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.
Platteville’s real rules, taxes and rents — read from the codified ordinance, every figure sourced and dated. Here: a HUD benchmark rent of $1,238/mo for a 1-bed. Run your own numbers below, free.
Read from the Platteville Code Of Ordinances itself — the operative legal text, not a website summary. Platteville 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 | 75% of the principal dwelling's floor area (no fixed square-foot cap).verified October 2026Platteville Code Of Ordinances §16-3-20the ordinance textSec. 16-3-20(c) Standards, (1): "Each ADU shall comply with all applicable accessory structure standards and underlying development standards for the applicable zone district. If the accessory structure standards are stricter than the standards for principal structures, the ADU shall comply with the principal structure standards, except that each ADU shall be subordinate to and no larger than seventy-five percent (75%) of the square feet of the principal dwelling unit on the lot on which it is located." |
| Owner occupancy | Yes, but only as of the date the ADU building permit application is filed — not an ongoing requirement after that.verified September 2026Platteville Code Of Ordinances §16-3-20the ordinance textThe property owner shall reside on the property on the date a building permit application is filed for the ADU. |
| Extra parking | 1 additional spaceverified September 2026Platteville Code Of Ordinances §16-3-20the ordinance textEach ADU shall have one (1) designated off-street parking space, which may include an existing driveway, garage or tandem parking space. |
Source: Platteville Code Of Ordinances, §16-3-20 · ordinance text retrieved 2026-10-22, re-verified October 2026 · open “the ordinance text” under any figure to read the exact sentence it comes from.
Platteville’s size cap is conditional rather than a single number: 75% of the principal dwelling's floor area (no fixed square-foot cap). — worth reading closely before sizing a unit.
Owner occupancy: Yes, but only as of the date the ADU building permit application is filed — not an ongoing requirement after that.
Plan for 1 dedicated off-street space beyond the main house’s parking — on a tight lot, often a bigger siting constraint than the size cap.
Property tax runs lighter than most of the state here: 64.576 mills total in the example tax area (Weld County tax area 0180), about 28% below the median of the Colorado tax areas we track (levies vary by parcel).
What an ADU adds to the tax bill in Platteville, and the federal benchmark for what it rents for.
Levies: Weld County Assessor, 2025 Mill Levy Report (Tax District and Authority Report) — example: Weld County tax area 0180; levies differ between tax areas inside Platteville; check your parcel with the county assessor. Rates: Colorado DOLA, TY2026 — the 10% reduction on the first $700,000 of value applies to the local-government portion, once per property. Rents: HUD Fair Market Rents, huduser.gov.
Two ways to build the same unit in Platteville. 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 Platteville, the 490 needs a main home of at least 654 sq ft (the 75% rule)
≈ $2,800–$3,500 / month fully financed
In Platteville, the 735 needs a main home of at least 980 sq ft (the 75% rule)
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 Platteville Code Of Ordinances permits accessory dwelling units (§16-3-20), subject to the size, height, setback and use rules quoted above from the ordinance text. Platteville 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 Platteville 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 Platteville Code Of Ordinances: 75% of the principal dwelling's floor area (no fixed square-foot cap). The Olerra Flex Flat 490 needs a main home of at least 654 sq ft (the 75% rule); the 735 needs a main home of at least 980 sq ft (the 75% rule). The free property check confirms what fits on your lot.
Per the ordinance: Yes, but only as of the date the ADU building permit application is filed — not an ongoing requirement after that.
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.
Roughly $443 per year for every $100,000 of value the ADU adds (for a home already worth $700,000 or more; a little less below that, because 10% of the first $700,000 of value is exempt from the local portion), in the example tax area shown above: Colorado's TY2026 school (7.05%) and local-government (6.80%) assessment rates on the latest certified (TY2025) levy, a mixed-year estimate. Levies differ between tax areas, so check your parcel with the county assessor.
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 — Platteville, CO. Rules last verified October 22, 2026 against the codified ordinance; tax example: tax year 2025 levy, collected 2026 (Weld County tax area 0180); page released October 22, 2026. https://www.olerra.com/adu-calculator/platteville/ <a href="https://www.olerra.com/adu-calculator/platteville/">Platteville ADU rules & costs</a> Page released October 22, 2026 · rules last verified October 22, 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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