Building a barndominium or barn in Kendall County: permitting and site work

Kendall County does not enforce a general building code in the unincorporated county. Instead it runs a development-permit process that covers septic, rural addressing and access, floodplain, and subdivision platting. The City of Boerne runs its own building permits inside the city; in its extraterritorial jurisdiction it applies subdivision, platting, stormwater, floodplain and environmental rules, not building permits. For most rural Kendall County projects, the septic permit and the development permit are the steps that matter, not a building inspection.

The on-site sewage facility permit, the septic permit, is usually the binding approval for a rural Hill Country build. In Kendall County it runs through the Kendall County Environmental Health. Located on East San Antonio Avenue in Boerne. Confirm the current phone, email, and the development-permit checklist on the county Onsite Sewage page. Ignore any out-of-state phone result: Kendall County, Illinois shares the name.

Local detail: Kendall County Environmental Health is the local OSSF authority. The septic permit is part of the county development-permit process, so it is usually handled alongside addressing and access. If your parcel is in the southeast of the county near Boerne, read the Edwards Aquifer note below before you design, because the rules can change for those specific parcels.

Visit the official Kendall County page to confirm current forms, fees, and contacts.

The statewide 10-acre exemption does not apply in Kendall County. Section 5.5.C.9.b.iii of the county Development Rules (Development Regulations of November 14, 2022), under the heading for tracts greater than ten acres, says: "A permit shall be required for all On-Site Sewage Facilities within Kendall County's area of jurisdiction regardless of acreage." So a new home on 20 or 200 acres still needs a septic permit before construction starts. The county fee schedule effective September 1, 2023 lists the permit at $300 for a system under 500 gallons a day and $600 at 500 or more. On karst limestone the design usually lands on an aerobic treatment unit. Read at the county's own rules, October 16, 2026; confirm the current requirements with the county before you design.

The TCEQ Edwards Aquifer rule does not reach Kendall County. 30 TAC Chapter 213 was read in full on September 16, 2026: Sec. 213.3(8) defines the Edwards Aquifer across Kinney, Uvalde, Medina, Bexar, Comal, Hays, Travis and Williamson Counties, Sec. 213.22(2) lists those same eight counties for the contributing zone maps, both subchapter titles name them, and TCEQ's application fee form has no Kendall County box. Kendall is named nowhere in the chapter. So a building project here files no Water Pollution Abatement Plan and no Contributing Zone Plan, and carries none of the TCEQ review those add in Comal County next door. Two honest limits. The regulated zones are whatever TCEQ's official maps show, so if your tract sits toward the Comal County line, check the TCEQ Edwards map viewer for your exact parcel. And this is an absence in that one rule, not a finding that Kendall County groundwater is unregulated: your septic design, the groundwater district and the county's own development rules still apply.

The Hill Country sits in the roughly 105 to 115 mph design wind speed band (3-second gust, Risk Category II) under ASCE 7-16, the standard most Texas building codes reference. Most parcels fall between mapped contours, so a designer pulls the exact value for your address from the ASCE Hazard Tool. The local twist is the topographic factor, Kzt: an exposed ridge, hilltop, or escarpment raises the effective wind pressure on a building, sometimes by half again versus flat open ground. A metal or post-frame building on a Hill Country ridge should be engineered for that, which is one reason a sealed design from the builder matters here.

Boerne and Comfort sit on Hill Country limestone, so wells can be deep and water planning matters. Confirm groundwater district registration for any new well, and remember that a well budget and a septic budget both belong in your numbers from the start.

A 1-d-1 open-space valuation from the Kendall Appraisal District lowers the tax valuation on qualifying land, not on buildings. A barn, shop, or barndominium is appraised separately at market value. There is no county square-footage threshold that makes a building permit-free, and ag valuation does not remove the septic or development permit. Ask the appraisal district directly about any structure tied to a qualifying ag operation.