Open rolling Blackland Prairie cropland grading into a post oak belt of the Eastern Cross Timbers, with a pecan-lined creek.
Williamson County No county building code

Barndominium Builders in Williamson County, TX

Williamson County has no residential building code, and the county says so in its own words: it has never adopted an order applying Subchapter F of Local Government Code chapter 233. There is no county building permit, no county fee and no county inspector for a house. What the county does require is a Certificate of Compliance on every structure outside the floodplain, a septic permit on a tract of any size, and a platting answer before either of those. The ground splits at the Balcones Escarpment. West of I-35, toward Liberty Hill, Leander and Georgetown, it is limestone, thin soil over rock and the Edwards Aquifer recharge zone, where TCEQ has a say the county does not. East toward Taylor, Granger and Coupland it is Blackland Prairie clay, and the county's own pavement tables run the plasticity index to 55. Two grounds, one county, and the acreage sits at both ends.

Williamson County at a glance

County
Williamson County
Population
752,827
Where we build
Georgetown, Round Rock, Bell County, Burnet County

ZIPs 78626, 78628, 78633, 78641, 78642, 78613, 78664, 78665 and more

Site visits
We meet you on the tract, Georgetown or anywhere else in Williamson County
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Building conditions in Williamson County

What actually changes from one Texas jurisdiction to the next: who issues the permit, whether the residential code is enforced there at all, what the structure has to be engineered to, and what the ground is like. These are the numbers your drawings have to satisfy.

Build conditions for Williamson County , Texas . BUILD CONDITIONS WILLIAMSON COUNTY…Williamson CountyNO COUNTY BUILDING…ADOPTED RESIDENTIAL CODENO COUNTY BUILDING…This jurisdiction publishes no design wind speed. It is settled in writing with the authority overyour parcel before the frame is ordered.ZONING · NONE — A TEXAS COUNTY CANNOT ZONE, A…Two acres on a private well, one acr…The county's own development FAQ reads: there are no zoningregulations in Williamson County, and if you are inside the city…IMPACT AND PERMIT FEESCounty-published permit and review f…Williamson County charges nothing for a building permit because itissues none. What it does publish, on the County Engineer's on-site…WHO ISSUES THE PERMITWilliamson County Department of Infr…3151 SE Inner Loop, Suite B, Georgetown, TX 78626. Main line512-943-3330, fax 512-943-3335, septic email ossf@wilcotx.gov.…
Build conditions for Williamson County, drawn from the sourced facts on this page. Every figure above is cited in the quick-facts panel below, with its source and vintage.
The county publishes its own answer: no building code at all
Filed under a question about certificates of occupancy, Williamson County's development FAQ says it outright: "Williamson County has not adopted a resolution or order requiring the application of Subchapter F, 'Residential Building Code Standards Applicable to Unincorporated Areas of Certain Counties', as found in Section 233 of the Local Government Code. Therefore, Williamson County does not require any new residential construction to conform to any building code." The same answer adds that the county has no authority to zone property for land use and no authority to issue a certificate of occupancy. Search the county's own site for "Subchapter F" and that FAQ is the first thing it returns; there is no adopting resolution behind it. No permit, no plan review, no county inspector, and no design wind speed published for the unincorporated county.

Williamson County, Infrastructure — Developers FAQ, "Does Williamson County issue a certificate of occupancy?", dated 25 October 2023 — wilcotx.gov/faq.aspx?TID=73

Every structure needs a Certificate of Compliance — even outside the floodplain
Article 3 Section C of the county's Flood Damage Prevention Order: "A Floodplain Development Permit shall be required ... for all areas of special flood hazard. A permit shall not be required for property determined to be clearly outside the areas of special flood hazard, but a certificate reflecting that determination shall be required." Section A puts the reach beyond doubt — the requirement to seek a determination applies to all other land within the jurisdiction of Williamson County. The county states the practical rule on its Floodplain Management page: a Certificate of Compliance is required for all structures or other developments outside a floodplain in the unincorporated areas. Skipping it is specifically declared a violation at Article 6 Section G(1)(b), a misdemeanor carrying a fine of up to $500 for each violation with each day a separate offence. It is not a code review: no plans are examined and no inspector looks at the building.

Williamson County Flood Damage Prevention Order, Articles 3 and 6 — wilcotx.gov/DocumentCenter/View/3244; Williamson County Floodplain Management — wilcotx.gov/652/Floodplain-Management

Whether the shop counts against your drainfield turns on three words
Section 10(E)(10) of the county's septic order excludes a workshop from the wastewater flow calculation only if it clears all three tests at once: "A climate controlled structure, which is separated from the main residence, does not have plumbing and is used for storage, exercise space, as a workshop, office space, music space, artistic space, animal sheltering or similar is not considered a part of the single family living space structure for the purpose of wastewater flow design calculations." Attach the shop to the house, or put a sink in it, and it is back in the calculation. Section 10(A)(3) goes further: a structure with either a bathtub or shower and a kitchen is a living unit, and "Independent living units, both attached or detached, will be classified as separate residences for design and density calculations." A shop apartment is not extra square footage here. It is a second residence.

Order Adopting Rules of Williamson County, Texas for On-Site Sewage Facilities, adopted 12 January 2021, sections 10(A)(3) and 10(E)(10) — wilcotx.gov/DocumentCenter/View/3109

Two acres on a well, one on a public supply — double the state floors
Section 10(D)(2) of the county's septic order: "For properties where each lot maintains an individual water supply or is otherwise not served by a public water supply, each lot shall contain at least two (2) acres in surface area," and one acre where the lot is on a public supply. The state minimums at 30 TAC 285.4(a)(1) are one acre and half an acre, so Williamson has doubled both. Subsection (c) then takes land back out of the count: "recognizable bed and banks of wet weather creeks, bodies of water and dedicated public road easements shall be excluded from the overall square footage of the lot." On the limestone side of the county a dry drainage is exactly what a wet weather creek is, so a two-acre deed can be a sub-two-acre lot for septic purposes. Appendix F1 of the subdivision regulations repeats the exclusion in the same words.

Williamson County On-Site Sewage Facilities Order, section 10(D)(2) — wilcotx.gov/DocumentCenter/View/3109; Williamson County Subdivision Regulations, 4 March 2025, Appendix F1 — wilcotx.gov/DocumentCenter/View/15640

On the Edwards recharge zone the number is twenty per cent impervious cover
Williamson is first on TCEQ's list of the eight counties covered by the Edwards Aquifer rules in 30 TAC chapter 213. The exemption written into the rule itself, at 30 TAC 213.5(h)(2), has no acreage limb at all: "An individual land owner who seeks to construct his/her own single-family residence or associated residential structures on the site is exempt from the Edwards Aquifer protection plan application requirements under this section, provided that he/she does not exceed 20% impervious cover on the site." TCEQ's guidance page for private residences adds further routes, including a lot larger than five acres with no more than one single-family residence on it, and counting rainwater harvested from the roof against the total — its worked example takes 37 per cent down to 19. Impervious cover there means "rooftops, driveways, concrete pads, sheds, sidewalks." A metal building, an apron and a caliche drive are exactly that list. Roughly 9,000 square feet of cover is about 21 per cent of one acre and about 10 per cent of two.

30 TAC 213.5(h)(2); TCEQ, Edwards Aquifer: Private Residences, last modified 17 February 2026 — tceq.texas.gov/permitting/eapp/edwards-aquifer-private-residences; TCEQ Edwards Aquifer Protection Program — tceq.texas.gov/permitting/eapp

Ten acres does not exempt you — the order names the number and kills it
Section 10(B) of the county's septic order: "After September 27, 1999, each new or altered single family dwelling, multi-family dwelling, business, commercial, or industrial structure, regardless of the size or acreage of the tract of land on which the dwelling or structure is located, must be connected to an approved On-Site Sewage Facility ('OSSF') or be connected to an authorized wastewater disposal system. Tracts of land that are ten acres or larger are not exempted and must comply with these Rules." TCEQ said the same thing about the state rule when it amended it in 2023, explaining that the old wording "has been misinterpreted by homeowners, installers, authorized agents, and other stakeholders." In Williamson County the belief dies in the county's own text, with the acreage spelled out.

Williamson County On-Site Sewage Facilities Order, section 10(B) — wilcotx.gov/DocumentCenter/View/3109; TCEQ preamble to the 2023 amendment of 30 TAC 285.3(f)(2)

Also worth knowing before you build in Williamson County

A tract divided the wrong way cannot get a septic authorisation
Section 10(D)(3) of the septic order is one sentence long and it can foreclose a build: "A tract that has been subdivided without compliance with the Williamson County Subdivision regulations will be ineligible to obtain an authorization to construct an on-site sewage facility." No septic authorisation means no house. The county's platting exemptions are real but they are paperwork, not silence: Appendix A3.2 of the subdivision regulations requires every exemption to be "approved in writing by the County Engineer prior to the division of the property," supported by an affidavit setting out the detailed basis for the exclusion, subject to penalties of perjury, plus copies of the deeds. Two dates matter. A tract whose boundary has not changed since 21 February 1985 may be sold entire without platting, and a property fronting a public street whose boundary has not changed since 1 February 2000 is a legal lot.

Williamson County On-Site Sewage Facilities Order, section 10(D)(3); Williamson County Subdivision Regulations adopted 4 March 2025, Appendices A2 and A3 — wilcotx.gov/DocumentCenter/View/15640

There is a county fire code, and the appraisal district decides if it reaches you
Williamson County passed the 250,000 population bracket in Local Government Code section 233.061 and adopted the 2018 International Fire Code, which the Fire Marshal's office dates to 10 November 2020. Its scope at section 2.4(A) is unusually worded: it applies to "all public buildings, commercial establishments, and multi-family dwellings with four or more units, as determined by the current property designation identified by the Williamson Central Appraisal District." The county's own FAQ answers more bluntly — all commercial structures in the unincorporated areas. A house you live in is none of those, and section 1.1(B) confirms the fire code "is not intended to be a building code." But the trigger is the appraisal roll, and section 3.7(B) treats "a change in occupancy classification involving a change in the purpose or level of activity in a building, including the renovation of a warehouse into a loft apartment" as a substantial improvement. Anyone planning to let the building should settle its classification with the appraisal district before framing, not after.

Williamson County Fire Code, Second Edition, sections 1.1, 2.4 and 3.7 — wilcotx.gov/DocumentCenter/View/1928; Williamson County Fire Marshal FAQ — wilcotx.gov/faq.aspx?TID=37

Only three per cent of the county's growth went to unincorporated land
Williamson County grew from 615,611 in 2020 to 752,827 in 2025, an increase of 137,216 people. The balance of the county — everyone outside every city limit — went from 189,898 to 194,323, absorbing 4,425 of them, about three per cent. Everything else went into a city. Georgetown grew 55.6 per cent, Hutto 63.9, Leander 52.7, and Liberty Hill 261.9 and Jarrell 228.9 as their limits pushed outward. Cedar Park grew 2.5 per cent and is finished. At the eastern end Granger grew 3.6 per cent, Bartlett 4.2, Florence 4.4, Coupland 5.5 and Thrall 7.7 — the farm towns are static, and that is where the land is quietest.

U.S. Census Bureau Vintage 2025 population estimates, co-est2025-alldata.csv and sub-est2025.csv, computed on POPESTIMATE2020

About 219 people per square mile of unincorporated land
Williamson County covers 1,115.869 square miles of land. Roughly 230 of those, about 21 per cent, sit inside a city limit once the seven cities that straddle a county line are counted only for their Williamson share. That leaves about 886 square miles carrying 194,323 people, or around 219 to the square mile — at typical household size, roughly one house per eight acres. That is not open ranch country and it is not suburbia either. Seventeen city extraterritorial jurisdictions reach across much of it, and the county publishes a map and a contact list because who reviews your plat depends on which one you are standing in.

U.S. Census Bureau 2025 Gazetteer county and place files (GEOID 48491, land area 1,115.869 sq mi) with Vintage 2025 population estimates; Williamson County ETJ Map and Platting Authority Contacts — wilcotx.gov/DocumentCenter/View/3110

No groundwater district permits your well here — and that is not good news
Williamson County has no groundwater conservation district. The county publishes the position itself: "Williamson and Travis counties are surrounded by groundwater conservation districts: Clearwater WCD north of us in Bell County; Post Oak Savannah GCD to the east in Milam County; Central Texas GCD west in Burnet County ... Travis and Williamson counties are islands in the middle of regional water conservation efforts." The same piece notes that most western Williamson wells draw on the Trinity Aquifer, which recharges at only four to five per cent of rainfall, and that the county is oversubscribed to groundwater west of Interstate 35. So nobody spaces, studies or manages the next well drilled next door. A licensed driller and a State of Texas well report are still required, and where a subdivision is supplied by groundwater the county requires a licensed engineer or geoscientist to certify adequate supply under 30 TAC chapter 230.

Williamson County News Flash, "Why the county needs a groundwater conservation district", 16 March 2023 — wilcotx.gov/CivicAlerts.aspx?AID=42; Williamson County Subdivision Regulations sections 4.19 and 5.39

TCEQ can stop your dozer on land with no building permit
On the Edwards recharge or transition zone, TCEQ's rule is that "If you discover any sensitive feature during construction, replacement, or rehabilitation, immediately suspend all regulated activities near it, and notify TCEQ," and that "Neither construction nor soil-disturbing activities may proceed until TCEQ has reviewed and approved the methods proposed to protect the feature." A sensitive feature is a permeable geologic or artificial feature where surface water can reach the aquifer quickly — a cave, a solution cavity, a sinkhole. A Texas-licensed engineer or geoscientist prepares a protection plan and TCEQ has a week to review it; meanwhile no activity should typically occur within fifty feet. The number to call for Williamson County is 512-339-2929. That is a state stop-work power on a parcel where the county issues no building permit at all.

TCEQ, Edwards Aquifer: Sensitive Features Encountered During Construction — tceq.texas.gov/permitting/eapp/sensitive-features-encountered-during-construction; 30 TAC 213.3(29)

The county's own pavement tables describe both halves of the ground
Section B4.4 of the subdivision regulations tells a geotechnical engineer that "Borings shall be to a depth of ten ft or, if solid rock is encountered, one ft below non-fractured rock or 3 ft below fractured rock," and that the soils report must carry the subgrade plasticity index. Section B4.5 then bands the pavement design by that index: under 20 for clayey sand, 20 to under 35 for lean clay, and 35 to 55 for fat clay, with lime-treated subgrade from 20 upward. One county document covers hitting rock and reaching a plasticity index of 55 — the Balcones Escarpment, written into a pavement table. The septic side says the same at house scale: the two site evaluation holes are dug five feet deep "or to a solid rock layer."

Williamson County Subdivision Regulations adopted 4 March 2025, sections B4.4 and B4.5 — wilcotx.gov/DocumentCenter/View/15640; Williamson County OSSF Guide — wilcotx.gov/DocumentCenter/View/16734

Twenty per cent impervious cover matters twice, for two different reasons
TCEQ's Edwards rule lets a single-family residence skip an individual aquifer plan at 20 per cent impervious cover or less. Separately, Appendix B11.1 of the county's subdivision regulations waives on-site stormwater detention for "Plats with three or less lots for single family residential use, with less than 20% impervious cover per lot" and for "Plats with all lots of 2 acres or more and less than 20% of impervious cover per lot." The county defines impervious cover at section 2.22 as roads, driveways, parking areas, concrete, sidewalks, structures and buildings; TCEQ's list is rooftops, driveways, concrete pads, sheds and sidewalks. Two agencies, two definitions, the same threshold — and a plat note reserves a maximum percentage per lot on the face of the plat itself.

TCEQ, Edwards Aquifer: Private Residences; Williamson County Subdivision Regulations adopted 4 March 2025, sections 2.22, B11.1 and Appendix C10.8 — wilcotx.gov/DocumentCenter/View/15640

The county signs an Edwards Aquifer certification on every plat
Section 5.31 of the subdivision regulations requires a signature block in which the County Engineer certifies that the plat complies with "the Williamson County On-Site Sewage Facility Regulations, Construction Standards for On-Site Sewage Facility Regulations as published by the Texas Commission on Environmental Quality (TCEQ), and regulations of the Edwards Aquifer, Chapter 213 Subchapter A, Section 213.1 to 213.14 of the Texas Administrative Code, as amended," and it must be signed before final plat approval. The county's septic order gives the reason in its preamble: the Commissioners Court found "that the Edwards Aquifer is a vital source of drinking water for residents of Williamson County and the Edwards Aquifer has been identified as being susceptible to groundwater pollution." A county with no building code still puts its engineer's name to an aquifer certification.

Williamson County Subdivision Regulations adopted 4 March 2025, section 5.31 — wilcotx.gov/DocumentCenter/View/15640; Williamson County On-Site Sewage Facilities Order, preamble — wilcotx.gov/DocumentCenter/View/3109

The county is the septic agent for the whole county, cities included
TCEQ's authorised agent register returns two records for Williamson County: "WILLIAMSON COUNTY AUTHORIZED AGENT — entire County" and the TCEQ Austin regional office. No city in the county is separately listed, and TCEQ's own results page prints the rule for reading that: "Do you live within the limits of a city? Find the name of the city under the Authorized Agent column. If the city is not listed, contact the county." So septic inside Georgetown, Round Rock, Cedar Park, Leander, Hutto, Taylor, Liberty Hill and Jarrell is the county's programme, run by the County Engineer's Office at 3151 SE Inner Loop in Georgetown. The county's own septic page names the single exception: it regulates septic throughout Williamson County "except for those areas that are located within the City of Austin."

TCEQ On-Site Sewage Facility authorised agent search, county code 246 — tceq.texas.gov/permitting/ossf/aa_search.html; Williamson County On-Site Sewage Facilities — wilcotx.gov/644/On-Site-Sewage-Facilities-OSSF

An excavator grading a compacted building pad on a cleared lot, with survey stakes and a drainage swale visible.
Below the slab

The expensive surprises are in the ground, not the building

What moves a Texas budget is usually below grade, and it is soil rather than rock: shrink-swell clay. The Blackland Prairie and the Gulf Coast clays move enough between a wet season and a dry one to drive the foundation design across the state's largest markets, which is why several DFW cities require an engineer's seal on the foundation of every new house. Those are the same conditions that decide whether a septic field passes its soil and site evaluation, so the grading plan, the foundation and the drainfield get resolved together rather than one at a time. We price the dirt before we price the building.

What we build in Williamson County

All nine of our services — kits, custom plans, post-frame and steel construction, site preparation, permitting and engineering, through to turnkey builds — are available across Williamson County. What a project costs depends far more on the parcel than on square footage, so we work from your land rather than from a rate card.

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What a build looks like

Three stages every Williamson County project passes through, from a raw parcel to a finished home. Site work first, because that is where the budget is decided.

Aerial view of an undeveloped rural lot with cleared grass, a live oak and cedar elm treeline, and a pale gravel access track.
Stage one

The parcel

Zoning, setbacks, flood zone and utility access get checked before anything is drawn.

An excavator grading a compacted building pad on a cleared lot, with survey stakes and a drainage swale visible.
Stage two

Pad and permit

Clearing, grading and a compacted pad, while the submittal works through Williamson County.

A finished barndominium at dusk with warm interior lighting glowing through its large windows.
Stage three

Frame to finish

Shell erected and dried in, then systems, insulation and interior finish through to CO.

Those are the rules for Williamson County. Tell us what you want to build and we will draw it to them.

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Where we build around Williamson County

Williamson County and the rural land around it. The buildable acreage for a project this size usually sits outside the city limits, which is frequently what changes who issues your permit.

Our Williamson County service area, covering Williamson County and the surrounding rural acreage. This map marks the territory we serve, not a branch location.

Keep reading

The questions that usually come next once you know what Williamson County allows.

Barndominium Cost Guide

Sourced per-square-foot ranges by tier and by size, with a calculator built on the same figures.

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Is It Legal in Texas?

Classification, zoning, the HOA gate, and why "nonresidential farm building" does not cover a home.

Read it

How Long Does It Take?

Census build-duration data, and what actually sets the permit clock where you are building.

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Nearby areas we build in

Others we cover in this part of Texas. The permitting authority, the adopted design criteria and the zoning can all differ from one to the next.

Georgetown

Williamson County
Round Rock

Williamson County
Bell County

Bell County
Burnet County

Burnet County

Building in Williamson County: common questions

9 questions we get asked most often about building in Williamson County. If yours is not on the list, ask it directly.

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Do I need a building permit for a barndominium in unincorporated Williamson County?
Not a building permit, because the county does not issue one. Williamson County has never adopted an order applying Subchapter F of Local Government Code chapter 233, so there is no county residential building code, no plan review and no county inspector for a house. What you do need is a Certificate of Compliance from the County Engineer's Office, which is the county's floodplain determination and is required for every structure outside a mapped floodplain; a Floodplain Development Permit instead if the site is in or next to the 100-year floodplain; a septic permit; and a culvert or driveway permit if you are cutting a new drive. If the land is inside a city limit or a city's extraterritorial jurisdiction, that city is in the picture too. None of those is a code review of the building itself.
Does the shop half of the building make my septic system bigger?
In Williamson County it can, and the rule is unusually specific. Section 10(E)(10) of the county's septic order leaves a climate-controlled structure out of the wastewater flow calculation only if it is separated from the main residence, has no plumbing, and is used for storage, a workshop, an office, exercise, music, art or animal sheltering. All three conditions, not one. An attached shop, or one with a sink or a bathroom, is counted in. And section 10(A)(3) treats any structure with a shower or bath plus a kitchen as a living unit, attached or detached, classified as a separate residence for design and density. That matters twice over, because TCEQ's five-acre Edwards Aquifer exemption is written for a lot with no more than one single-family residence on it.
How much land do I need for a septic system here?
Two acres if the lot is on a private well, one acre if it is on a public water supply. Those are section 10(D)(2) of the county's own septic order and they are double the state minimums of one acre and half an acre. Then read subsection (c) before you measure: recognizable beds and banks of wet weather creeks, bodies of water and dedicated public road easements come out of the calculation, so the acreage on the deed is not always the acreage the county counts. Lots platted before 27 September 1999 fall back to the state sizing rules instead. And the acreage question has a second answer sitting behind it, because two acres puts a typical barndominium footprint, apron and drive comfortably inside TCEQ's twenty per cent impervious cover test for the Edwards Aquifer.
Is the Edwards Aquifer really an issue this far north?
Yes, and it is TCEQ's programme rather than the Edwards Aquifer Authority's — the Authority governs the San Antonio segment and does not reach here. Williamson County is named first on TCEQ's own list of the eight counties covered by the Edwards Aquifer rules in 30 TAC chapter 213, and TCEQ's chapter 213 mapping takes in around twenty United States Geological Survey quadrangle sheets inside the county, among them the Georgetown, Round Rock, Leander and Liberty Hill sheets. Which regulatory zone a particular parcel falls in is a map question, and TCEQ publishes an Edwards Aquifer map viewer for exactly that. The two zones work differently. On the recharge zone there is no acreage threshold: 30 TAC 213.5(h)(2) exempts an individual landowner building their own single-family residence or associated residential structures only where impervious cover stays at twenty per cent or less of the site, and TCEQ's private residences guidance adds a lot larger than five acres carrying no more than one residence, or rainwater harvesting that brings adjusted cover under twenty per cent. On the contributing zone the trigger is disturbance rather than lot size — section 213.21(b) applies only to regulated activities disturbing at least five acres, or less where they are part of a larger common plan of development or sale with the potential to disturb five acres cumulatively. A single house rarely reaches that. A lot inside a new subdivision is a different question, because the rule counts the whole plan. Where a parcel straddles both, the stricter zone governs.
Will I need a permit for a water well?
Not from a groundwater district, because Williamson County does not have one. The county has said so publicly, describing itself and Travis County as islands surrounded by districts — Clearwater in Bell, Post Oak Savannah in Milam, Central Texas in Burnet. That means no district registration, no district spacing rule and no production management. It also means nobody is studying the aquifer under your land: the same county publication says most western Williamson wells draw on the Trinity, which recharges at four to five per cent of rainfall, and that the county is oversubscribed west of Interstate 35. The state requirements still stand — a licensed driller and a State of Texas well report — and the county's septic order requires a hundred-foot radius around a private well in which no septic disposal unit may sit.
Where in the county is there actually land to build on?
Not evenly. Cedar Park grew 2.5 per cent in five years and is finished; Round Rock at 17.4 per cent is dense I-35 suburbia. The frontier is on the western and northern edge — Liberty Hill grew 261.9 per cent and Jarrell 228.9 per cent, with Georgetown at 55.6 and Leander at 52.7 pushing outward across the same ground. Hutto grew 63.9 per cent on the eastern side. The quietest land is further east and north still, around Granger, Thrall, Coupland, Bartlett and Florence, where the towns grew between three and eight per cent over the whole five years. Worth knowing: the unincorporated county absorbed only about three per cent of the county's growth, and seventeen city extraterritorial jurisdictions reach out across the rural land, so the first question on any tract is which authority reviews the plat.
Does the ground change across the county?
Sharply, at the Balcones Escarpment. West of roughly I-35 it is Edwards limestone with thin soil over rock, caves, faults and sinkholes — the county's septic guide tells you to dig the site evaluation holes five feet deep or to a solid rock layer, whichever comes first. East of it is Blackland Prairie clay, and the county's own subdivision regulations band pavement design by plasticity index up to 55, far above the threshold at which Texas law puts a licensed engineer on a slab foundation. The same document that talks about hitting non-fractured rock also talks about fat clay. Two different foundation problems, one county line apart, and the site evaluation is what tells you which one you have bought.
Does it change anything if I rent the barndominium out?
It may, and it is worth settling before you build rather than after. Williamson County does enforce a fire code — the 2018 International Fire Code, adopted under Local Government Code section 233.061 — but by its own terms it reaches public buildings, commercial establishments and multi-family dwellings of four or more units, and it identifies those by the current property designation given by the Williamson Central Appraisal District. So the question of whether a code applies to your building is answered by how the appraisal district classifies the property, not by the building. The code also treats a change in occupancy classification as a substantial improvement, giving the renovation of a warehouse into a loft apartment as its example. The Fire Marshal's Office is on 512-943-3601 and the appraisal district on 512-930-3787.
What is a Certificate of Compliance, and why have I been told two different things about it?
Because there are two documents with that name in this county. The County Engineer's Certificate of Compliance is a floodplain determination: it certifies that no 100-year floodplain exists in the area of proposed development, and it is required for every structure outside the floodplain in the unincorporated county. The Fire Marshal's Certificate of Compliance is a different thing entirely, defined at section 3.1 of the county fire code as a certificate that construction has been completed in compliance with that fire code for a specific occupancy, and it applies to commercial work rather than a house. If someone tells you that you need a Certificate of Compliance, ask which office they mean. For a house on rural land the answer is almost always the County Engineer's, at 3151 SE Inner Loop in Georgetown, 512-943-3330.

Building in Williamson County?

Start with the plan. Tell us what you want to build and we will draw it, then confirm what Williamson County will actually let you put on the parcel and what wind load it has to meet. That conversation costs nothing.

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