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

Like most Texas counties, Gillespie County does not adopt or enforce a general building code or run building inspections in the unincorporated county. Counties have only the limited authority granted by state law, and a countywide residential building code is not part of it. Inside the City of Fredericksburg, city building permits apply. In the one-mile extraterritorial jurisdiction the city enforces its Subdivision Ordinance and Sign Regulations, by its own FAQ, not its building codes. Out in the county, the touchpoints that actually gate a project are the on-site sewage facility (septic) permit, the County Engineering Department's development review (with a floodplain permit where the land is in or near a mapped flood zone), and a right-of-way permit for a driveway onto a county road.

The on-site sewage facility permit, the septic permit, is usually the binding approval for a rural Hill Country build. In Gillespie County it runs through the Gillespie County Sanitation (On-Site Sewage Facilities) Department. Located at the courthouse complex on West Main Street in Fredericksburg. Confirm the current phone, email, and submittal checklist on the county Sanitation Office page before you file.

Local detail: Important Gillespie-specific rule: the county requires approved wastewater disposal in all areas, regardless of tract size. That means the statewide 10-acre OSSF exemption does not give you a pass here the way it can in neighboring counties. Plan on a permitted system, and on most Hill Country sites that means an aerobic treatment unit because the limestone and thin soils rarely support a conventional drain field.

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

Statewide, 30 TAC 285.3 exempts a single-family home on 10 or more acres from the septic permit if every part of the system is at least 100 feet from the property lines, the effluent stays on the same tract, it is the only dwelling on the tract, and the system is not causing a nuisance or polluting groundwater. In Gillespie County, treat that exemption as effectively unavailable: the county requires approved wastewater disposal across all areas regardless of acreage. Even where a tract would qualify statewide, you are still subject to the construction and groundwater-protection standards in Chapter 285, so design the system properly either way.

Gillespie County is not in TCEQ's regulated Edwards Aquifer Protection Program, so a barndominium here does not trigger the Water Pollution Abatement Plan review that applies over in the San Antonio and Austin recharge counties. You may still see the name "Edwards" locally because the limestone here is part of the Edwards Group geology and a local water unit carries the name, but that is geology and water supply, not the regulated recharge zone. No WPAP filing is required for a typical building project in this county.

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.

Wells in Gillespie County fall under the Hill Country Underground Water Conservation District. If your plan depends on a new well, factor in district registration and the real possibility of a deep, expensive drill through limestone. That well cost belongs in your budget next to the septic system.

A 1-d-1 open-space (ag) valuation from the Gillespie Central Appraisal District lowers the property-tax valuation on qualifying land. It applies to the land, not to your buildings: a barn, shop, or barndominium is appraised separately at market value. There is no county square-footage threshold that makes a building "exempt" from permitting, and an ag valuation does not remove the septic permit requirement. If a building genuinely supports a qualifying ag operation, talk to the appraisal district about how it is treated, but do not assume a barn is permit-free because the land is ag-valued.

Outside the city, any split of a tract falls under Gillespie County's Subdivision and Manufactured Home Rental Community Regulations, adopted December 19, 2022 and amended December 23, 2024, run by the County Engineering Department. Since the 2024 amendment, where each lot will rely on its own well, no lot may be smaller than six acres, and the number of lots cannot exceed the parent tract's acreage divided by eight. The county's own examples put it plainly: a 15-acre tract cannot be split at all, and 30 acres yields three lots at most. Lots on a community or public water system with a septic system drop to two acres (acreage divided by three), and lots with both public water and public sewer to one acre (acreage divided by two).

Each lot needs 200 feet of frontage on a county road, a state or federal highway or another public road, or 100 feet on a cul-de-sac, and the plat draws a 20-foot building line on the front, sides and rear. Because the county sits inside the Hill Country Priority Groundwater Management Area, a plat served by wells also carries a certification from the general manager of the water district that it meets the district's rules; the well rules themselves are on the Fredericksburg page. Roads shown on a plat are not accepted for county maintenance, so the lot owners keep them up. The plat fee schedule charges $500 plus $100 a lot for a plat of one to four lots, the same for a replat, $100 a lot for an amending plat, and the actual cost of any outside engineering review.

One rule catches rental plans rather than homes. Two or more spaces rented out for manufactured homes, a category the county reads to cover RVs, tiny homes and shipping containers, make a Manufactured Home Rental Community, which needs the County Engineer's approval before any work starts. A small ranch setup can ask for a waiver: fewer than one unit per acre, no more than eight units, every unit at least 40 feet from the property lines and none in the 100-year floodplain.

Beyond the state exceptions in Local Government Code 232.0015 (every piece over 10 acres, land kept in farm, ranch, wildlife or timber use, and certain family divisions), Section 4.2 of the county rules adds four of its own: a division made by a court judgment or in probate; a division among heirs or gift-deed donees related within the third degree, where each resulting tract still meets the lot rules; a sale or swap with the adjoining owner, now only where the smaller tract is at least six acres and the resulting tracts average eight; and a piece surveyed out only to get a loan on it. None of them may move a line between platted lots or shrink a platted subdivision.

Each exception is claimed on a notarized affidavit that names the deed and attaches the field notes and survey. The limits ride with the land: a family lot later sold to someone outside the family, a loan tract that is conveyed, or a farm tract that stops being farmed needs a plat first, and the requirement has to be written on the survey and in every deed. The affidavit also says the lot must still meet the county's lot size, access spacing, septic and well rules. The right-of-way rules close the loop: the county will not issue a driveway permit on a tract that should have been platted and was not.

Any work inside the right-of-way of a county-maintained road, a new drive, a culvert, a non-standard mailbox, even boulders, needs a permit under the county's Right-of-Way Regulations (in effect May 28, 2024, last amended June 15, 2026). A single-family drive costs $50, and starting before approval doubles it. The process opens with a pre-application meeting with the County Engineer; the office says within 10 business days whether the file is complete and then reviews it within another 10, and an approved permit lapses after six months without progress. Section 3.01 spaces a new drive 200 feet from the nearest state road intersection, 100 feet from any other road or drive, and 50 feet from a property or easement line, and it must meet the road at an angle between 80 and 100 degrees.

A house drive may be up to 24 feet wide with a 5 to 20 foot radius, all of it inside your own frontage. Where it crosses a road ditch it needs a culvert of at least 18 inches (or a 2 by 2 foot box) with 12 inches of cover, sized to carry 125 percent of the five-year storm flow, with sloped concrete ends. Clearing or grading of one acre or more adds a rock construction entrance at least 50 feet long and 12 to 26 feet wide, of 4 to 8 inch washed stone laid 8 inches deep. Fences are not allowed in the right-of-way, a gate across a public right-of-way must stay unlocked, and any such gate must be at least 10 feet wide.

The address comes after the access. The county's 911 request form requires an approved right-of-way permit (or an approved location for a drive to be built later) before the Rural 9-1-1 Addressing office assigns a number, measured within 35 feet of the center of the drive; a drive off a state highway needs TxDOT's permit from its Fredericksburg office instead, which carries no fee. A private lane serving two or more habitable buildings, cabins, a shop office or a wedding hall included, must be named, with a separate number for each building. The blue reflective number sign is $15 at the courthouse, cash or check.

The Engineering Department asks for a Development Determination Form before any development of a property, including new construction, grading and paving. It costs nothing: you send a site plan and a short narrative, and the floodplain administrator checks whether any part of the land is in a mapped flood zone, whether the work sits within 100 feet of one, and whether impervious cover reaches 40 percent, then returns the form either clearing the project or listing the permits it needs. Any change to the site plan voids the answer.

The county's Flood Damage Prevention Ordinance, effective July 28, 2025, reaches past the 2001 FEMA maps: it adopts FEMA's newer Base Level Engineering mapping, treating the 1 percent flood extent as Zone A and the 10 percent extent as floodway. Inside a mapped flood zone, a new home's lowest floor (basement included) has to clear the base flood level by a foot or more; just outside one, in Zone X but within 100 feet of it, the owner files an elevation certificate proving the ground next to the house is higher than that level. A tract in Zone X developed to 40 percent impervious cover or more must hold its runoff to the old peak flows. The development permit application carries a $100 administrative fee plus the cost of any third-party review (both doubled if work began first), and the permit expires after a year without progress.

On the septic side, the septic fee sheet effective October 14, 2025 charges $325 for a new system under 500 gallons a day, $425 where it needs a maintenance contract (as aerobic systems do), $550 and $750 for systems of 500 gallons a day or more, $200 to repair or alter one, and $150 for a reinspection, plus a $10 state fee on every permit. The county septic order adopted the same day also takes servicing out of the owner's hands: an aerobic system must be maintained by a TCEQ-registered technician or licensed provider, not the homeowner, and each report has to record the sludge level in the pump tank and the condition of the spray area.

The county does not publish this, so we asked for it. Under the Texas Public Information Act the Sanitation Office sent its export of every septic Authorization to Construct from January 1, 2023 to October 28, 2026: 1,030 in all. Full years ran 332 in 2023, 289 in 2024 and 232 in 2025. Comparing the same January 1 to October 28 window each year, the count went 276, 241, 196, then 177 in 2026, about 36 percent below 2023. About four in 10 were aerobic systems, the kind the county requires a maintenance contract for. The export does not separate new homes from repairs. The year-by-year table is in the Hill Country septic guide.