Castle Rock, CO Zoning, Building Permits & Septic Rules

The Town of Castle Rock, Colorado runs its own zoning under Title 17 of the town code¹ and adopts its own building codes². Inside town limits a separate septic system is allowed only when Town Council authorizes it after finding extraordinary hardship³, and a parked RV may not be lived in⁴. Land outside town limits in Douglas County follows the county's rules instead⁵.

At a glance

Zoning: Town of Castle Rock zoning (Title 17) with R-1, R-2, MH and PD districts¹
Building permit: Town building permit required for accessory dwelling construction; town adopts its own building codes⁶²
Septic: New separate septic only with Town Council approval after a hardship finding; health department approval also required³
Wells: Individual or separate water systems not permitted; town water required⁷
RV living: Not allowed in a parked recreational vehicle⁴
Accessory dwelling: Allowed, one per lot, owner must live in the main home⁸
Minimum lot, R-1: 9,000 square feet⁹
Front setback, R-1 and R-2: 25 feet¹⁰¹¹

Who to call

Building permits

Town of Castle Rock Development Services Building Division

Building permits inside Castle Rock town limits, applied for through the town's eTRAKiT portal

720-733-3527

100 N. Wilcox St.

Septic permits

Douglas County Health Department

On-site wastewater (septic) permits in Douglas County; also the office to confirm septic approvals for a Castle Rock address

720-643-2400

11045 E Lansing Circle, Third Floor, Englewood, CO 80112

Contact details are copied from each office’s official page and were checked against it on October 16, 2026.

Off-grid gear

Going off-grid in Town of Castle Rock means bringing your own water and power. The kit we’d start with:

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Does Castle Rock, Colorado have zoning, and what does it mean for RVs, tiny homes and setbacks?

Yes. The Town of Castle Rock administers its own Title 17 zoning code with R-1, R-2, MH and PD districts¹. Zoning rules are set district by district, so check your lot's district first.

In the R-1 single-family district, the minimum lot area is 9,000 square feet⁹, the minimum front yard is 25 feet¹⁰, and principal buildings top out at 35 feet while accessory buildings top out at 20 feet¹². In R-2, the minimum lot for a single-family dwelling is 6,000 square feet¹³, the front yard is also 25 feet¹¹, and the same 35-foot and 20-foot height limits apply¹⁴.

Inside Castle Rock, a manufactured home may be occupied only on a space within a manufactured home park¹⁵. We could not confirm a tiny-home rule for Castle Rock; ask the Development Services Building Division before buying.

Do you need a building permit in Castle Rock, and who issues it?

Yes. The Town of Castle Rock issues building permits inside town limits, and the town code requires one for all construction of accessory dwelling units⁶. The town adopts and amends the International Building, Residential, Plumbing, Mechanical, Energy Conservation and Fire codes, among others².

Applications go through the town's eTRAKiT portal, and the Building Division takes questions at 720-733-3527¹⁶. A homeowner may pull a permit only for work on their own primary residence¹⁶.

Douglas County's Building Division only covers unincorporated land. If your parcel lies outside town limits, see the Douglas County page for that office's rules.

How do septic permits and wells work inside Castle Rock?

Castle Rock expects you to connect to municipal sewer and water. The town code says no individual residence or other development may create a separate septic system unless Town Council authorizes it with a final subdivision plat after finding that connecting to the municipal wastewater system would create an extraordinary hardship³. Individual or separate water systems are not permitted at all, so a private well is not an option inside town limits⁷.

If a town water or sewer line comes within 400 feet of an existing separate system, the owner must connect within 180 days of the town's notice, at the owner's expense¹⁷.

Where a septic system is approved, the Douglas County Health Department permits septic systems in all areas of the county¹⁸¹⁹. The town code itself names both Tri-County Health Department and Douglas County Health Department, so confirm which agency applies to your address before relying on either²⁰. A certificate of occupancy is withheld until the health approvals are in hand²¹.

Can you live in an RV, camper or accessory dwelling in Castle Rock?

No RV living. Castle Rock allows an RV to be parked on a residential lot but not used for living or housekeeping⁴. Camping in tents or shelters on parks, open space and public property is unlawful unless the area is designated or the town issues a written permit²²; the town code summary we reviewed does not address camping on private land.

An accessory dwelling unit is the legal way to add a second home on a lot. Castle Rock allows one per lot, requires the owner to live in the primary dwelling, and bars RVs and mobile homes from serving as ADUs⁸. A detached ADU is capped at an 800 square foot footprint unless PD zoning is more permissive⁸.

Building a home in Castle Rock: the steps, in order

Confirm the lot is inside town limits and find its zoning district¹.
Check the district's lot size, setbacks and height limits, such as 25-foot front yards in R-1 and R-2¹⁰¹¹.
Plan for town sewer and water, because separate septic and wells are not allowed without Council approval³⁷.
Apply for the building permit through the town's eTRAKiT portal; call the Building Division at 720-733-3527 with questions¹⁶.
If a septic exception applies, get health department approval before occupancy²¹.
We could not confirm the town's inspection sequence; ask the Building Division.

What stays with Douglas County, and what should you check before you buy?

Castle Rock's rules stop at the town line. In unincorporated Douglas County, the county requires building permits for new residential construction²³ and enforces its own zoning resolution⁵; see the Douglas County page for details.

For Douglas County as a whole, the median property tax bill is $3,707 a year²⁴ and the typical home value is $711,894²⁵. Annual precipitation is about 18.5 inches²⁶. These are county figures, not Castle Rock-only numbers.

We could not confirm Castle Rock's rules on floodplain development, driveway access, lot coverage, owner-builder permits beyond the homeowner rule above, or short-term rentals; ask the Building Division before you buy.

Watch-outs

Castle Rock does not allow private wells; town water is required⁷.
A separate septic system needs Town Council authorization and a hardship finding, and the system must later be abandoned under a Council resolution³.
A parked RV cannot be used for living or housekeeping on a residential lot⁴.
The town code names two different health agencies for septic, so confirm which applies with the Douglas County Health Department²⁰¹⁹.

Sources

Written October 16, 2026 from the rules quoted below, each taken from an official source and re-checked by an independent reviewer. This is research, not legal advice: rules change, so confirm with the office before you buy or build.

Unanswered questions are usually a sign that Town of Castle Rock publishes no rule on the point, not that none exists. Douglas County’s page lists the county offices to call.

Building permits, zoning and septic rules in Castle Rock, Colorado