Building permits, zoning and septic rules in Caldwell County, Texas

Unincorporated Caldwell County, Texas requires a Residential Construction Permit for a new residential structure, an addition that increases bathroom or bedroom count, or major rebuilding after fire or flood¹. The published residential permit fee is $225, and starting work before approval doubles the applicable fee⁵. Caldwell County exempts enclosing a staircase or porch, a carport for fewer than 10 cars, a deck, roof replacement, exterior-facade remodeling and sidewalk construction¹. The permit remains valid for 2 years or until construction is complete¹. An application needs land and ownership records, current tax certificates, and a site sketch that identifies the proposed work, access, property lines, floodplain, easements, wells and septic components¹.

Caldwell County Sanitation/Development Services handles residential and commercial site construction permits, septic permits and inspections, subdivision and development review, floodplain management, platting and code enforcement⁴. The office is at 1700 FM 2720, Lockhart, TX 78644, and its phone number is (512) 398-1803⁴. Call for an appointment before submitting a project⁴. Caldwell County publishes applications for residential construction, septic, subdivision, floodplain, construction and variance requests, along with its development fee schedule⁴. A parcel split or subdivision adds another layer: Commissioners Court approval is required before a subdivision or resubdivision plat can be recorded, and projects in a municipality's ETJ may also require submission to that municipality¹⁰. After you submit a construction application, the County Engineer reviews it, and a noncompliant first submittal is returned with comments within 10 calendar days; applicants are expected to respond within 7 calendar days, and an application can be deemed withdrawn after 10 days without a response¹⁰.

Unincorporated Caldwell County has no countywide zoning or general county land-use zoning power². At the county level, that means no zoning rule sets minimum dwelling size, minimum lot size, setbacks, lot coverage or building height⁷. Parcel-specific rules can still come from a city or a special-purpose district; airport zoning administered by the City of San Marcos may affect development within its hazard area in Caldwell County³. No countywide zoning does not mean no permits: residential construction, septic, floodplain work, subdivisions and county-road access remain regulated through other county processes^1,6,10. Before relying on the countywide answer, ask Sanitation/Development Services whether the parcel lies in a municipal ETJ, airport hazard area or another special jurisdiction^3,4.

Caldwell County Sanitation/Development Services issues OSSF permits and requires a site evaluation to determine soil suitability and the system type^4,6. The regular single-family conventional-system fee is $400, the engineered-system fee is $450, and an approved permit is valid for 1 year and is non-refundable⁶. A complete design receives a 5-day review if no design changes are needed⁴. Type 1a soil, floodplain sites and subdivisions restricted to engineered systems require design by an engineer or registered sanitarian⁶. Installation requires advance notice for an inspection and an installer or installer apprentice must be present; successful inspection leads to the permit to operate⁶. Texas's 10-acre exemption may apply only when every state condition is met, including one home, a qualifying site evaluation and at least 100 feet between every system component and a property line¹². Tank replacement carries a $100 fee and reworking existing drain fields a $200 fee⁶. Septic and site-construction applications may be processed at the same time¹⁰.

Caldwell County has no county zoning restriction on RV occupancy, temporary camping, tiny-home occupancy or manufactured-home occupancy in unincorporated areas⁷. A separate permit rule still matters: the Development Ordinance defines a residential structure to include a manufactured home or recreational vehicle used to house a family, so an RV used as housing falls within the Residential Construction Permit framework¹. A tiny home used as a dwelling also fits the county's general permit requirement for construction or installation of a residential structure¹. Mobile homes must be tied down or anchored and have a closed-in foundation¹. Ask Sanitation/Development Services how the office will classify the exact unit and setup before delivery, especially if the plan is temporary occupancy during construction⁴. Municipal or airport-area rules may differ on affected parcels³.

1. Call Caldwell County Sanitation/Development Services at (512) 398-1803 to identify the residential, septic, floodplain, subdivision and access approvals for the parcel⁴.
2. Confirm whether municipal, ETJ or airport-area rules add another review^3,10.
3. Assemble the property description, ownership record, current tax certificates and site sketch required for the residential application¹.
4. Document potable water with a utility receipt or bill, a private-well driller's log, or an engineered or certified rainwater system⁹.
5. Complete the septic site evaluation and secure the county OSSF permit before installation⁶.
6. Apply for county driveway approval when work touches a county right-of-way; a new or materially changed driveway must be accompanied by a driveway permit application with the site permit, and the listed driveway right-of-way permit fee is $50¹⁰.
7. Use TxDOT's Form 1058 instead when access connects to a state highway¹¹.
8. Obtain the residential permit before work begins to avoid doubled fees⁵.

Ask Sanitation/Development Services whether the parcel is in or within 300 feet of a floodplain, because that changes floor-elevation and permit documentation requirements¹. Only 3.8% of Caldwell County soils are rated without severe limitations for a conventional drain field, so get the septic site evaluation before fixing the house site or purchase budget^6,13. If any FEMA floodplain lies within the construction area, a floodplain permit or LOMR/CLOMR is needed, the listed floodplain permit or revision fee is $750 plus consultant reimbursement, and a floodplain setback of up to 25 feet beyond the 100-year floodplain can apply⁹. Confirm access too: county right-of-way work needs a county permit, while a state-highway connection follows TxDOT's separate process^10,11. If land will be divided, verify plat approval and whether ETJ review applies before closing¹⁰. Finally, identify the potable-water plan; the residential application accepts utility documentation, a private-well driller's log, or an engineered or certified rainwater system, but we could not confirm the separate water-well permitting authority⁹.