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.
Arvada’s real rules, taxes and rents — read from the codified ordinance, every figure sourced and dated. Here: rents floored at $1,754/mo. Run your own numbers below, free.
Read from the Arvada Land Development Code itself — the operative legal text, not a website summary. Arvada is an HB24-1152 subject jurisdiction: since June 30, 2025, Colorado law guarantees one ADU by right on any lot with a single-family home here.
| Maximum ADU size | By lot size: 600 sq ft (lot 6,000 sf or less); 850 (to 12,499 sf); 1,000 (to 1 acre); 1,200 (over 1 acre)verified September 2026Arvada Land Development Code §5-1-5-2the ordinance textTable 5-1-5-2: Maximum Floor Area of Accessory Dwelling Unit — Lot Size / Maximum Floor Area: 6,000 sf. or less — 600 sf.; Greater than 6,000 sf. and up to 12,499 sf. — 850 sf.; 12,500 sf. to 1 acre — 1,000 sf.; Greater than 1 acre — 1,200 sf. |
| Size relative to the main house | 40% of the principal home's living space; up to 50% if built within the existing home's footprint (incl. basement)verified September 2026Arvada Land Development Code §5-1-5-2the ordinance textADUs shall be: a. No larger than 40 percent of the living space of the principal building; and b. Within the lot size and floor area ranges set out in Table 5-1-5-2 [...] The limitations of Subsection E.1., above, shall not apply to ADUs that are located within the footprint of an existing home as long as the ADU is not larger than 50 percent of the floor area of the principal dwelling unit, including the basement. |
| Height limit | 30 ft in R6, R13, R24, and RN-32.5 zoning districts; 25 ft in RN-12.5, RN-7.5, RN-6, and RN-4 (single-family) subdistrictsverified September 2026Arvada Land Development Code §2-1-5-10the ordinance textTable 2-1-3-3A: 'Max. Height, ADU (detached) 30 ft. 25 ft. 25 ft. 25 ft. 25 ft. 25 ft. -' (RN-32.5 / RN-12.5 / RN-7.5 / RN-6 / RN-4 / RN-D single-family / RN-D duplex); Tables 2-1-3-4A, 2-1-3-5A, 2-1-3-6A: 'Max. Height, ADU (detached) 30 ft. -' (R6, R13, R24 residential column) |
| Owner occupancy | Yes — the owner must occupy either the main house or the ADU (the Director may waive this for temporary absences under one year, after two years of permitted use)verified September 2026Note: Arvada is an HB24-1152 subject jurisdiction. Since June 30, 2025, state law limits such cities to confirming the owner lives on the lot when the ADU application is filed (and to regulating short-term rentals); a standing owner-occupancy rule on a long-term-rental ADU is no longer enforceable. The ordinance text may predate that change — confirm current practice with the planning department.Arvada Land Development Code §5-1-5-2the ordinance textK. Owner Occupancy. 1. The property owner, as reflected in title records and evidenced by voter registration, vehicle registration or other similar means, must occupy either the principal dwelling unit or ADU. 2. The Director may waive this requirement for temporary absences of less than one year provided that the owner has maintained the permitted use for a minimum of two years and submits proof of the temporary absence. |
| Extra parking | 1 (may be tandem with the home's required spaces)verified September 2026Arvada Land Development Code §5-1-5-2the ordinance textOne on-site parking space shall be required for an ADU, in addition to any required parking for the principal dwelling unit. The required parking space may be in tandem with other required spaces. |
Source: Arvada Land Development Code, §2-1-5-10 · ordinance text retrieved 2026-08-25, re-verified September 2026 · open “the ordinance text” under any figure to read the exact sentence it comes from.
Arvada’s size cap is conditional rather than a single number: by lot size: 600 sq ft (lot 6,000 sf or less); 850 (to 12,499 sf); 1,000 (to 1 acre); 1,200 (over 1 acre) — worth reading closely before sizing a unit.
The owner must live on the property (main house or ADU) — common across Colorado (11 of the 14 codes we’ve read require it), and the rule that most often shapes rental plans. Note: Arvada is an HB24-1152 subject jurisdiction. Since June 30, 2025, state law limits such cities to confirming the owner lives on the lot when the ADU application is filed (and to regulating short-term rentals); a standing owner-occupancy rule on a long-term-rental ADU is no longer enforceable. The ordinance text may predate that change — confirm current practice with the planning department. Parking: 1 (may be tandem with the home's required spaces).
What an ADU adds to the tax bill in Arvada, and the conservative floor on what it rents for.
Levies: Jefferson County Assessor, 'Tax Authority Information and Reports' — 2025 Tag with Mill Levy All; 2025 Tax Authorities with Mill Levy All; 2024 Tag with Mill Levy and Authorities All (used only to determine which authorities compose each tag code; composition confirmed unchanged for 2025 because summing the 2025 per-authority mills for this exact authority set reproduces the 2025 tag total of 97.4410 exactly). 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 Arvada. 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
≈ $2,800–$3,500 / month fully financed
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 Arvada Land Development Code permits accessory dwelling units (§2-1-5-10), subject to the size, height, setback and use rules quoted above from the ordinance text. Arvada is also an HB24-1152 subject jurisdiction, so since June 30, 2025 state law requires one ADU to be allowed on any lot with a single-family home. 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 Arvada 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 Arvada Land Development Code: By lot size: 600 sq ft (lot 6,000 sf or less); 850 (to 12,499 sf); 1,000 (to 1 acre); 1,200 (over 1 acre). Both Olerra Flex Flats — the 490 and the 735 — are designed to fit typical Colorado caps; check the rules table above for the exact ordinance text.
Per the ordinance: Yes — the owner must occupy either the main house or the ADU (the Director may waive this for temporary absences under one year, after two years of permitted use).
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 $674 per year for every $100,000 of value the ADU adds, using the local mill levy split across Colorado's TY2026 school (7.05%) and local-government (6.80%) assessment rates.
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 — Arvada, CO. Data updated August 25, 2026. https://www.olerra.com/adu-calculator/arvada/ <a href="https://www.olerra.com/adu-calculator/arvada/">Arvada ADU rules & costs</a> Data as of August 25, 2026, the oldest figure on the page.
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 September 2026. Olerra pricing: published all-in project ranges, September 2026. Corrections: sales@olerra.com.
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