Buchanan County No code adopted here

Barndominium Builders in Buchanan County, MO

Buchanan County is 408.249 square miles of wind-blown silt above the Missouri River, and almost all of the land is outside the city. St. Joseph holds 71,098 of the county's 83,574 residents on 44.036 square miles; the unincorporated balance is 11,018 people spread across everything else, farming 140,427 acres on 619 holdings that average 227 acres. That gap between where the people are and where the land is defines the county page, because the rules change at the city line and not at the county line. Inside St. Joseph the city permits and inspects against the 2018 International Residential Code and a full companion set. Outside it, Buchanan County has adopted no building code at all — and its own 2022 Comprehensive Plan lists adopting one as a strategy still to be carried out. What the county does have is a Zoning Order that reaches the entire unincorporated area, and that Order is not a formality. Section 109.115.3 requires a building permit for any structure in every zoning district regardless of acreage, and states that failing to get one can result in the demolition of the structure. Section 203 sets the minimum lot area for a dwelling in the A-1 General Agricultural District at twenty acres. The Environmental Inspector permits and inspects the septic system, the floodplain article requires the lowest floor of a new house in an A or AE zone to sit a foot above base flood elevation, and the County Road Supervisor sizes the driveway tube. So the honest answer for a buyer here is not that nobody is watching. It is that the county checks where the building sits, how big the parcel is, where the sewage goes and how high the floor is — and leaves how the building is framed, braced and insulated to the owner and to whoever seals the drawings.

Buchanan County at a glance

County: Buchanan County
Cities & counties covered: Buchanan County 83,574 · City of St. Joseph 71,098 · Balance of Buchanan County (unincorporated) 11,018
Site visits: Same-week site visits across the unincorporated county — the Missouri River bottom ground west toward Rushville and Lewis and Clark Village, the loess ridges east toward Easton, and the open country south around Faucett, Agency and De Kalb

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Building conditions in Buchanan County

Missouri sets no residential building code and no statewide way of adopting one, so the first question on any parcel is not what the code says — it is whether there is one. Only counties of the first and second classification may adopt a building code at all, and classification is set by assessed valuation rather than population, so a small county can hold the power while a much larger one does not. Zoning is a separate power with its own answer, granted only after a vote of the people and repealable by another. What changes from one jurisdiction to the next is whether the work is inspected, who issues the permit, what that office charges, how the parcel is zoned, and the design figures your drawings have to satisfy.

Build conditions for Buchanan 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 is allowed a building code, has never adopted one, and says so in its own plan

Buchanan County is first classification, and RSMo 64.170.1 empowers the county commission in counties of the first and second classification to adopt regulations controlling construction and to issue building permits. Buchanan County has that power and has not exercised it. The strongest evidence is the county's own: its adopted 2022 Comprehensive Plan, prepared with the Mo-Kan Regional Council, lists under Housing Objective 2 the strategy 'Adopt a building code for new homes and minimum housing standards to pressure the quality of older homes and subdivisions' — a recommendation the county would have no reason to write down if it already had one. Nothing in the Zoning Order, the Subdivision Regulations or the Land Use Regulations adopts a building, residential, electrical, plumbing, mechanical or energy code. The statute also sets out what adoption would take from here: RSMo 64.170.2 provides that a county which had not adopted a building code before 28 August 2001 needs voter approval first, and RSMo 64.170.3 restricts that vote to the area the code would affect, so residents of incorporated territory do not vote on it.

RSMo 64.170 (RSMo 1939 § 14942; A.L. 1945; A.L. 1963; A.L. 1999; A.L. 2001 S.B. 86; A.L. 2008 S.B. 1181), Effective 28 Aug 2008, rendered from revisor.mo.gov 8 September 2026; Buchanan County Comprehensive Plan, adopted 2022, Housing Objective 2 Strategy 2.3, page 116, retrieved from co.buchanan.mo.us 8 September 2026; Buchanan County Zoning Order as amended (January 2026 reprint incorporating amendments to December 2025) and Buchanan County Subdivision Regulations 2016, both read in full 8 September 2026; classification from the Missouri Association of Counties, 'Missouri Counties by Classification', published May 2025

Every structure needs a county permit anyway, and the stated remedy for skipping it is demolition

The absence of a building code is not the absence of a permit. Zoning Order § 804 provides that no building shall be erected, constructed, reconstructed, moved or demolished, nor altered, without first applying for and being issued a building permit. Section 109.115.3 puts it beyond argument: 'All Zoning Districts, regardless of acreage, require a building permit for any structure and on-site wastewater treatment, if applicable. Failure to secure a building permit or follow proper setbacks, right of ways and all Density Table Requirements can result in the demolition of the structure(s).' The county's own Permits and Licenses index states the threshold in plainer terms — the Planning and Zoning Office issues permits for 'Any Buildings Over 100 sq. ft.' The Zoning Officer must act on an application within thirty days or the applicant may appeal to the Board of Zoning Adjustment (§ 804.1.2); the permit is posted on the site and displayed for thirty days after completion (§ 804.1.4); it expires after a year (§ 804.1.5); and building first and applying afterwards doubles the fee (§ 804.1.9). What the permit checks is compliance with the Zoning Order — district, use, setbacks, density, septic, floodplain — not framing, footings or wiring, because the county has adopted no standard for those.

Buchanan County Zoning Order §§ 109.115, 109.115.3 (revised 11 May 2018), 804, 804.1.2, 804.1.4, 804.1.5 and 804.1.9 (amended June 1985), January 2026 reprint incorporating amendments to December 2025, downloaded as PDF from co.buchanan.mo.us and read 8 September 2026, with §§ 109.115 and 701 re-extracted independently page by page and confirmed identical; Buchanan County Permits and Licenses index, co.buchanan.mo.us, read 8 September 2026

A house on general agricultural ground needs twenty acres

The Agricultural Density Requirements Table at Zoning Order § 203 sets the minimum lot area for Dwellings in the A-1 General Agricultural District at twenty acres as a permitted use, amended to that figure on 15 August 2012. A dwelling on less than twenty acres in A-1 is a conditional use with a one-acre minimum, which means a public hearing before the Planning and Zoning Commission, a $350 application fee plus notification and legal advertising, and a permit that goes void if substantial action is not taken within three years. In the A-OR Agricultural-Outer Residential District a dwelling needs two acres — raised from one acre by County Commission order of 25 March 2026, to line the Density Table up with § 109.115.1. In A-2 Commercial Agricultural a dwelling is not a permitted use at all. Two narrow exceptions cut through without rezoning, both requiring at least two acres: § 205 issues a permit where the builder is a sibling, parent, child or grandchild of the parcel's owner, and § 206, amended December 2025, issues one where an existing single-family dwelling on the site has been or will be demolished within a year. And the county's adopted comprehensive plan explains the policy behind the acreage: applications before Planning and Zoning 'will be viewed in the context of converting no more farmland to residential development than what is necessary.'

Buchanan County Zoning Order § 203 Agricultural Density Requirements Table (amended 15 August 2012), §§ 109.115.1 (amended 17 May 2019), 205 (amended June 1998), 206 (amended December 2025), 805.6.1 and 806.8, January 2026 reprint; County Commission of Buchanan County, order of Wednesday 25 March 2026, January Term 2026, adopting Items 4 to 9 recommended by the Planning and Zoning Commission on 18 March 2026, signed by the three commissioners and certified by County Clerk Mary Baack-Garvey, PDF read 8 September 2026; Buchanan County Comprehensive Plan 2022, Future Land Use, page 96

The permit fee schedule prices a farm building differently from a garage

Buchanan County publishes its whole permit fee schedule in the Zoning Order, and for a house-plus-shop build the interesting line is not the house. A single-family dwelling, whether stick-built, modular or a manufactured home, is fifteen cents per square foot of finished living space. A detached garage, shed or other accessory structure is also fifteen cents per square foot, with no cap. But a farm or agricultural structure is fifty dollars for the first five hundred square feet and ten cents per square foot after that, capped at five hundred dollars — a rule added on the same day in January 2017 that the accessory-structure line was amended, which is to say the county drew the distinction deliberately. Commercial and industrial buildings run twenty cents per square foot; other structures are one percent of estimated construction cost with a fifty dollar minimum; a residential land disturbance permit is one hundred dollars and a demolition permit fifty. Churches, schools, not-for-profit charitable institutions and government subdivisions pay nothing. Fees are not refundable.

Buchanan County Zoning Order § 805 Fee Schedule (amended 4 October 2010), §§ 805.1.1, 805.1.4 (amended 1 January 2017), 805.1.4.1 (added 1 January 2017), 805.1.5, 805.1.6, 805.1.7, 805.1.8, 805.1.9, 805.5.1 and 805.8, January 2026 reprint incorporating amendments to December 2025, read 8 September 2026; the 25 March 2026 County Commission order repealed § 705.4.7.5 and left § 805 untouched

Nothing in the zoning code tells you what the building has to look like

Read straight through, the Buchanan County Zoning Order and its Table of Uses contain no exterior material restriction, no minimum roof pitch, no eave projection requirement, no architectural or appearance review, and no minimum dwelling floor area. The only mentions of metal in either document are industrial use categories — metal plating, metal smelting, fabricated structural metal products. A steel-skinned or post-frame house faces no material objection here, which is worth knowing because it is not true everywhere in this part of the state. The accessory-building rule takes an unusual shape too. Section 701 permits accessory buildings in any district and caps them by coverage rather than by size: no single detached accessory building may occupy more than thirty percent of the required yard spaces in the rear half of the lot, and all of them together no more than forty percent, with no square-foot maximum anywhere in the Order. It must stay out of the required front yard and at least ten feet from the dwelling. And in A-1 and A-2 the Density Table sets no maximum height for either a principal or an accessory building — the 35-foot cap applies only in A-OR and the residential districts.

Buchanan County Zoning Order §§ 203, 303, 701 and 703, and the Buchanan County Table of Uses as amended October 2025, both read in full 8 September 2026, with § 701 re-extracted independently from page 57 of the Order and confirmed identical; the county's Classes of Districts sheet (Buchanan County Planning and Zoning, 2019) lists the sixteen district symbols the Table of Uses columns refer to

Deep loess, almost no rock, and one of eleven radon Zone 1 counties in the state

The ground here is wind-blown silt, and the survey data says how much. Of the 265,255 acres in the USDA soil survey of Buchanan County, 127,961 acres are mapped to components whose parent material is recorded simply as loess, with thousands more under layered loess-over-till and loess-over-paleosol groups. The two largest components are Knox at about 54,400 acres and Marshall at about 41,500, both formed in loess; the Official Series Description puts Knox on 'strongly dissected hills and bluffs bordering the Missouri River Valley and its tributaries' with slopes of 2 to 35 percent. Their measured texture is what a footing designer needs: 61 to 73.5 percent silt through every horizon, under 6 percent sand anywhere, and clay from 20 to 35 percent, running to depths of 150 to 200 centimetres. Bedrock is very nearly a non-issue — only about 6,670 component-weighted acres, roughly 2.5 percent of the survey area, carry a lithic or paralithic restriction within 20 inches, and about 13,250 acres within 40 inches. What replaces rock as the constraint is radon: the EPA's Map of Radon Zones dataset assigns Buchanan County Zone 1, the highest of three, where average indoor levels may exceed 4 picocuries per litre. Eleven of Missouri's 114 counties carry Zone 1 and Buchanan is one of them. Passive sub-slab depressurisation is cheap to rough in before the pour and expensive to retrofit afterwards, and no county inspector here will raise it.

USDA-NRCS Soil Data Access, survey area MO021 (Buchanan County, Missouri), tabular queries run 8 September 2026 against the legend, mapunit, component, chorizon, copmgrp and corestrictions tables, with a bogus survey area returning an empty result as a control; USDA-NRCS Official Series Descriptions for KNOX and MARSHALL, soilseries.sc.egov.usda.gov, read 8 September 2026; U.S. Environmental Protection Agency, Map of Radon Zones county spreadsheet (radon_zones-spreadsheet.xls, last saved 22 September 2025), downloaded from epa.gov and parsed 8 September 2026 — Buchanan, MO reads Zone 1

Also worth knowing before you build in Buchanan County

Septic is a county ordinance, and the three-acre state exemption is not a safe assumption: The Missouri Department of Health and Senior Services names the permitting authority for on-site wastewater in Buchanan County as the 'Buchanan County Commission (everything except City of St. Joseph)', authority type Ordinance, at 411 Jules Street — the state's own record of where the county line of authority runs, drawn at the St. Joseph city limits. The ordinance sits inside the Zoning Order at § 721.2.2. It adopts RSMo 701.025 to 701.059 and 19 CSR 20-3.080 by reference, and then requires that 'all persons engaged in the construction, major modification or major repair of an on-site sewage disposal system in Buchanan County shall obtain a permit from the Buchanan County Environmental Inspector' — with the Inspector empowered to inspect up to one hundred percent of systems, and to uncover an unnotified installation at the owner's expense. RSMo 701.031 excludes a single-family lot of three acres or more from the state programme, but RSMo 701.047 lets a county adopt more restrictive standards than the state's, so the acreage argument is a question for the Environmental Inspector rather than an answer. Two county figures are firm: in A-1, A-2 and A-OR a septic system needs a total area of at least 43,560 square feet — one acre — and in every other district the area is set by a soil morphology test that must be done before a building permit can issue.
Five fire protection districts, and a statute that stops them being the building department: The Missouri fire department registration list for 2026 records five Chapter 321 fire protection districts serving Buchanan County — Southwest Buchanan County at Rushville, South Central Buchanan County at Agency, Easton, DeKalb and San Antonio — alongside the St. Joseph Fire Department, the Rosecrans air base department and the Region H hazardous materials team. In some Missouri counties a district has stepped into the gap a county code leaves and become the construction authority. That route is closed here, and the statute is explicit about why. RSMo 321.228.1(2) defines a 'residential construction regulatory system' to include any county ordinance, order or rule pertaining to residential construction, any permitting programme relating to it, and any inspection programme. Buchanan County's Zoning Order is exactly that. Subsection 2 then provides that where a county adopts, implements and enforces such a system, fire protection districts wholly or partly inside it are 'without power, authority, or privilege to enforce or implement' one, and any they adopt is advisory only. What the districts keep is real but narrow: final say on fire hydrant location, specification and flow rates and on fire lanes; the right to inspect the alteration, enlargement, replacement or repair of a one- or two-family dwelling, though not new construction; and no fee for either. None of the five publishes an adopted building or residential code.
The one construction standard the county does impose is a foot of freeboard: The Missouri River runs the whole western edge of the county and the floodplain articles of the Zoning Order — §§ 610 to 621 — are where the county comes closest to regulating how a house is built. No development is permitted in a numbered or unnumbered A zone or an AE zone except through a floodplain development permit granted by the County Commission or its designee, and § 614.2 requires new or substantially improved residential construction, manufactured homes included, to have the lowest floor including basement elevated to one foot above base flood elevation. That is a foot of freeboard above the National Flood Insurance Program minimum, and it is the only dimensional construction requirement the county sets for a dwelling. Buchanan County has been in the NFIP regular programme since 1 August 1978 under community number 290040, and FEMA's Community Status Book gives 13 November 2026 as the map date for every community in the county. Five of the six communities listed participate; the City of Easton does not, and carries an initial Flood Insurance Rate Map date of 13 November 2026 with a sanction date a year later. How much of the county this reaches is measurable: of 265,255 acres in the soil survey, about 40,600 component-weighted acres are rated occasionally flooded and about 11,300 frequently flooded, with a further 39,700 rated rare.
Where the county's rules stop, and what replaces them: A county code adopted under RSMo 64.170 to 64.200 reaches only unincorporated territory under RSMo 64.180, and the Buchanan County Zoning Order draws the same line for itself at § 105: the area governed is 'the entire unincorporated area of Buchanan County, Missouri.' In Buchanan County that boundary is unusually consequential, because the incorporated share is one city and a handful of villages. Of 83,574 residents in 2024, the Census Bureau puts 71,098 inside St. Joseph, 653 in Agency, 239 in De Kalb, 226 in Easton, 218 in Rushville, 92 in Lewis and Clark Village, 30 in the Buchanan portion of Gower and none at all in the Buchanan portion of Dearborn — leaving 11,018 in the unincorporated balance. On land it runs the other way: St. Joseph occupies 44.036 of the county's 408.249 square miles. So most of the people are inside a city that permits and inspects against the 2018 International Building, Existing Building, Residential, Mechanical and Fuel Gas Codes, the 2018 Uniform Plumbing Code, the 2018 International Fire Code and the 2017 National Electrical Code — and most of the ground is outside it, under a zoning permit and nothing else.
Splitting off a building site: five acres is the line that matters: Buchanan County's Subdivision Regulations define a subdivision as the division of a tract into two or more lots for sale or development where a street is to be dedicated, reserved, platted, opened or constructed — 'except the division of land into two (2) parcels greater than five (5) acres each shall be exempt from these regulations', an exemption amended into the definition on 12 October 2011. Separately, § 203.1 lets a single dwelling built on a tract of forty acres or more before January 2000 be separated onto one or more acres without rezoning to residential. Neither exemption reaches the building permit: § 109.115.2 states that twenty or more acres is not subject to rezoning, but a building permit and an approved on-site sewage system are still required. And once a parcel is settled, § 109.116 puts the driveway in the county's hands as well — road and driveway cuts are sized and approved by the County Road Supervisor, with the landowner paying for the culvert tube and the county installing it.
The land: 619 farms, 140,427 acres, and a quarter of it gone in five years: The 2022 Census of Agriculture counts 619 farms in Buchanan County working 140,427 acres at an average of 227 acres. Cropland accounts for 99,276 of those acres, pastureland 19,667, woodland 10,008 and other uses 11,476. The distribution is the useful part for anyone shopping for a building site: 41 holdings run 1 to 9 acres, 193 run 10 to 49, 236 run 50 to 179, and only 59 exceed 500 acres. That is a county of small and mid-sized parcels rather than one of large blocks, which suits a house-and-shop build and sits awkwardly against the A-1 district's twenty-acre minimum for a dwelling. The trend is sharper still: land in farms fell 24 percent and the number of farms 22 percent between 2017 and 2022, while average farm size held almost flat at minus 2 percent — the signature of holdings leaving agriculture whole rather than being consolidated.

Below the slab

The expensive surprises are in the ground, not the building

What moves a Missouri budget is usually below grade, and which problem you have depends on where in the state you are. Across the Ozarks it is karst: the Department of Natural Resources maps more than sixteen thousand sinkhole points, and what matters there is what is under the slab rather than what the slab sits in. Across the north and centre it is claypan — dense, slow-draining subsoil that perches water above it for months of the year. In the Bootheel it is deep alluvium carrying the highest seismic demand in the state, where the same soils modelled for liquefaction attack post embedment and slab bearing rather than the frame above them. The same ground then decides the septic system, and Missouri does not run that on a percolation test alone: the rule allows a perc test or a soil morphology examination in a profile pit, and the authority reviewing your parcel picks which. Where a drainfield sits near a sinkhole's drainage, perc testing on its own is not permitted at all. Whether that authority is the state or your own county is itself a local question, and it changes what you have to file. So the site work, 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 Buchanan County

All nine services are available in Buchanan 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.

Custom Plans

Barndominium floor plans drawn to your parcel and your soil, and to whichever Missouri authority — a county, a city, or none at all — will review them.

Barndominium Kits

Barndominium shell packages delivered to your Missouri land, drawn to the criteria your own county or city publishes — because the state publishes none.

Turnkey Builds

Start to finish barndominium construction in Missouri: the permits that genuinely apply, site work, shell and interior finish, under one contract.

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What a build looks like

Three stages every Buchanan County 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 whichever office issues the permit where you are building.

Stage three

Frame to finish

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

Those are the rules where you are building in Buchanan County. Tell us what you want to build and we will draw it to them.

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Where we build around Buchanan County

Buchanan 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.

The Buchanan County service area, including the rural acreage outside the built-up edge, which is where the parcels big enough for a build like this usually sit. The map marks the territory we build in. It is not a branch location, and there is no office at this pin.

Keep reading

The questions that usually come next once you know what Buchanan 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 Missouri?

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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Nearby areas we build in

Others we cover nearby, and they are not interchangeable. One may be a county with an adopted building code, another a county with no legal authority to have one, another a city that permits inside its own limits whichever county the land sits in. So the office that issues the permit, whether anyone inspects the work at all, the fees, the zoning and the design figures can differ from one card to the next — sometimes across a single property line.

St. Joseph

Buchanan County

Platte County

Building in Buchanan County: common questions

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

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Does anyone inspect a house built in unincorporated Buchanan County?

The county does not inspect the building itself, because it has adopted no building code to inspect against. What it does inspect and approve is narrower and still mandatory. The Planning and Zoning Department issues a building permit for any structure in any zoning district regardless of acreage, and checks the district, the use, the setbacks, the lot area and the density requirements before it does. The Buchanan County Environmental Inspector permits the septic system and may inspect up to one hundred percent of installations, and will uncover a system installed without notice at the owner's expense. In a mapped flood zone the county requires a floodplain development permit and a lowest floor a foot above base flood elevation. The County Road Supervisor sizes and approves the driveway cut. Nobody employed by the county checks the footing depth, the header spans, the wind bracing or the wiring. That is the honest shape of it: several real approvals, none of them a structural inspection.

How much land do I need to build a house here?

In the A-1 General Agricultural District, which covers most of the open country, the Zoning Order's Density Table sets twenty acres as the minimum lot area for a dwelling as a permitted use. Below twenty acres a dwelling in A-1 becomes a conditional use with a one-acre minimum, which means an application, a public hearing before the Planning and Zoning Commission, a $350 fee plus notification and legal advertising costs, and a permit that lapses if substantial action is not taken within three years. In the A-OR Agricultural-Outer Residential District a dwelling needs two acres, raised from one acre by County Commission order on 25 March 2026. In A-2 Commercial Agricultural a dwelling is not a permitted use. There are two narrow ways through at two acres without rezoning: where the person building is a sibling, parent, child or grandchild of the parcel owner, and where an existing house on the site has been or will be demolished within a year. The practical first step on any parcel is finding out which district it actually carries, because the answer moves between twenty acres and two.

Can I put up a metal building and live in it?

Nothing in the Buchanan County Zoning Order stops you on appearance grounds. Read through the Order and the Table of Uses there is no exterior material restriction, no minimum roof pitch, no eave projection requirement, no design or appearance review and no minimum dwelling floor area — the only mentions of metal are industrial manufacturing use categories. What governs instead is the district and the acreage. A dwelling has to be a permitted or conditional use in the district the parcel carries, and it has to meet the lot area in the Density Table. And the distinction the county does draw is between a dwelling and a farm building: farm structures and structures clearly incidental to farm operations sit outside the district regulations under §§ 210, 220 and 230, and the fee schedule prices a farm or agricultural structure at a $500 cap while an accessory garage or shed runs fifteen cents per square foot with no ceiling. A building put up as a farm structure and later lived in is a different thing from the one that was permitted.

Is there a limit on how big the shop can be relative to the house?

Not by floor area, which is unusual. Section 701 of the Zoning Order caps detached accessory buildings by coverage rather than size: no single accessory building may occupy more than thirty percent of the required yard spaces in the rear half of the lot, and all of them together no more than forty percent. There is no square-foot maximum anywhere in the Order and no ratio between shop and house. Two other numbers help a large building. In A-1 and A-2 the Density Table records no maximum height at all for principal or accessory buildings — the 35-foot cap applies in A-OR and the residential districts. And the agricultural setbacks are 50 feet front, 15 feet side and 75 feet rear, with a required 10-foot separation between a detached accessory building and the dwelling. On a wide agricultural parcel those are the numbers that decide the footprint, not a floor-area cap.

My lot is over three acres — do I still need a septic permit?

Assume yes and confirm with the county. RSMo 701.031 excludes a single-family residence lot of three acres or more from the state on-site wastewater programme, but that is a state floor, not a ceiling: RSMo 701.047 lets a county adopt standards more restrictive than the state's, and the Department of Health and Senior Services records Buchanan County's authority type as Ordinance rather than as a state-run or contracted programme. The county's ordinance sits in the Zoning Order at § 721.2.2 and requires a permit from the Buchanan County Environmental Inspector from all persons constructing, majorly modifying or majorly repairing an on-site system in Buchanan County, without stating an acreage exclusion of its own. Two county requirements are fixed either way: in the agricultural districts a septic system needs a full acre of area, and in every other district the required area is set by a soil morphology test that has to be completed before the building permit can issue. The permitting authority for everything outside the St. Joseph city limits is the county; inside them it is the City of St. Joseph Health Department.

What changes the moment I cross into St. Joseph?

Everything about construction. A county building code adopted under RSMo 64.170 to 64.200 applies only to unincorporated territory under RSMo 64.180, and the Buchanan County Zoning Order sets its own reach the same way at § 105. Inside the city limits the City of St. Joseph permits and inspects against its own adopted set — the 2018 International Building, Existing Building, Residential, Mechanical and Fuel Gas Codes, the 2018 Uniform Plumbing Code, the 2018 International Fire Code and the 2017 National Electrical Code. Outside them there is no adopted construction code, no plan review against one and no published design criteria table, because there is no code for such a table to sit inside. That is why a wind speed or frost depth quoted for the city is not a figure for a parcel three miles out in the county, and why a figure taken off a national map is not a figure at all. It also cuts the other way: it is the same reason a barndominium shell that a city plan reviewer would question can be built without argument on unincorporated ground.

Could a fire district end up regulating my build instead?

Not for new construction here. Five fire protection districts serve the county — Southwest Buchanan County, South Central Buchanan County, Easton, DeKalb and San Antonio — and none of them publishes an adopted building or residential code. The statute settles it regardless. RSMo 321.228 defines a residential construction regulatory system to include any county ordinance pertaining to residential construction and any permitting programme relating to it, which is precisely what the county's Zoning Order and building permit are. Where a county has one, the section provides that fire protection districts wholly or partly inside it are without power, authority or privilege to enforce or implement one, and any they adopt is advisory only. The districts keep final authority over hydrant location, specification and flow rates and over fire lanes, and may inspect the alteration, enlargement, replacement or repair of a one- or two-family dwelling — not new construction — and may not charge for either. A district adopting a fire prevention code is a different matter and is lawful anywhere; that is not the same as running a building department.

What should I actually worry about in the ground here?

Silt and water, not rock. The soil survey of Buchanan County covers 265,255 acres and puts 127,961 of them on loess — wind-blown silt — with the two largest components, Knox and Marshall, running 61 to 73.5 percent silt and under 6 percent sand through the whole profile to depths of 150 to 200 centimetres. Bedrock within twenty inches shows up on only about 2.5 percent of the survey area, so the shallow-rock problem barely exists. What replaces it is a deep, fine-grained soil that holds its slope naturally in bluff faces and behaves very differently once wet, on ground where Knox is mapped at slopes from 2 to 35 percent. Add flooding — about 40,600 component-weighted acres are rated occasionally flooded and 11,300 frequently — and a Missouri River valley with poorly drained bottomland soils sitting at a water table right at the surface. The county has no code that will require a soil investigation before you pour, which is the argument for having one done and for a Missouri-licensed professional engineer sealing the foundation design on a large slab. And test for radon: the county sits in EPA Zone 1, the highest of three.

How long does a county permit take and what does it cost?

The Zoning Officer must act on a building permit application within thirty days of filing; if the application does not meet the Order's requirements, or thirty days pass without a decision, the applicant is notified and may appeal to the Board of Zoning Adjustment. The fees are published in § 805 of the Zoning Order. A single-family dwelling is fifteen cents per square foot of finished living space. A detached garage, shed or other accessory structure is fifteen cents per square foot with no cap; a farm or agricultural structure is fifty dollars up to five hundred square feet then ten cents per square foot, capped at five hundred dollars. A residential land disturbance permit is one hundred dollars. A conditional use permit for a dwelling, or a rezoning to a residential district, is three hundred and fifty dollars plus the cost of notifying surrounding owners and the legal advertising. Building first and applying afterwards doubles the permit fee. Permits are posted on site, displayed for thirty days after completion, and expire after a year unless extended.

Building in Buchanan County?

Start with the plan. Tell us what you want to build and we will draw it, then confirm which office issues the permit for your parcel, what it will let you put there, and what wind load it has to meet. That conversation costs nothing.

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