Building permits, zoning and land rules in Costilla County, Colorado

All new structures in any zone district in unincorporated Costilla County require a county building permit, and an OWTS permit and water source must be in place before an occupancy permit is issued¹. Unsewered structures also need local public health agency OWTS approval before building approval⁴. Inside San Luis, the town issues building permits for single-family and multi-family dwellings after approving a plot plan; OWTS approval remains with the local public health agency^4,5. Costilla County has adopted the 2018 International Residential Code as its building code, along with its own design criteria: a countywide snow load of 30 pounds per square foot and a wind load of 115 miles per hour². Permits here don't last forever: construction permits must be renewed annually, and the Land Use Administrator has discretion to issue up to 3 annual permits for a property, with a 4th permit requiring a variance request to the Board of County Commissioners². Manufactured homes face their own age rule, stated plainly on the county's page: manufactured homes must be 1976 or newer to be allowed in Costilla County². Colorado's own framework explains why the county sets these rules itself: the state is a "local control" state, so decisions like building-code adoption are made by the county rather than through a uniform statewide code¹⁰.

The Costilla County Planning and Zoning Department is the office for building permits, zoning permits, physical addressing, and OWTS soil evaluations, located at 400 Gaspar Street, San Luis, Colorado 81152². Reach the office at (719) 937-7668; it is open 7:00 a.m. to 5:30 p.m., Monday through Thursday, with no closure for lunch². Building inspections are scheduled by calling the Planning and Zoning Office at that same number². The department asks buyers to contact it before purchasing land or starting a land-use activity in Costilla County². For a physical address, bring the parcel's legal description and the owner's name as registered with the Costilla County Assessor; the fee is $20, and the county does not issue a physical address to vacant land².

The county's Land Use Code establishes zoning districts in unincorporated Costilla County, including Agricultural (A) and Estate Residential (ER), each with its own minimum lot size². Colorado law gives counties authority to zone unincorporated territory, regulating building location, height, bulk, lot size, lot coverage, open space, population density, and land use by district¹¹. Building height and story limits in Colorado are set at the local level rather than by a statewide number, so the applicable local zoning ordinance controls what you can build on a given lot¹². One state rule matters if you're buying a larger tract with an eye toward splitting it later: a division of land into parcels of at least 35 acres each, none intended for use by multiple owners, is excluded from Colorado's subdivision definition⁸. Confirm the zoning district and minimum lot size for your specific parcel with the Planning and Zoning Department before you buy². Inside San Luis, town zoning governs uses and structures; OWTS approval still comes from the local public health agency^4,6.

Costilla County Planning and Zoning issues OWTS (septic) permits for systems with a design capacity of 2,000 gallons per day or less, using the county application under Colorado Regulation 43³. Before installing, altering or repairing an OWTS, obtain local public health agency approval and submit property, site-and-soil and system-design information⁴. For unsewered structures, OWTS permit and inspection approval are prerequisites to building or occupancy approval, so resolve septic early with Planning and Zoning^3,4. Systems above 2,000 gallons per day also face state site-location, design-approval and discharge-permit requirements⁴. A final inspection is required before a permitted system goes into use¹³. Local septic fees are capped at agency costs, with a $23 state surcharge for each new, repaired or upgraded system permit⁴. Colorado prohibits new cesspools and requires adequate sewage disposal for occupied structures without sewer service¹³. About 34.6% of Costilla County soils are rated not limited for conventional drain fields; that countywide rating does not replace a parcel-specific site evaluation^4,9.

We could not confirm a Costilla County rule for living in an RV on a residential parcel; ask the Planning and Zoning Department before buying land for that purpose². Colorado-regulated tiny homes can be approved for long-term living, but plans must go to the Colorado Division of Housing before construction, the home must meet applicable codes and local zoning, and certification applies to the installation site¹⁴. Costilla County separately says temporary cargo and shipping containers are allowed only during construction². Manufactured homes have a clearer local rule: Costilla County requires them to be 1976 or newer, while Colorado allows a HUD-code home to be installed where local zoning permits it^2,14. Acting as your own builder does not create a general exemption from new-home rules: the confirmed state exemption covers repair or maintenance on your own property, not construction of a new residence⁷.

1. Contact Costilla County Planning and Zoning at (719) 937-7668 before purchasing land or starting a land-use activity².
2. Confirm the parcel's zoning district and minimum lot size; inside San Luis, use the town's zoning and plot-plan approval process for residential building permits^2,5,6.
3. For an unsewered home, resolve the site-and-soil evaluation and OWTS approval before building approval with the local public health agency; Costilla County Planning and Zoning handles county OWTS applications^3,4.
4. If you need a well, apply to Colorado's Division of Water Resources; complete applications can take up to 49 days to review, and an augmentation plan may be needed¹⁵.
5. Apply for the county building permit using the adopted 2018 IRC and county design criteria, and renew construction permits annually².
6. For direct state-highway access, apply to CDOT; a Level 1 single-family residential or agricultural access permit costs $50¹⁶.
7. Arrange final OWTS inspection before using the system, and have the OWTS permit and water source in place before county occupancy approval^1,13.

Before buying Costilla County land, confirm a usable water source with Colorado's Division of Water Resources: new groundwater-diverting wells require a permit, subject to statutory exemptions and basin-specific rules, and an augmentation plan may be needed¹⁵. A tract divided into parcels of at least 35 acres each, none intended for multiple owners, is excluded from Colorado's subdivision definition; that exemption does not establish the parcel's zoning district or minimum lot size^2,8. Ask Planning and Zoning about the parcel before purchasing². About 34.6% of county soils are rated not limited for conventional drain fields, but an OWTS application still requires site-and-soil information^4,9. Costilla County averages about 17.5 inches of annual precipitation, with severe drought in about 34.2% of years⁹. The effective property tax rate is about 0.3%, with a median annual bill near $531 and a typical home value around $184,317⁹.