Boone County County-adopted code, county inspection

Barndominium Builders in Boone County, MO

Boone County is one of a small group of Missouri counties that both may have a building code and actually has one, and that single fact changes almost everything about building here. Classification is the gate: RSMo 48.020 sets a county's class by assessed valuation rather than population, the Missouri Association of Counties lists Boone in Class 1, and the State Tax Commission's 2024 report puts the county's total assessed valuation at $3,841,367,206. First classification is what RSMo 64.170 requires before a county commission may control construction and issue building permits. Boone County has used that power since 1985, began inspecting in March 1986 under the old BOCA codes, and now runs on the 2015 International Codes and the 2014 National Electrical Code, adopted by Commission Order 149-2017 on 23 March 2017 after three public hearings and effective 1 April 2017. That order repealed every previous version of the Boone County Building Code, which is why the 2012 addendums that are still posted on the county's website are history rather than law. Resource Management inspects everywhere in the county outside the city limits of Columbia, and the county fills in its own IRC Table R301.2(1): 20 lbs/sq. ft. ground snow, 115 mph wind, seismic design category B, severe weathering, a 30-inch frost line, termite moderate to heavy, decay slight to moderate, a winter design temperature of +4 degrees Fahrenheit, no ice barrier underlayment, an air freezing index of 0 to 1,000 and a mean annual temperature of 55 degrees. It also deletes IRC R403.3 outright, so a frost-protected shallow foundation is not an available route to that 30 inches here. The land question has its own answer. The USDA counted 1,120 farms working 196,763 acres in 2022 at a 176-acre average, and 43 percent of those farms are between 10 and 49 acres, which is precisely the tract a shop-and-house buyer is shopping for. That number collides with the zoning: in the A-1 Agriculture district a single-family dwelling needs a lot of at least 10 acres unless the parcel is a lot of record from before 27 December 1973, while A-2 drops to two and a half acres and A-R to half an acre. The ground under all of it is two different worlds. The Menfro series, formed in six to twenty feet of loess, has its national type location in this county about a mile and a half southeast of Wilton, and the level uplands to the north carry the full central-claypan suite instead. West and south of Columbia the county is karst: it publishes over 418 sinkholes, names three sinkhole areas in its zoning regulations by section, township and range, and requires wastewater systems in them to be designed and inspected by a registered professional engineer.

Boone County at a glance

County: Boone County
Population: 192,154
ZIP codes: 65010, 65039, 65201, 65202, 65203, 65240, 65255, 65256, 65279, 65284
Site visits: Same-week site visits across the unincorporated county, from Sturgeon and Centralia in the north through Hallsville, Harrisburg and Midway, west to Rocheport and Huntsdale above the river, and south through Pierpont and Hartsburg to Ashland and the Cole County line

Start your project

Building conditions in Boone 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 Boone 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 2012 addendums are repealed — Boone County has run on the 2015 codes since 1 April 2017

The certified copy of the order says it in one line: 'All previous versions of the Boone County Building Code are repealed on the effective date of this Commission Order.' That order is Commission Order 149-2017. The County Commission took it up on 23 March 2017, after public hearings on 23 February, 2 March and 7 March advertised in both Columbia newspapers and posted at the Government Center and at Centralia, Hallsville and Ashland city halls, on the recommendation of the Boone County Building Code Commission. It adopted the 2015 International Building Code, the 2015 International Residential Code, the 2015 International Plumbing Code, the 2015 International Mechanical Code, the 2015 International Fuel Gas Code, the 2015 International Existing Building Code, the 2015 International Energy Conservation Code and the 2014 National Electrical Code, all as amended and including appendices and referenced standards. The effective date is 1 April 2017 and the county's own building-inspections page repeats it: 'Boone County adopted 2015 International Codes which will be effective April 1, 2017. All permits issued on and after that date will be subject to the 2015 codes.' The instrument it replaced was Commission Order 140-2014, effective 2 April 2014, which had adopted the 2012 International Codes and the 2011 NEC. Anyone still quoting a 2012 addendum for Boone County is quoting an ordinance that has been dead for over nine years. The trap is easy to fall into, because the 2006, 2009 and 2012 addendum PDFs are all still linked from the same county page as history.

Boone County Commission, certified copy of order (Commission Order 149-2017), 23 March 2017, effective 1 April 2017, attested by the Clerk of the County Commission and bound as the front matter of 'Boone County Resource Management 2015 International Code Addendums, Effective Date 4/1/2017'; the same order is filed in the County Clerk's commission-order file for 23 March 2017. Superseded instrument: Commission Order 140-2014, printed on the '2012 International Code Addendums, Effective Date 4/2/2014'. Both addendum PDFs downloaded from boonemo.gov and read as extracted PDF text 8 September 2026, together with the Resource Management Building Inspections page and Regulations index, both read 8 September 2026

The county's whole Table R301.2(1) — and the one row in it that moved

Boone County fills in the residential code's design-criteria table itself, and here is all of it as adopted in 2017: ground snow load 20 lbs/sq. ft.; wind speed 115; topographic effects No; seismic design category B; weathering Yes, Severe; frost line depth Yes, 30 inches; termite Moderate to Heavy; decay Slight to Moderate; winter design temperature +4 degrees Fahrenheit; ice barrier underlayment required No; flood hazards 2 June 1983 as the date of original adoption of flood regulations and 17 March 2011 as the Flood Insurance Rate Map date; air freezing index 0 to 1,000; mean annual temperature 55 degrees Fahrenheit. The county's IBC addendum states the same 30 inches twice more, at 1809.5 and at 1801.2, alongside a presumptive allowable foundation bearing pressure of 1,500 psf. Now set that against the table it replaced. The 2012 addendums printed every single one of those values identically except one: wind speed 90 instead of 115. Nothing about the county changed. The residential code changed, from nominal design wind speeds to ultimate ones, and the county's number was restated in the new convention. This is the cleanest illustration available of why a wind speed is meaningless without its code edition attached, and it happens inside one county rather than between two. One more amendment belongs with the frost line: Boone County deletes IRC R403.3, frost-protected shallow foundations, in its entirety, so the 30 inches is not negotiable by that route.

Boone County Resource Management, 2015 International Code Addendums, IRC-2015 section, 'Table R301.2(1) - The following values shall be inserted into Table R301.2(1)', plus the R403.3 deletion in the same section and IBC-2015 sections 1604.1, 1801.2 and 1809.5; compared line by line against the 2012 International Code Addendums, IRC-2012 Table R301.2(1). Both PDFs downloaded from boonemo.gov and read as extracted text 8 September 2026

Ten acres for a house in A-1 — and a shop on five acres with no house at all

The Boone County Zoning Regulations, last revised 31 March 2026, permit a single-family dwelling in the A-1 Agriculture district only on a lot of at least 10 acres, or on a lot of record recorded before 27 December 1973. A-2 Agriculture allows one on two and a half acres, A-R Agriculture-Residential on half an acre, and R-S on 4,000 square feet. That 10-acre threshold sits directly across the most common tract size in the county: the 2022 agricultural census counted 482 farms between 10 and 49 acres, 43 percent of all 1,120 farms, against 351 between 50 and 179 acres and only 67 under 10 acres. Two provisions in Section 7 matter enormously to anyone planning a shop and a house. Section 7.1.5.2 allows a legally created parcel of five acres or more to carry a single accessory personal storage structure with no primary structure on the parcel at all, provided it is not used for any commercial purpose including a home occupation — so the building can go up before the house on a big enough tract. On a parcel under five acres, Section 7.1.5.1 says the opposite: no accessory building may be constructed until construction of the main building has actually commenced. Section 7.1.5.4 then closes the obvious loop, providing that accessory buildings may not be used for dwelling purposes except as a permitted accessory dwelling, which Section 7.1.3 caps at 75 percent of the primary dwelling's floor area or 1,500 square feet, whichever is less, with a minimum ten-foot separation unless the two share a common wall. The building code adds its own ceiling: an accessory structure is defined as one not greater than 3,000 square feet, not more than three storeys or 24 feet in height, and it 'shall not exceed the height of the main structure.' A shop taller than the house is not an accessory structure here.

Zoning Regulations, Boone County, Missouri, adopted 27 December 1973 and last revised 31 March 2026, Sections 5.A(1), 5.A(3), 5.A(5), 5.A(7), 7.1.3, 7.1.5, 9.A, 10.A and 11.A, downloaded from boonemo.gov and read as extracted PDF text 8 September 2026; accessory-structure definition from the 2015 International Code Addendums, IRC-2015 R202; farm-size distribution from USDA NASS 2022 Census of Agriculture, Boone County, Missouri county profile (cp29019), downloaded and read 8 September 2026

The farm exemption is twenty acres and seventy-five feet — and it does not cover the house

Boone County writes its agricultural carve-out into the building code itself, at section 0.2.1 of the addendums, and the wording is specific enough to plan around: the code shall not be exercised so as to impose regulations or require permits for the erection, maintenance, repair, alteration or extension of farm buildings or farm structures further than 75 feet from a dwelling, provided the buildings are on tracts of 20 acres or more and are used exclusively for agricultural purposes. Then the next sentence: 'Farm dwellings shall conform to the provisions of this code as herein provided.' Three conditions and one exclusion, and the exclusion is the whole point for this building type. The residential code's own scope amendment says the same thing from the other side, noting that its provisions do not apply to agricultural buildings and that where an agricultural building does require a permit it must be designed and built to the International Building Code or another standard approved by the building official. The county's agricultural-structures handout adds the sentence that catches most people: 'A permit is required to install electric in ANY building.' Boone County also defines agricultural activity narrowly, as cultivating the soil, producing crops and raising animals for food or fibre including horticulture, beekeeping, aquaculture, silviculture and forestry, and states expressly that raising and keeping horses for any purpose other than the production of food and fibre is not agricultural activity. What does need a permit is published as a list: any structure larger than 160 square feet, any commercial or industrial building, any construction involving structural, electrical, plumbing, heating and air or insulation work, and then by name garages, carports, sheds, barns, work shops, 'Barn/Shop', greenhouses, swimming pools, fences over 12 feet and retaining walls over four feet.

Boone County Resource Management, 2015 International Code Addendums, sections 0.2.1 (farm structure exemption), 0.2.2, 0.2.3 and R101.2 scope note, downloaded from boonemo.gov and read 8 September 2026; Boone County Planning and Building Inspection handouts 'Agricultural Structures' (Ag-Structures.pdf) and 'Types of construction requiring a building permit' (Buildings_Requiring_Permit.pdf), both linked from the county's Building Inspections page and downloaded 8 September 2026; 'Boone County, Missouri Guide to Construction Permits', Resource Management, downloaded 8 September 2026

Metal siding, roof pitch, eaves, design review, minimum house size: Boone County regulates none of them

This is worth stating plainly because some Missouri jurisdictions do regulate all five, and a buyer choosing between counties has no easy way to find out. The Boone County Zoning Regulations as revised 31 March 2026 were read through for exterior material restrictions, minimum roof pitch, minimum eave projection, architectural or appearance review and minimum dwelling floor area. There are none for a site-built single-family dwelling. Section 5 sets uses, Section 9 sets a 35-foot height limit for non-farm buildings in the agricultural and residential districts, Section 10 sets yards and Section 11 sets lot areas, and none of them says anything about what a wall or roof may be made of. The Character Preservation Overlay District at Section 23 is the only appearance-based instrument in the ordinance, and its standards reach screening, outdoor lighting, billboards and signage on commercially and industrially zoned property, not the cladding of a house. The building code addendums add no material or pitch restriction either. The only minimum floor area anywhere in the ordinance is 650 square feet, and it applies to a manufactured home under Section 4.A(9), not to a site-built dwelling; the same subsection requires under-skirting within 90 days, tie-downs to 15 pounds per square foot within 30 days, and provides that a site-built addition to a single-wide unit cannot be counted toward the 1,000 square feet that would reclassify it as a modular building. A steel-clad, low-pitch, short-eave building is a lawful house in unincorporated Boone County. The constraints here are lot size, setbacks, height and the wastewater answer, not appearance.

Zoning Regulations, Boone County, Missouri, last revised 31 March 2026, read in full for exterior-material, roof-pitch, eave, design-review and floor-area provisions, with Sections 4.A(9), 5, 7, 9, 10, 11 and 23.6 checked specifically; and Boone County Resource Management 2015 International Code Addendums, IRC-2015 and IBC-2015 sections. Both downloaded from boonemo.gov and read as extracted PDF text 8 September 2026

The fire district runs a fire code, not a building code — and it is the district that says so

The Boone County Fire Protection District is one of the largest in Missouri, with sixteen stations from Rocheport and Harrisburg to Centralia, Sturgeon and Midway, and it covers most of the unincorporated county. It publishes its own division of labour, and it lines up exactly with the statute. The district states that it 'operates under the 2018 International Fire Code with local amendments adopted by the district's Board of Directors', that its Life Safety Division holds 'fire-code jurisdiction for commercial properties and residential properties larger than a duplex within district boundaries', and — in its own words — that 'Single-family and duplex building-code jurisdiction belongs to Boone County.' It routes new construction outside Columbia to the county's building-permit process, has the county's Inspections Division schedule construction inspections, and joins those inspections where a fire-code requirement is involved. What it keeps is fire-department access, fire-department connections, water supply and hydrants, and a county handout confirms that hydrants with the necessary fire flows and pressures must be installed and operating before the district will approve occupancy. That is precisely the shape RSMo 321.228 prescribes. Where a county 'adopts or has adopted, implements, and enforces a residential construction regulatory system', a fire protection district inside it 'shall be without power, authority, or privilege to enforce or implement a residential construction regulatory system' there, and any such system a district adopts 'shall be treated as advisory only'; districts keep final regulatory authority over the location and specifications of fire hydrants, hydrant flow rates and fire lanes, may inspect the alteration, enlargement, replacement or repair of a detached one- or two-family dwelling, and shall not charge a fee for either. Southern Boone County Fire Protection District, around Ashland, works the same way, reviewing plans and inspecting under the International Fire Code with its fee collected on its behalf by the county. Which district covers a given address is worth asking rather than assuming; the county's own list also names Centralia and Columbia fire departments.

Boone County Fire Protection District, 'Life Safety Division' page at bcfdmo.com, rendered and read 8 September 2026 (host control-tested the same day: a bogus path returns HTTP 404 with the title '404 Error: Page Not Found'); RSMo 321.228, 'Residential construction regulatory system, preemption of law by local governmental body over fire protection district, when, exceptions', effective 28 August 2012 (L. 2012 H.B. 1647 merged with S.B. 769), rendered from revisor.mo.gov 8 September 2026; Boone County Planning and Building Inspection handouts 'Information regarding fire district requirements' (Fire_District_Firehydrants.pdf) and 'Southern Boone County Fire Protection District requires fees' (SBC_Fire_Protection_District_Fees.pdf), both downloaded from boonemo.gov 8 September 2026

Also worth knowing before you build in Boone County

Septic is a county ordinance here, and the footing inspection waits on it: The Missouri Department of Health and Senior Services county selector returns Boone County to Boone County Resource Management with Authority Type: Ordinance, at 801 E. Walnut Room 315 in Columbia, with the department's own note that 'This county has their own Onsite Wastewater Ordinance and may have additional requirements beyond the state minimum construction standards.' The county adopted its on-site sewage ordinance in 1993; enforcement sat with City of Columbia and Boone County Public Health and Human Services for years and transferred to Resource Management effective 28 June 2022. In practice the process runs like this: a soil evaluation by a certified soil scientist first, then a permit application carrying the soils morphology report, then a pre-site inspection scheduled for the next business day, then installation by an installer from the county's certified list with no backfilling until the final inspection. Alternative systems must be designed by an engineer. If a new home is being permitted at the same time, the wastewater application is folded into the building permit rather than filed separately. The sequencing rule is the one that catches schedules: the county states that where an on-site system is proposed, the wastewater permit must be approved and the site inspection performed before any other inspection is scheduled, and that this includes footing inspections, which will not be scheduled on the same day as the wastewater pre-site inspection. Note also what an ordinance authority means for the three-acre argument. RSMo 701.031 excludes some single-family lots of three acres or more from the state programme, but RSMo 701.047 lets a county ordinance reach the same parcel, and Boone County's published instructions describe a permit requirement for anyone constructing a new building with an on-site sewage system without stating an acreage exemption. Ask Resource Management about the specific parcel rather than working from the state threshold.
Over 418 sinkholes, three named sinkhole areas, and a 3,000 square foot land-disturbance trigger: Boone County is karst country west and south of Columbia. The county publishes the count itself: 'There are over 418 sinkholes in Boone County; most of which are located south of I-70 near Rocheport and Pierpont', over a network of caves and losing streams, with more than 43 losing stream segments along Gans Creek, Fox Hollow Branch, Bonne Femme Creek, Slate Creek, Sinking Creek, Jemerson Creek, Bass Creek and their tributaries. Two consequences are written into county law. Section 12 of the Zoning Regulations names three sinkhole areas by section, township and range — the Pierpont area, the Rocheport and Huntsdale area, and the Midway area — and provides that where public or community sewer is not available in them, sewage disposal systems shall be designed and installed to plans prepared by a registered professional engineer, inspected by or under the supervision of one, and certified by that engineer in a letter to the Director stating the system was properly designed for a sinkhole area. Second, the stormwater ordinance drops the land-disturbance permit threshold from one acre to 3,000 square feet where runoff discharges to a groundwater recharge feature such as a sinkhole or cave, or where the site is within 1,000 feet of or drains to an identified losing stream. On a rural building site those two rules can convert a routine driveway-and-pad job into an engineered wastewater design and a stormwater pollution prevention plan, and both questions are answerable from a parcel map before an offer is made.
The state soil's type location is in this county, and the claypan is in it too: Boone County straddles two entirely different foundation problems. Along the Missouri River hills the ground is loess, and the USDA's Official Series Description for the Menfro series — Missouri's state soil — places its national type location in Boone County, about a mile and a half southeast of Wilton on the Hartsburg quadrangle. Menfro formed in loess deposits 'ranging from 6 to 20 feet or more thick' on upland ridgetops, backslopes and benches, with slope gradients from 2 to 60 percent and a solum typically 50 to 70 inches deep. That is deep, well-drained, fine-textured soil with no rock in the way and a lot of slope to think about. On the level uplands north and east it is a different soil entirely: Boone is one of only thirteen Missouri counties carrying the full central-claypan suite as major map-unit components, and the claypan series behave in the opposite way — the Mexico series is classified as a Vertic Epiaqualf, which puts the shrink-swell clay in the taxonomy itself, with the top of the claypan 7 to 18 inches down, very slow permeability and a perched water table between half a foot and a foot and a half from December to May in most years. A slab detail that suits a Menfro ridge above the river is not the detail for a claypan flat twenty miles north, and neither is a guess. The county's own IBC amendment sets a presumptive allowable bearing pressure of 1,500 psf and waives a geotechnical investigation only for one-storey buildings of 2,500 square feet or less in risk categories 1 and 2, which is a reasonable place to start the conversation and not a substitute for a soil boring.
Land in Boone County: 1,120 farms, and 43 percent of them under 50 acres: The 2022 Census of Agriculture counted 1,120 farms in Boone County working 196,763 acres at an average of 176 acres, down 5 percent in land and 8 percent in farm count since 2017. The use split is 119,577 acres of cropland, 33,674 acres of woodland, 32,044 acres of pastureland and 11,468 acres of other land, with 4,792 acres irrigated. The size distribution is the number that matters to a barndominium buyer: 67 farms of 1 to 9 acres, 482 of 10 to 49 acres, 351 of 50 to 179 acres, 140 of 180 to 499 acres, 45 of 500 to 999 acres and 35 of 1,000 acres or more. Forty-three percent of the county's farms are in that 10-to-49-acre band, which is exactly the tract this building type is usually bought for, and it is also the band that sits below the A-1 district's 10-acre minimum for a dwelling on one side and above the A-2 district's two and a half acres on the other. The practical reading is that the zoning district on a parcel matters as much as its acreage, and both are worth checking on the county's zoning map before an offer rather than after.

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 Boone County

All nine services are available in Boone 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.

See all nine services

What a build looks like

Three stages every Boone 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 Boone County. Tell us what you want to build and we will draw it to them.

Start your project

Where we build around Boone County

Boone 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 Boone 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 Boone County allows.

Barndominium Cost Guide

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

Read it

Is It Legal in Missouri?

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.

Read it

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.

Columbia

Boone County

Callaway County

Building in Boone County: common questions

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

Start your project

Does Boone County actually inspect a house built out in the country, or is that only inside Columbia?

It inspects. Boone County Resource Management states that its Inspections Division 'is responsible for building inspections in Boone County, Missouri, outside the city limits of Columbia', and that anyone inside the city should contact the city's office instead. The county has had building codes since 1985 and has run an inspection programme since March 1986. It currently enforces the 2015 International Building, Residential, Plumbing, Mechanical, Fuel Gas, Existing Building and Energy Conservation Codes together with the 2014 National Electrical Code, adopted by Commission Order 149-2017 and effective 1 April 2017. A building permit is required for any structure larger than 160 square feet and for any work involving structure, electrical, plumbing, heating and air or insulation, and that list expressly names barns, work shops, garages, carports, sheds and 'Barn/Shop'. Certificates of occupancy are issued by the county and take about three business days to process. So the honest answer for unincorporated Boone County is the opposite of the one that applies in most Missouri counties: there is a code, there is a building official, and there is a certificate at the end of it.

I have been told Boone County's frost line is 30 inches and its wind speed is 90 mph. Is that right?

Half right, and the half that is wrong is the half people usually quote. The frost line is 30 inches and that has not moved: the county inserts 'Frost Line Depth - Yes; 30 inches' into IRC Table R301.2(1) in its current 2015 addendums, and repeats the figure at IBC 1809.5 and 1801.2. The wind speed is 115 mph, not 90. Ninety was the figure in the 2012 addendums, adopted by Commission Order 140-2014, and those were repealed on 1 April 2017 when the 2015 codes took effect. What makes this worth understanding rather than just correcting is that every other value in the two tables is identical — 20 psf ground snow, seismic design category B, severe weathering, the same 30-inch frost line, termite moderate to heavy, decay slight to moderate, a +4 degree winter design temperature, an air freezing index of 0 to 1,000 and a 55 degree mean annual temperature. Only the wind number changed, and it changed because the residential code moved from nominal design wind speeds to ultimate ones. Boone County did not get windier between 2014 and 2017. If a supplier is comparing a 90 to a 115 as though one place were calmer than another, ask which code edition each figure came from.

Can I put up the shop first and build the house later?

On five acres or more, yes, and the county writes it down. Section 7.1.5.2 of the Zoning Regulations allows a legally created parcel of five acres or larger to have a single accessory personal storage structure without a primary structure on the parcel, as long as it is not used for any commercial purpose including a home occupation. Below five acres the rule reverses: Section 7.1.5.1 provides that no accessory building may be constructed on a lot until construction of the main building has actually commenced, and that no accessory building may be used unless the main building is also in use. Two limits go with this. Accessory buildings may not be used for dwelling purposes except as a permitted accessory dwelling, which is capped at 75 percent of the primary dwelling's floor area or 1,500 square feet, whichever is less. And the building code defines an accessory structure as not greater than 3,000 square feet, not more than three storeys or 24 feet high, and specifically not exceeding the height of the main structure — so a tall shop bay beside a single-storey house is a design question to settle with the building official before anything is ordered. Whatever the sequence, the building itself needs a permit: anything over 160 square feet does, and so does any electrical work in any building at all.

Are there any rules in Boone County against metal siding or a low roof pitch?

No. The Boone County Zoning Regulations as revised on 31 March 2026 contain no exterior material restriction, no minimum roof pitch, no minimum eave projection, no architectural or design review for a dwelling, and no minimum floor area for a site-built house. Sections 9, 10 and 11 regulate height, yards and lot area and say nothing about what a wall or roof is made of, and the Character Preservation Overlay District's appearance standards at Section 23.6 reach screening, lighting, billboards and signage on commercial and industrial property rather than the cladding of a house. The 2015 building code addendums add nothing on materials or pitch either. The only floor-area minimum in the ordinance is 650 square feet, and it applies to a manufactured home under Section 4.A(9), not to a site-built dwelling. That answer is specific to unincorporated Boone County and does not travel: some Missouri jurisdictions do prohibit corrugated or flat sheet-metal exteriors and do set a minimum pitch, and a few set a minimum dwelling size, so the same question has to be asked again inside any city's limits.

My land is in the fire district. Does the fire district have to approve my house too?

Not for the building code, and the district says so itself. The Boone County Fire Protection District publishes that it 'operates under the 2018 International Fire Code with local amendments adopted by the district's Board of Directors', that its fire-code jurisdiction covers commercial property and residential property larger than a duplex inside its boundaries, and that 'Single-family and duplex building-code jurisdiction belongs to Boone County.' It sends new construction outside Columbia to the county's permit process and has the county's inspectors schedule the work, joining an inspection where a fire-code item is involved. What the district does keep is the water side: fire-department access, connections, fire flow and hydrants, and a county handout confirms hydrants with the necessary flows and pressures must be installed and operating before the district signs off on occupancy. That split is what RSMo 321.228 requires. Where a county adopts, implements and enforces a residential construction regulatory system, a fire protection district inside it is 'without power, authority, or privilege to enforce or implement' one, and anything of that kind the district adopts is advisory only — while the district keeps final authority over hydrant location and specification, hydrant flow rates and fire lanes, may inspect alterations, enlargements, replacements and repairs of a one- or two-family dwelling, and may not charge a fee for either. Boone County is a clean example of the statute doing exactly what it says. Which district covers a particular address is still worth confirming, because Southern Boone County Fire Protection District covers the Ashland end of the county and Centralia and Columbia run their own departments.

How much land do I actually need to build a house in Boone County?

It depends entirely on the zoning district, and the spread is wide. In A-1 Agriculture a single-family dwelling needs a lot of at least 10 acres, unless the parcel is a lot of record recorded before 27 December 1973. A-2 Agriculture allows one on two and a half acres. A-R Agriculture-Residential allows one on half an acre, 21,780 square feet. R-S Single-Family Residential allows one on 4,000 square feet. Setbacks follow the district too: 50 feet front, 50 feet rear and 15 feet side in A-1 and A-2, and 25 feet front, 20 feet rear and 5 feet side in A-R and the residential districts. There is one more acreage line worth knowing before an offer: Section 4.A(4) makes any division of land subject to the Subdivision Regulations if the resulting lots or tracts contain less than twenty acres, which turns a casual split of a family farm into a platting exercise. And the building code has its own twenty-acre line for a different purpose — the farm-structure exemption at section 0.2.1 only reaches buildings on tracts of 20 acres or more, more than 75 feet from a dwelling, used exclusively for agricultural purposes, and it expressly does not reach the dwelling itself. Two different twenty-acre rules in two different instruments, doing two different jobs.

What is the wastewater process, and does the three-acre rule get me out of it?

Do not plan on the three-acre rule. The Missouri Department of Health and Senior Services lists Boone County under Authority Type: Ordinance, with Boone County Resource Management as the permitting agency, and adds that the county has its own on-site wastewater ordinance and may have requirements beyond the state minimum construction standards. RSMo 701.031 excludes some single-family lots of three acres or more from the state programme, but RSMo 701.047 allows a county ordinance to reach the same parcel, so the state threshold is a floor rather than an answer. Boone County adopted its ordinance in 1993 and moved enforcement to Resource Management on 28 June 2022. The sequence is a soil evaluation by a certified soil scientist, then the permit application with the soils morphology report attached, then a pre-site inspection, then installation by an installer from the county's certified list with no backfilling before the final inspection. Alternative systems have to be designed by an engineer, and in the Pierpont, Rocheport-Huntsdale and Midway sinkhole areas named in Section 12 of the zoning regulations, any system has to be designed and inspected by a registered professional engineer who then certifies it in writing to the Director. One scheduling detail decides your build calendar: where an on-site system is proposed, the wastewater permit has to be approved and the site inspection done before any other inspection is scheduled, footing inspections included, and the two cannot be booked for the same day.

Building in Boone 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.

Start your project