How many ADUs can I build in Broomfield and how big can they be?

One ADU per property zoned for single-unit residential use. Any ADU can be up to 500 square feet by right; larger ADUs are capped at the lesser of 50% of the principal dwelling's footprint (excluding garage/porch) or 800 square feet. Source: City and County of Broomfield Accessory Dwelling Units page and ADU FAQ handout (Planning Division, updated 11/4/25).

How long does an ADU building permit take to review in Broomfield?

Broomfield does not publish an ADU-specific line item on its Current Plan Review times list. An ADU is permitted through the Building Division's General Permit Application as a residential building permit, so the governing published timeline — 7 to 8 weeks (35-40 days), the same figure used for New House / Residential Building Permit reviews — applies. These are stated as goals, not guarantees; confirm current timing with buildingpermits@broomfield.org.

Accessory Dwelling Unit (ADU) Permit in Broomfield, Colorado

Verified

Required for construction of an accessory dwelling unit (ADU) on a single-unit-zoned property in the City and County of Broomfield. Governed by Ordinance No. 2265 (adopted September 9, 2025, effective September 16, 2025; BMC §17-04-089 / §17-32-160), aligning Broomfield's local ADU rules with the statewide ADU law (HB24-1152). Reviewed by the Planning Division for zoning/design and the Building Division for construction.

Verified 2026-07-03 · Source

$23.50Building Permit Fee — valuation-based (same schedule as new construction/addition)

When you need this permit

Maximum one (1) ADU per property zoned for single-unit residential use; no owner-occupancy requirement
ADU may be internal, attached, or detached (including new-build detached structures, Tiny Homes, and Manufactured Homes per BMC Chapter 17-04); travel trailers, RVs, and shipping/storage containers are prohibited as ADUs
Size limit: up to 500 sq ft by right; larger ADUs are capped at the lesser of 50% of the principal dwelling's footprint (excluding garage/porch/similar areas) or 800 sq ft
ADU design must be consistent with the principal dwelling; where no specific zoning design standard applies, the ADU must be clad in a material similar to the principal structure
ADU must tie into the principal dwelling's existing water and sewer connections — no separate water/sewer tap or license required; other utilities (electric, gas, phone, internet) arranged separately with utility providers
Homes on septic systems must coordinate with the Health Protection Division of Health and Human Services (publichealth@broomfield.org, 720-887-2220) to confirm septic capacity
ADU must meet the zone district's applicable setback requirements, except the ADU's side setback is never greater than the principal dwelling's side setback
No new parking required unless (a) adjacent streets disallow on-street parking AND (b) the property is outside a Parking Reduction Area — if both apply, 3 off-street spaces (2 for the principal unit, 1 for the ADU) must be demonstrated
A Declaration of Use must be recorded, stating the ADU's size/location and referencing ongoing BMC compliance
Building permit required using the Building Department's General Permit Application form; contact the Building Division to confirm supporting documents (an ADU Checklist is required as a supporting document)
Applicants should confirm HOA rules before submitting, since HOAs may impose additional restrictions

Required documents

Required
General Permit Application
Standard Broomfield Building Division permit application, used for ADU construction
Required
ADU Checklist
Supporting document required with the Building Permit application for ADUs
Required
Declaration of Use
Recorded document stating ADU size/location and BMC compliance obligation

Fee schedule

Fee type	Amount	Notes
Building Permit Fee — valuation-based (same schedule as new construction/addition)	$23.50 minimum ($1-$500 valuation), scaling per the published fee table; BMC 15-03-100 Table 1-A above $18,000	City and County of Broomfield Building Division Fee Schedule — ADUs are permitted through the same General Permit Application and fee structure as additions

Review timeline

35–40 business days

Broomfield’s published plan-review target

Inspection process

1
Foundation/Framing (detached ADU) or Framing (attached/internal)
Structural inspection appropriate to ADU type before concealment
2
Final
Completed ADU verified against approved plans and ADU Checklist, prior to occupancy

Tips

No dedicated 'ADU' or 'Accessory Dwelling Unit' entry appears on Broomfield's published 'Current Plan Review times' list (Review Timelines page / Building FAQ QID=329) — that list runs from like-for-like replacements (1-3 business days) up through 'New House' at 7 to 8 weeks, with no ADU-specific line item. Since an ADU (attached, internal, or new-build detached) is permitted through the Building Division's General Permit Application as a residential building permit — the same process and application used for new single-family construction — the governing published timeline is the 'New House' figure of 7 to 8 weeks (35-40 days), the same figure anchoring the verified Residential Building Permit.
ADUs are a Planning Division policy (zoning, size, setbacks, Declaration of Use) combined with a Building Division permit (construction) — expect to interact with both offices; the governing timeline above covers the Building Division's construction-permit review only.
Ordinance No. 2265 (September 2025) updated Broomfield's ADU rules specifically to conform to Colorado's statewide ADU law HB24-1152; if researching other Colorado jurisdictions, note that HB24-1152 sets a statewide floor but each city/county still adopts its own local implementing ordinance.

Frequently asked questions

How many ADUs can I build in Broomfield and how big can they be?: One ADU per property zoned for single-unit residential use. Any ADU can be up to 500 square feet by right; larger ADUs are capped at the lesser of 50% of the principal dwelling's footprint (excluding garage/porch) or 800 square feet. Source: City and County of Broomfield Accessory Dwelling Units page and ADU FAQ handout (Planning Division, updated 11/4/25).
How long does an ADU building permit take to review in Broomfield?: Broomfield does not publish an ADU-specific line item on its Current Plan Review times list. An ADU is permitted through the Building Division's General Permit Application as a residential building permit, so the governing published timeline — 7 to 8 weeks (35-40 days), the same figure used for New House / Residential Building Permit reviews — applies. These are stated as goals, not guarantees; confirm current timing with buildingpermits@broomfield.org.

Sources & verification

Verified against official sources. Last reviewed 2026-07-03.

Fees, timelines, and adopted codes are researched from each jurisdiction's published records — see how we verify. Requirements change and vary by project, so always confirm the current details with the Broomfield building department before you submit. PermitBase is an independent reference and is not affiliated with any government agency.

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