Knox County 2018 IRC with Tennessee amendments

Barndominium Builders in Knoxville, TN

Knoxville and Knox County are separate permitting authorities working out of the same building on Main Street, and they are not on the same code: the city adopted the 2024 International Residential Code in October 2024 while the county is still on the 2018 edition. Both of them, unusually for Tennessee, fill in Table R301.2 rather than leaving it blank, and their numbers match to the cell. The buildable acreage is on the county side, where the A zone permits a house on one acre with no appearance standards at all; inside the city the Estate Neighborhood district adds design tests that a stock barndominium elevation will not pass without changes.

Knoxville at a glance

County: Knox County
Population: 190,740
ZIP codes: 37902, 37909, 37912, 37914, 37915, 37916, 37917, 37918, 37919, 37920, 37921, 37922, 37923, 37924, 37931, 37932, 37934, 37938
Site visits: About 200 miles east of our Franklin office on I-40

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Building conditions in Knoxville

What actually changes from one Tennessee 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 Knoxville, drawn from the sourced facts on this page. Every figure above is cited in the quick-facts panel below, with its source and vintage.

Two permitting authorities, one address

Knoxville and Knox County permit separately, out of the same building on Main Street. City of Knoxville Plans Review and Inspections sits at 400 Main Street, Suite 475, on 865-215-4311, and covers land inside the city limits. Knox County Codes Administration is Suite 547 of the same City County Building, on 865-215-2325, and covers everything outside them. Which counter you deal with is settled entirely by the city line, and the acreage is on the county side of it.

City of Knoxville Plans Review & Inspections, permits.knoxvilletn.gov/Plans-Review-Permits, and Knox County Codes Administration, knoxcounty.org/codes, both fetched 31 Aug 2026

The city and the county are on different residential codes

Knoxville City Code section 6-41 adopts the 2024 International Residential Code, by Ordinance O-125-2024 of 29 October 2024. Knox County Code section 10-56 adopts the 2018 edition, by Ordinance O-18-10-101 of 19 November 2018, which is also the edition Tennessee uses statewide. One municipal boundary separates two editions of the same code six years apart, and Chapter 3 was renumbered between them, so a section number quoted for one side describes a different subject on the other.

Knoxville Code of Ordinances § 6-41 and Knox County Code of Ordinances § 10-56, Municode, fetched 31 Aug 2026

Table R301.2(1) is filled in here, and both authorities agree

Tennessee leaves the climatic and geographic design criteria table for each jurisdiction to complete, and most leave it blank. Knox County and the City of Knoxville both publish it in full, and every cell they share carries the same value: ground snow load 10 psf, wind speed 90 mph, no topographic effects, no special wind region, no windborne debris zone, Seismic Design Category C, severe weathering, a 12 inch frost line depth, termites moderate to heavy, winter design temperature 19 degrees Fahrenheit, no ice barrier underlayment required, air freezing index 210 and mean annual temperature 59.4.

Knox County amendments to the 2018 IRC, knoxcounty.org/codes/pdfs/IRC_ammendments.pdf, and Knoxville Code of Ordinances § 6-42, both fetched 31 Aug 2026

Termites: moderate to heavy, in both authorities' own words

Knox County's amendment document and the City of Knoxville's ordinance each insert the words moderate to heavy into the termite row of Table R301.2(1). That is the designation that sets what R318 of the 2018 code requires by way of protection against subterranean termites, and here it comes from two local primary instruments rather than from reading a national map. It is a lower band than the deep South carries, and it changes what treatment and detailing the inspector expects at the slab edge and at every point where wood approaches grade.

Knox County amendments to the 2018 IRC, knoxcounty.org/codes/pdfs/IRC_ammendments.pdf, and Knoxville Code of Ordinances § 6-42, fetched 31 Aug 2026

Septic permits come from the county health department

Knox County runs its own subsurface sewage programme rather than sending applicants to the state. The Knox County Health Department Groundwater Division at 140 Dameron Ave, on 865-215-5200 extension 1, issues the installation permit and the drain field layout. It requires soil maps completed by a licensed soil consultant plus a site plan showing property lines, house site, planned driveways and utilities, and it asks for the bedroom count and whether there is a basement. Published fees are $40 for a lot evaluation, $200 for the installation permit and drain field layout, and no charge for a repair permit.

Knox County Health Department, Groundwater Services, knoxcounty.org/health/groundwater_protection/groundwater_services.php, fetched 31 Aug 2026

The city's EN district design standards, which a stock plan fails

Inside the city, the Estate Neighborhood district is the large-lot district at a 22,000 square foot minimum, and it is exactly where a barndominium would go. Section 4.4 requires a primary structure to meet two of three tests: a roof either flat under 1/12 on a single plane, steep at 6/12 or more, or articulated with multiple pitches, planes, ridge line directions or heights; more than one finished floor level; or a habitable and attached garage shape of no fewer than eight sides. A single-storey rectangle with a 4/12 gable satisfies none of the three. Street-facing elevations must also carry window and door systems over at least 25 percent of the façade, with no more than 24 feet of continuous wall on the front without a recess, projection or integrated covered porch.

City of Knoxville Zoning Code, Appendix B, Article 4, § 4.4 EN District Standards, Municode, fetched 31 Aug 2026

Also worth knowing before you build in Knoxville

Knox County's A zone permits houses on one acre: In the county's A, Agricultural zone, section 5.22.02 permits houses and duplexes outright, with no use-on-review hearing. Section 5.22.04 sets a minimum lot area of one acre per house, 100 feet of lot width at the building line, a 40 foot front yard, 10 foot side yards for a single-storey dwelling, a 35 foot rear yard and 30 percent maximum lot coverage. Main buildings may reach three storeys or 35 feet. There is no minimum heated floor area anywhere in the district.
The 18 foot cap on detached accessory buildings: Knox County caps accessory buildings at 18 feet and measures it strictly. Section 5.22.05 reads that in no case shall the bottom chord of the roof truss or the bottom of the ceiling joist of an accessory building exceed eighteen feet in height, so the limit is not to the ridge. A detached shop sized around a tall door and its header reaches that quickly. A shop attached to and forming part of the dwelling falls under the main building limit of three storeys or 35 feet instead, which is one good reason to look at the attached layout first on a Knox County parcel.
Neither authority names barndominiums or restricts cladding: The word barndominium appears nowhere in the Knox County zoning ordinance or in Chapter 6 of the Knoxville city code, and neither instrument restricts the exterior wall material of a site-built dwelling. The county ordinance's only exterior materials clause sits inside the Town Center zone development plan checklist, which does not reach houses on acreage. The city's only material requirement in the residential article is that an Estate Neighborhood foundation be surrounded by a perimeter wall of solid masonry, concrete or other approved material, which governs the foundation skirt rather than the walls above it.
Sprinklers optional, smoke alarms required in the garage: Knox County amended R313 to make automatic fire sprinkler systems optional in one- and two-family dwellings and in townhouses alike, which reaches further than the state amendment does on its own. It went the other way on R314.3, amending it to require smoke detectors in garages. That is an addition beyond the model code, it is specific to this county, and it is an easy inspection to fail if the electrical layout does not allow for it.
Energy requirements roll back to 2009-era tables: Knox County amended its insulation and fenestration table so that existing R-values remain in force: walls R-13, ceilings R-38, floors R-19, and ducts R-8 in attics and R-6 in all other areas. It removed blower door testing and duct blower testing outright, along with mandatory whole-house ventilation and programmable thermostats. The city takes the same route, replacing its insulation and equivalent U-factor tables and its testing section with the 2009 edition's. Envelope and duct-tightness figures quoted from national articles overstate what is actually enforced here.
Valley and Ridge geology: rock depth changes across one footprint: Knoxville sits in the Valley and Ridge, which the USGS describes as a strongly folded and faulted belt of alternating ridges and stream valleys, where dissolution openings reach 180 metres or deeper because the rock units are not horizontal, and where the Knox dolomite forms knobby ridges under chert-capped residual cover tens of metres thick. The beds stand at an angle rather than lying flat, so depth to competent rock can differ markedly between one end of a long footprint and the other. On a clear-span building, where the whole roof load arrives at a handful of column bases rather than spreading along continuous bearing walls, that is a differential settlement question, and it is why the boring plan earns its keep on this site type.
How Knox County values a permit: Since 1 July 2024 Knox County has valued a one- and two-family type VB dwelling for permit purposes at a 60 percent factor of the most current ICC Building Valuation Data report, replacing the flat per-square-foot basis it used before. Permitting runs through the county's online portal, plans larger than 11 by 14 inches must be submitted as PDF, and a 2.50 percent convenience fee applies to card payments and is taken by the processor rather than the county.
Climate zone 4A, and what it changes: The Tennessee residential code assigns Knox County to climate zone 4A. Only twelve counties in the state, all of them in the west, sit in 3A. Zone 4A drives the envelope and equipment specification, and it is the reason a barndominium here needs a genuine plan for insulating a tall clear-span volume rather than the shallower assemblies that suit warmer parts of the state.

Below the slab

The expensive surprises are in the ground, not the building

What moves a Tennessee budget is usually below grade: limestone sitting shallow, karst voids and sinkholes, and slope. Those are the same conditions that decide whether a septic field passes its soil and site evaluation, so the grading plan, the footing depth 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 Knoxville

All nine services are available across Knox County. What a build costs depends far more on the parcel than on square footage, so we price against your land rather than publishing a rate card.

Barndominium Kits

Engineered barndominium shell packages delivered to your Tennessee lot, stamped for the criteria your county adopted.

Turnkey Builds

Start to finish barndominium construction: we handle permits, slab, shell, and full interior finish.

Custom Plans

Barndominium floor plans drawn to your land, your family, and the residential code your county actually enforces.

Post-Frame Homes

Pole barn construction adapted into full residences, with wide clear spans and fast dry-in.

Steel Construction

Red-iron and light-gauge steel framing: no rot, no termites, engineered to your county’s adopted wind criteria.

Shouses

Shop and house in one building: workspace and living space under a single roof and a single permit.

Metal Homes

Full metal-clad residences: low maintenance envelopes specified to your Tennessee climate zone.

Site Preparation

Clearing, grading, pad, drainage, and utilities: the work that decides whether the build goes smoothly.

Permitting & Engineering

Sealed structural engineering and the permit that depends on it, from submittal through final inspection.

What a build looks like

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

Stage one

The parcel

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

Stage two

Pad and permit

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

Stage three

Frame to finish

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

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

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Where we build around Knoxville

Knox 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 Knoxville service area, covering Knox County and the surrounding rural acreage. We build across this area from our office in Franklin, TN — this map marks the territory we serve, not a branch location.

Keep reading

The questions that usually come next once you know what Knoxville 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 Tennessee?

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

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How Long Does It Take?

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

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Sources for this page

The primary documents behind the Knoxville figures above. We would rather you checked them than took our word for it.

Nearby areas we build in

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

Building in Knoxville: common questions

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

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Who issues my building permit, the City of Knoxville or Knox County?

Whichever one the parcel sits in. Inside the city limits it is the City of Knoxville Plans Review and Inspections, 400 Main Street, Suite 475, on 865-215-4311. Outside them, anywhere in unincorporated Knox County, it is Knox County Codes Administration in Suite 547 of the same City County Building, on 865-215-2325. Farragut permits its own area separately again. The State Fire Marshal's Office lists all three with a status of exempt, which in Tennessee means each has certified that it adopts and enforces its own codes rather than leaving residential permits to the state. So there is a local inspector either way, and there is no opt-out resolution here whose expiry date has to be watched.

Which edition of the residential code applies to my build?

It turns on the same city line. The City of Knoxville adopted the 2024 International Residential Code in October 2024. Knox County is on the 2018 edition, adopted in November 2018, which is also the edition Tennessee applies statewide. The difference is not cosmetic: Chapter 3 was renumbered between the two editions, so a section number that means one thing in the county means something else in the city, and a plan set drawn to city requirements is not automatically drawn to county ones. Settle which authority will stamp the permit before the drawings are finished, and cite the edition it actually enforces.

What design criteria will my engineer work to in Knox County?

Unusually for Tennessee, they are published rather than left blank. Knox County and the City of Knoxville both fill in Table R301.2(1) with the same values: ground snow load 10 psf, wind speed 90 mph, Seismic Design Category C, severe weathering, a 12 inch frost line depth, termites moderate to heavy, a winter design temperature of 19 degrees Fahrenheit, no ice barrier underlayment required, an air freezing index of 210 and a mean annual temperature of 59.4. A clear-span barndominium exceeds the prescriptive tables whatever those numbers say, so under R301.1.3 it is designed by a Tennessee-licensed engineer in accordance with accepted engineering practice. The engineer starts from the published figures and confirms with the authority which edition of ASCE 7 the wind speed is referenced to.

Do I need a septic permit, and who issues it?

If the site is not on public sewer then yes, and in Knox County it comes from the county health department rather than from the state directly. The Groundwater Division at 140 Dameron Ave, on 865-215-5200 extension 1, issues the subsurface sewage disposal system installation permit and the drain field layout. It wants soil maps prepared by a licensed soil consultant and a site plan showing property lines, house site, planned driveways and utilities, and it asks for the bedroom count and whether there will be a basement, both of which change the answer. Published fees are $40 for a lot evaluation and $200 for the installation permit and drain field layout. Inside the city there is a further rule: any residential lot without sanitary sewer must be at least 20,000 square feet. Get the soil work done before you commit to a house position on the site, not afterwards.

Will a standard barndominium design pass in Knoxville?

In unincorporated Knox County it is straightforward. The A, Agricultural zone permits houses outright on a one acre minimum lot, sets no minimum heated floor area, imposes no minimum roof pitch and places no restriction on what the walls are clad in. Inside the city it is harder. In the Estate Neighborhood district a primary structure has to meet two of three tests on roof form, number of finished floor levels and building shape, and a single-storey rectangle with a 4/12 gable meets none of them. It also needs windows and doors across at least a quarter of every street-facing elevation and no run of front wall longer than 24 feet without a recess, a projection or an integrated covered porch. All of that is buildable, with a 6/12 pitch, a deep porch, dormers or a masonry band, but it has to be designed in from the outset. On an irregular lot, where planning staff determine that the building site cannot be seen from the street, the standards may be waived.

Can I put the workshop in a separate building?

You can, but Knox County caps a detached accessory building at 18 feet and measures it to the bottom chord of the roof truss or the bottom of the ceiling joist rather than to the ridge. A detached shop sized around a tall door and its header runs into that limit quickly. A shop that is attached to and forms part of the dwelling is governed by the main building limit of three storeys or 35 feet instead, which is one good reason to look at the attached layout first on a county parcel. Inside the city there is a separate constraint: accessory structures other than accessory dwelling units may not be used for occupancy at all, so living in the shop while the house goes up is not available within the city limits.

Do I need a licensed contractor to build a barndominium here?

Tennessee requires a contractor's licence for projects of $25,000 or more as prime contractor, and the state counts the complete project cost including labour and materials. Separate phases, purchase orders or contracts cannot be used to stay under the threshold. The residential classifications that matter are BC-A, BC-A/r restricted residential which is capped at $125,000, and the combined BC. A property owner may build on their own property for their own personal use, though that exemption does not extend to commercial construction. Almost any barndominium clears $25,000, so for most readers the real question is not whether the threshold applies but who is carrying the licence on the contract.

What clients say

4.9 out of 5 based on 8 reviews Placeholder content

Steel framing was the whole reason we went this route after termites went through our last place. Straight answers about what the envelope would and would not do in Tennessee humidity.

Curtis A. January 22, 2026

We had ten acres outside town and no idea what we could legally put on it. They pulled the zoning and the A-1 lot minimum before we spent anything on drawings, which saved us from buying plans for a building that would not have been approved.

Dale W. July 18, 2026

Ordered the shell kit and erected it with my brother-in-law over about six weekends. The drawings were clear, the bolt schedule matched what showed up on the truck, and the county inspector had no issues with the engineering.

Marisol T. June 2, 2026

Building in Knoxville?

Start with the plan. Tell us what you want to build and we will draw it, then confirm what Knox 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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