Boulder County, CO zoning map, flood zone and property lines by address
Free, no account. Or open the Colorado map and tap a lot.
Towns in Boulder County: Boulder, Longmont, Lafayette.
Flood zone by address
ParcelSheet reads FEMA's National Flood Hazard Layer at the lot: the zone, whether it is a high risk area where lenders ask for flood insurance, and the base flood elevation where FEMA lists one. FEMA's countywide study for Boulder County has 156 FIRM panels, the newest effective October 2024; no coastal V zones are mapped in it.
The official panel and any Letter of Map Amendment are at FEMA's Map Service Center. An elevation certificate for a Boulder house comes from a licensed surveyor and is often on file with the county or city building office.
Property lines
The parcel outline, parcel number and mapped size come from the Colorado public parcel layer (Governor's Office of Information Technology, from the counties that share their parcels), so a Boulder lot shows the same lines the county assessor draws. Boulder County covers about 464,906 acres of land and 8,995 acres of water.
Mapped lines are approximate. The Boulder County assessor keeps the parcel record (Boulder County website); a licensed surveyor sets the true corners.
Zoning
Boulder County zones its unincorporated land, and Boulder, Longmont, Lafayette each zone the land inside their limits. ParcelSheet shows the use the county assessor lists for the lot and links the county planning office for the district, the uses it allows and the lot size it needs.
ADU and guest houses
Under Colorado's county and city zoning powers (C.R.S. Title 30, Article 28, and Title 31, Article 23), local governments can allow an accessory dwelling unit on a lot with a house. Whether a Boulder lot can add one depends on its district; the county planning office has the rule. ParcelSheet shows the mapped lot size and the ground's slope, the first two things the question turns on.
Septic and soil
ParcelSheet reads the USDA soil survey at the lot: the soil's name, its septic absorption rating and whether it is prime farmland. Boulder County is soil survey area CO643, Boulder County Area, Colorado, last updated September 2026, on Web Soil Survey.
A new or changed septic system in Boulder County needs a permit from the Boulder County local public health agency under CDPHE Regulation 43.
Setbacks
Setbacks in Boulder County come from the zoning district: the front, side and rear distances a house must keep. ParcelSheet does not draw setback lines; the county zoning office gives them for the lot's district, and Boulder, Longmont, Lafayette for land inside their limits.
Hazards that apply
- Wetlands and wildfire. ParcelSheet shows the National Wetlands Inventory near a Boulder lot and the Forest Service wildfire hazard rating at it.
Questions
Is my house in a flood zone in Boulder County?
Type the address in the box above and ParcelSheet reads FEMA's flood zone at the lot's center. FEMA's countywide flood map for Boulder County has 156 panels, the newest effective October 2024. A lender or insurer uses the official FIRM panel; FEMA's Map Service Center has it.
How do I find property lines in Boulder County?
Open the Colorado map, type the address, and the parcel outline from the Boulder County assessor shows on the map with its parcel number and mapped size. Mapped lines are approximate; only a licensed surveyor sets the true corners.
What is my property zoned in Boulder County?
Zoning in Boulder County is set by the county for unincorporated land and by each city (such as Boulder, Longmont) inside its own limits. ParcelSheet shows the use code the county assessor lists and links the office that sets the zoning; the planning office has the final word.
Can I build an ADU in Boulder County?
Under Colorado's county and city zoning powers (C.R.S. Title 30, Article 28, and Title 31, Article 23), counties and cities can allow an accessory dwelling unit, and each sets its own rules. In Boulder County ask the zoning office for the lot's district first; ParcelSheet shows the lot size as mapped so you can see the room you have.
Do I need a septic permit in Boulder County?
Yes. A new or changed septic system in Boulder County needs a permit from the Boulder County local public health agency under CDPHE Regulation 43. ParcelSheet shows the USDA soil survey's septic rating at the lot, from survey area CO643 (Boulder County Area, Colorado).
What can I build on 5 acres in Boulder County?
Zoning in Boulder County is set by the county for unincorporated land and each city inside its own limits (such as Boulder, Longmont). The zoning district decides the uses, how many homes and the smallest lot it allows on 5 acres. ParcelSheet shows the lot size as mapped and the use code on the parcel record; the planning office has the district and its rules. See the Boulder County website.
What are the residential setbacks in Boulder County (2026)?
Setbacks in Boulder County come from the zoning code of the county, or of the city when the lot is inside city limits: the front, side and rear distances depend on the lot's district. ParcelSheet does not draw setback lines or give a number it did not read; the zoning office gives them for the district. See the Boulder County website.
Next to Boulder County: Broomfield County, Gilpin County, Grand County, Jefferson County, Larimer County, Weld County.
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