An ADU is a new dwelling unit, so Westminster requires a building permit (plus any zoning or site-plan review the code calls for) before construction starts. Olerra's all-in price includes permitting, and factory-built units are inspected to the same building code as a site-built home.
Per the Westminster Code Of Ordinances: 1,200 sq ft. The City’s ADU building guide (REV 5, March 10, 2026) also allows up to 750 sq ft when the main home is under 1,500 sq ft, never larger than the main home. That allowance is not in the codified section, so confirm it with the City before relying on it. The Olerra Flex Flat 490 needs a main home of at least 980 sq ft under the code's 50% rule; the City's ADU guide also allows it beside a home of 490 to 1,499 sq ft (guide only, not in the code, so confirm with the City); the 735 needs a main home of at least 1,470 sq ft under the code's 50% rule; the City's ADU guide also allows it beside a home of 735 to 1,499 sq ft (guide only, not in the code, so confirm with the City). The free property check confirms what fits on your lot.
Yes — short-term rental of an ADU is permitted, subject to the licensing terms in the ordinance.
Per the ordinance: No — Westminster's ADU standards contain no owner-occupancy requirement.
A one-off site build with a general contractor typically runs about $500,000–$650,000 for a ~490 sq ft unit. Olerra's factory-built Flex Flats run $300,000–$365,000 (490) and $420,000–$465,000 (735) all-in — site preparation, foundation, utility connections and permitting included.
Same method, each city’s own ordinance. The Colorado hub lists every city, and the statewide ADU calculator covers any Colorado address.
Guides and real Colorado numbers from our team — a fresh pick every couple of weeks, or search for exactly what you need.
How to hire an ADU contractor in Colorado, the questions to ask, the red flags to avoid, how licensing works here, and modular versus site-built compared.
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Planning departments and journalists are welcome to reference this data.
Olerra ADU Cost Calculator — Westminster, CO. Page updated October 9, 2026; rules verified October 2026. https://www.olerra.com/adu-calculator/westminster/ <a href="https://www.olerra.com/adu-calculator/westminster/">Westminster ADU rules & costs</a> Page updated October 9, 2026. The oldest dated figure on the page is from August 25, 2026.
Planning estimates, not quotes or legal advice. Rules, fees, levies and rents change — confirm with the city and your lender before committing. Rules data: codified ordinance as of August 25, 2026, re-verified October 2026. Olerra pricing: published all-in project ranges, September 2026. Corrections: sales@olerra.com.
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