Platte County County-adopted code, county inspection

Barndominium Builders in Platte County, MO

Platte County is 419.823 square miles of deep wind-blown soil above the Missouri River, and it holds the best land-to-access ratio in the Kansas City metro: 485 farms working 147,941 acres at a 305-acre average, with Kansas City International Airport and Interstate 29 running straight up the middle of it. It is also a first-classification county that has actually used the power that classification gives it. Under RSMo 64.170 only first- and second-classification counties may adopt a building code at all, and Platte County has one — the 2018 International Residential Code and a full set of companion codes, with a Planning and Zoning Department that reviews plans and runs footing, pre-backfill, ground-rough, rough-in and final inspections. That is the opposite of the rural-Missouri default, and it is the first thing a buyer here needs to know. The second is where it stops. A county building code adopted under RSMo 64.170 to 64.200 applies only to unincorporated territory, and Platte County is unusually incorporated: of its 113,207 residents, 55,477 live inside the Kansas City city limits and another 27,127 live in eighteen other municipalities, leaving 30,603 in the unincorporated balance the county's own code and zoning actually reach. So the practical question on any Platte County parcel is not whether a code applies — one almost always does — but which authority's code it is, and the answer changes at a city line rather than at the county line.

Platte County at a glance

County: Platte County
Population: 113,207
ZIP codes: 64018, 64028, 64079, 64089, 64092, 64098, 64150, 64151, 64152, 64153, 64154, 64163, 64164, 64439, 64440, 64444, 64484, 64492
Site visits: Same-week site visits across the county — the river bluffs at Riverside and Parkville, the ridge country around Platte City and Weston, and the open ground north to Dearborn and Camden Point

Start your project

Building conditions in Platte 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 Platte 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 has a building code, and it stops at every city line

Platte County is one of the minority of Missouri counties that both may have a building code and does. RSMo 64.170 empowers only counties of the first and second classification to control construction and issue building permits, and Platte County is first classification. It has used that power: its Building Permit Packet lists the 2018 International Building, Residential, Plumbing, Mechanical, Fuel Gas, Energy Conservation and Swimming Pool and Spa Codes plus the 2017 National Electrical Code as adopted, with amendments to the IBC and IRC in County Commission Order No. 2019-CO-181, and the department runs footing, pre-backfill, ground rough, rough-in and final inspections. But RSMo 64.180 limits a code adopted under RSMo 64.170 to 64.200 to 'the unincorporated territory of the county', and Platte County is heavily incorporated. Of 113,207 residents in 2024, the Census Bureau puts 55,477 inside the Kansas City city limits, 8,980 in Parkville, 4,867 in Platte City, 4,498 in Riverside, 2,125 in Weatherby Lake, 1,837 in Weston and the rest across a dozen smaller places — leaving 30,603 in the unincorporated balance. The county's building department, its Zoning Order and its subdivision rules reach that 30,603 and nobody else.

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, and RSMo 64.180, effective 28 Aug 2001, both rendered from revisor.mo.gov 6 September 2026; Platte County Planning and Zoning, Building Permit Packet, co.platte.mo.us, retrieved 6 September 2026; U.S. Census Bureau Vintage 2024 Subcounty Population Estimates, Missouri file sub-est2024_29.csv, SUMLEV 157 place-part records and the 'Balance of Platte County' record, fetched from www2.census.gov 6 September 2026

This is loess country, and two-thirds of the county is built on it

Platte County sits in the Iowa and Missouri Deep Loess Hills — MLRA 107B in the USDA's national land-resource scheme — and loess, silt carried in on the wind off the Missouri River flood plain after the last glaciation, is the county's dominant parent material. The USDA soil survey of the county puts about 35 percent of it in the Sharpsburg-Higginsville-Sibley association, deep loess on wide ridgetops and side slopes, and about 31 percent in the Knox-Snead association, the deeply dissected narrow ridges and valleys next to the Missouri River flood plain. Two-thirds of Platte County, in other words, is wind-blown silt. The NRCS's current series descriptions put numbers on what that means for a foundation. Knox is 'very deep, well drained soils formed in loess' on 'strongly dissected hills and bluffs bordering the Missouri River Valley and its tributaries', slopes 2 to 35 percent, less than 5 percent sand anywhere in the profile. Sharpsburg is 'very deep, moderately well drained soils formed in loess', classified fine and smectitic — smectite being the clay mineral that shrinks and swells — carrying 36 to 42 percent clay through its particle-size control section. A silt with almost no sand in it and a smectitic clay subsoil are two different foundation problems on two parts of the same farm.

USDA Natural Resources Conservation Service, Official Series Descriptions for KNOX (rev. 09/2008), SHARPSBURG (rev. 11/2020) and SIBLEY (rev. 02/2003), soilseries.sc.egov.usda.gov, read 6 September 2026; association percentages and parent-material discussion from the USDA Soil Conservation Service, Soil Survey of Platte County, Missouri (1985), read as digitised text from the USDA-deposited scan in the National Agricultural Library soil survey collection, 6 September 2026

What Platte County actually publishes: 115 mph, 20 psf, termites moderate to heavy

The county states its own design criteria in the Building Permit Packet, in one sentence: 'The wind load for Platte County at this time is 115 mph, snow load is 20 lbs, per the 2018 International Building Codes.' The next line gives Termite Infestation Probability as Moderate to Heavy. That is the whole of it. The packet prints no frost line depth, no seismic design category, no air freezing index and no winter design temperature, and there is no state figure standing behind it — Missouri has no statewide residential code and no statewide design table. So a builder working here has the county's wind and snow numbers in writing and has to get the footing depth from the building official, which is a better answer than a figure lifted off a national map and a far better answer than a neighbouring jurisdiction's number.

Platte County Planning and Zoning, Building Permit Packet, section headed GENERAL INFORMATION, co.platte.mo.us, retrieved 6 September 2026

In the AG district your shop needs 100 feet of side yard and your house needs 30

The Platte County Zoning Order of 1990 divides the county into nineteen districts, and three of them are where rural acreage sits. In AG Agricultural, each dwelling and its accessory buildings need 40 acres of lot area, 400 feet of lot width at the front building line and 100 feet of street frontage; RE Rural Estates needs 5 acres on the same 400-foot width; R-80 Rural Single-Family needs 80,000 square feet, about 1.84 acres, on 200 feet. Height is capped at 35 feet in all three and buildings may not cover more than a quarter of the lot. The setback lines are where a shop-house design gets decided. Section 400.130(D) gives AG a 100-foot front yard and a 30-foot side yard for the dwelling on an interior lot, then sets the side yard for 'accessory buildings other than dwellings' at not less than 100 feet from every exterior and interior side lot line; the rear yard is 100 feet for the dwelling and 50 feet for an unattached accessory building. The same clause in RE and R-80 lets an unattached building accessory to a dwelling sit 15 feet off the side line. On a 40-acre AG tract that is workable; on a narrow one it decides where the building goes. The Order also allows, as a special use, one additional detached single-family dwelling on a tract of 40 acres or more for the principal owner's family or employees.

Platte County Zoning Order of 1990, as amended (Title IV Land Use, Chapter 400 Zoning Regulations, updated through October 17, 2022), §§ 400.080, 400.130, 400.140, 400.150, published by Platte County at co.platte.mo.us, read 6 September 2026

Septic here runs on a county ordinance, not the state programme

Missouri's Department of Health and Senior Services resolves every county to one of three on-site wastewater authority types, and for Platte County it names the Platte County Health Department at 212 Marshall Rd, Platte City, (816) 858-2412, with Authority Type recorded as 'Ordinance' — and this alert against it: 'This county has their own Onsite Wastewater Ordinance and may have additional requirements beyond the state minimum construction standards.' That matters more than it sounds. RSMo 701.031 excludes the owner of a single-family residence lot of three acres or more from the state on-site sewage provisions — the exemption most rural Missouri buyers have heard about — but RSMo 701.047 preserves a city's or county's power to adopt more restrictive standards, and Platte County has done exactly that. The county's own building permit checklist closes the loop from the other side: a one- or two-family dwelling permit requires a septic permit from the Health Department, or a sewer permit from the Platte County Regional Sewer District or Timber Creek Sewer Company, plus a letter from the applicable water district confirming water is available. DHSS adds one more wrinkle that is the same wrinkle as the building code: where work is inside an incorporated area, the local permitting authority may defer the permit back to DHSS.

Missouri Department of Health and Senior Services, OWTS Construction Permit Process county authority list, health.mo.gov, Platte County record read 6 September 2026; RSMo 701.031 (L. 1986 H.B. 1101 § 4; A.L. 1994; A.L. 1999; A.L. 2004; A.L. 2005 H.B. 617), effective 28 Aug 2005, and RSMo 701.047; Platte County Planning and Zoning, Building Permit Packet, single family dwelling / two-family dwellings permit checklist, retrieved 6 September 2026

A barn needs a permit here, and it is fifty dollars

Platte County's published fee schedule has a line item headed BARN / GARAGE / SHED PERMIT, which settles the question people arrive with. A barn or garage costs $50.00 for the first 500 square feet or portion thereof plus $0.10 for each additional square foot; a shed is $50.00 plus $0.05. A one- or two-family dwelling is $200.00 for the first 500 square feet or part thereof plus $0.25 for each additional square foot up to 1,400 square feet, and $300.00 for the first 500 plus $0.35 for each additional square foot from 1,401 square feet up. A deck is $50.00, a swimming pool $75.00, an electrical or solar panel permit $50.00 each, a residential demolition $25.00. The county says an application 'shall be reviewed and acted upon within five (5) working days after the receipt of all the required information', and that no construction is allowed until the permit is issued — starting early doubles the fee under the county's amendments in County Commission Order No. 2019-CO-181, and can draw a stop work order as well. New residential and commercial permits expire two years from issue; permits for pole barns, detached garages, sheds, additions, remodels and solar expire in six months. Work must begin within 180 days and must not stop for more than 180.

Platte County Planning and Zoning, Building Permit Packet — fee lines under SINGLE FAMILY DWELLING/TWO-FAMILY DWELLINGS PERMIT, BARN / GARAGE / SHED PERMIT, DECK PERMIT, SWIMMING POOL PERMIT, ELECTRICAL PERMIT, SOLAR PANEL PERMIT and DEMOLITION PERMIT, and the sections headed EXPIRATION and PENALTY, co.platte.mo.us, retrieved 6 September 2026

Also worth knowing before you build in Platte County

485 farms, 147,941 acres, and a 305-acre average: The 2022 Census of Agriculture counts 485 farms in Platte County working 147,941 acres, averaging 305 acres apiece — against a Missouri average of 308 — on a county whose total land area the Census Bureau measures at 419.823 square miles. Of that farmed ground, 110,855 acres are cropland and 12,461 acres pastureland. The size distribution is what makes this a buildable market rather than a big-spread one: 154 of the 485 farms are between 10 and 49 acres and another 190 are between 50 and 179 acres, so two-thirds of the holdings in the county are already in the size band a house-and-shop build wants, inside a metro area. Land in farms fell only 1 percent since 2017 while the average farm size fell 8 percent — the county is subdividing rather than being paved.
The erosion rules are the loess showing through the ordinance: Read the county's construction rules next to its soils and the connection is obvious. A Land Disturbance Permit is required for any project disturbing one acre or more, excluding agricultural use, with a Sediment and Erosion Control Plan approved by the Planning and Zoning Director before it issues; the Sediment and Erosion Control Regulations at § 400.535 exist, in the Order's own words, 'to control soil Erosion on land that is undergoing Land Disturbance activities for non-agricultural uses and to prevent Sediment and soil Erosion from being transported onto adjacent property'. Then comes the clause that costs money on a hillside site: to get a temporary certificate of occupancy before ground cover is established, the owner must document an escrow account, held by a third party, in the amount of the cost to re-establish vegetation plus 50 percent, and control measures must stay in place until vegetation is back. And if a county inspector finds that ground adjacent to the lot has been disturbed by the permit holder — regardless of who owns it — vegetation must be re-established there too before an occupancy permit issues. On a soil with less than 5 percent sand in it, on slopes running to 35 percent, that is not boilerplate.
Weston is on the National Register — which restricts nothing by itself: The Weston Historic District, roughly bounded by Summit, Rock, Market and Ashley, was listed in the National Register of Historic Places on 21 August 1972, one of sixteen Platte County listings the Missouri State Historic Preservation Office records alongside the Platte County Courthouse, the McCormick Distillery, the Frederick Krause Mansion and the Waddell 'A' Truss Bridge at Parkville. What that listing does is widely misunderstood, and the Missouri SHPO answers it directly: the National Register is 'an honorary list', and 'State and federal governments do not place restrictions on private property listed in the National Register. Check with your local government to see if there are ordinances that concern historic properties.' The restriction, where one exists, is municipal — which is the same boundary that decides the building code. Weston is one of nineteen incorporated places wholly or partly inside Platte County, and inside any of them the county's own code and Zoning Order do not apply.
Around the airport, the county applies Kansas City's height rules: Kansas City International Airport sits inside the Kansas City portion of Platte County, and the county's Zoning Order does not write its own approach surfaces for it. Section 400.400 provides that the height of buildings and structures in areas surrounding the boundaries of Kansas City International Airport 'shall be governed by the regulations established by the City of Kansas City, Missouri, and adopted hereby by reference'. For airports without an established approach plan the Order sets its own sliding scale instead: within 10,000 lineal feet of the boundary, 15 feet at the edge, rising by 10 feet per 200 feet of distance for a runway under 3,950 feet, or 5 feet per 200 feet for a longer one, and 4 feet per 200 feet where the runway is designated an instrument runway. Since the districts a barndominium sits in cap height at 35 feet anyway, this bites on a tall shop or a grain leg rather than on the house.
The floodplain ordinance dates from 1986 and is folded into the zoning: Platte County has the Missouri River on two sides of it, and the Zoning Order handles that by reference rather than by rewriting it: § 400.490 provides that uses within the floodway overlay and floodway fringe overlay districts designated by the Federal Emergency Management Agency are subject to the Flood Plain Management Ordinance adopted by the Platte County Commission on 13 November 1986, adopted into the Order by reference. The county maintains its own flood information and Flood Insurance Rate Map pages through the Planning and Zoning Department, and a Flood Development application is one of the case types in the county's permit portal. On a bottomland parcel that instrument, not the building code, is the one that decides how high the finished floor sits.
The county licenses liquor, auctioneers and tow trucks — not builders: Platte County publishes an index of the licences it issues, and it runs: personal property tax, real estate tax, marriage licences, liquor licences, auctioneer licences, notary public licences, merchant and manufacturing licences, tow truck permits and concealed carry permits. There is no general contractor licence on it, no building contractor licence, and no county electrical, plumbing or mechanical licence. The building permit application procedure asks only that applications be presented by 'the owner or lessee, (or agent of either), architect, engineer or builder employed in connection with the proposed work' — there is no licence number to give. What the county does require is professional sealing on the drawings: a one- or two-family dwelling permit calls for a set of sealed drawings by an engineer licensed in the State of Missouri, a sealed truss design where trusses are used, and a site plan completed by a surveyor licensed in the State of Missouri. Missouri has no statewide general contractor or residential builder licence to hold either; the one statewide construction licence that exists is the electrical contractor licence under RSMo 324.900 to 324.945, and RSMo 324.920(4) makes even that optional where the political subdivision requires no local licence.
Every county Kansas City touches is EPA Radon Zone 1, and this is one: Only 11 of Missouri's 114 counties fall in EPA Radon Zone 1, the band with a predicted average indoor screening level above 4 pCi/L. Platte County is one of them, with Andrew, Atchison, Buchanan, Cass, Clay, Clinton, Holt, Iron, Jackson and Nodaway — the Kansas City metro and the state's northwest corner. EPA's own guidance is that the map should not be used to decide whether an individual home needs testing and that all homes should be tested regardless of zone, so the useful way to treat it is as a decision to make at slab or crawlspace stage, when passive sub-slab depressurisation costs very little, rather than as a retrofit later.
There is a family route through the lot-size rules: Zoning Order § 400.551 allows a Family Unit Subdivision in the AG, RE, R-80 and R-40 districts. Its design 'may provide for modification but not the elimination of yard, setback, road frontage, lot widths and lot area' — so it is the one mechanism in the Order that flexes the 40-acre AG minimum without a rezoning. The trade is a strict one: the aggregate density of the tract stays exactly what conventional development would have allowed, and residents 'must be immediate family members, including parents, children, siblings or grandchildren only', with a signed affidavit to that effect before approval. It follows the ordinary platting process, or the minor-subdivision platting process where it qualifies, and the Planning and Zoning Commission expressly reserves the right to refuse an application it finds insufficient.
The corrugated-metal prohibition sits in the business-park district, and a dwelling is not permitted there: Platte County's Zoning Order does contain an exterior-material prohibition, and where it sits is the whole of the point. It is § 400.280.F.9, in the "BP" Planned Business Park district: "Common brick, common concrete blocks without architectural finish, corrugated metal or pre-engineered metal components installed with exposed fasteners, and precast 'T' shaped concrete wall sections are prohibited on any building exterior wall." The next paragraph adds that architectural quality must be equal on all sides so that every side of the building is finished. BP is a district for office, sales, distribution, warehouse, light manufacturing and fabrication and related service uses, and a dwelling is not among its permitted uses. That paragraph is the whole of the subject: the word corrugated appears once in the Order's 204 pages and that is the once. The "AG" Agricultural district, the "RE" Rural Estates district and the R-80 through R-7 single-family districts set permitted and special uses, height, front, side and rear yards, lot width, lot area and coverage, and none of them says anything about wall or roof material, roof pitch, eave projection or architectural review. The Order's one general power to impose conditions on "architectural design and aesthetics" is the site development plan under § 400.350, and its first sentence excludes "a detached single-family or two-family residence or ... structures accessory thereto" from needing one at all. Nor is there a floor-area floor for a site-built house: the only minimum floor area in the Order is 500 square feet, and it applies to a mobile home unit in a mobile home park under § 400.420. What the county does require on a new dwelling is a sealed set — its own permit list asks for footing, wall, floor and roof drawings with the size and spacing of every member, sealed by an engineer licensed in Missouri, plus a signed plan certification statement against the 2018 IRC and 2018 IECC as amended.

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 Platte County

All nine services are available in Platte 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 Platte 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 Platte County. Tell us what you want to build and we will draw it to them.

Start your project

Where we build around Platte County

Platte 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 Platte 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 Platte 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.

Clay County

Buchanan County

Kansas City

Jackson County

Building in Platte County: common questions

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

Start your project

Does Platte County actually inspect a house, or is this one of those Missouri counties where nobody looks?

It inspects. Platte County is a first-classification county, and RSMo 64.170 empowers counties of the first and second classification — and only those — to control construction and issue building permits. Platte County has taken that up: it has adopted the 2018 International Building, Residential, Plumbing, Mechanical, Fuel Gas, Energy Conservation and Swimming Pool and Spa Codes and the 2017 National Electrical Code, with amendments in County Commission Order No. 2019-CO-181, and its Planning and Zoning Department reviews the plans and inspects at footing, pre-backfill, ground rough, rough-in — framing, electrical, plumbing and mechanical — and final. Nothing may be occupied until the building official issues a certificate of occupancy. That is a real building department doing real inspections, and it is not the norm across the state: there is no statewide residential code in Missouri, and 89 of the 114 counties are third classification, which RSMo 64.170 does not empower to have a county building code at all.

My address says Kansas City but my mail comes to Platte County. Who permits my build?

Whoever's boundary the parcel is actually inside — and in Platte County that question is unusually live, because 55,477 of the county's 113,207 residents live within the Kansas City city limits. If the parcel is inside the city line, Kansas City permits it under its own Chapter 18 building code, administered by the city's director of city planning and development, and the county's building department has no part in it. If it is inside Parkville, Platte City, Riverside, Weatherby Lake, Weston or any of the other municipalities, that city decides. Only if the parcel is in the unincorporated balance of the county — 30,603 people in 2024 — does the county's own code and Zoning Order apply. RSMo 64.180 is the reason: a county building code adopted under RSMo 64.170 to 64.200 'shall be applicable to the unincorporated territory of the county'. A mailing address will not tell you which side of that line you are on; the recorded legal description and the county's own zoning map will.

Everyone tells me a barn does not need a permit. Is that true here?

No. Platte County's own published fee schedule has a line headed BARN / GARAGE / SHED PERMIT — $50.00 for the first 500 square feet or portion thereof plus $0.10 per additional square foot for a barn or garage — which is the county telling you in its own document that a barn is permitted work. The agricultural carve-outs that do exist in Platte County are narrower than the rumour. The Zoning Order exempts 'Agricultural uses' from the Land Disturbance Permit, and its Sediment and Erosion Control Regulations apply by their own terms to land disturbance 'for non-agricultural uses'. Neither of those is an exemption from the building code, and there is nothing in RSMo 64.170 to 64.207 — the sections that create county building-code authority — exempting farm buildings from it. In the AG district the Zoning Order handles farming as a permitted use, not as an exemption: 'All agricultural uses' are permitted as of right, and 'A primary single-family detached residence' is listed separately, on its own line. A house is a house whatever the cladding is.

What is loess, and why does everybody here talk about it?

Loess is silt that the wind picked up off the Missouri River flood plain after the last glaciation and dropped on the uplands, and Platte County is in the heart of it — the USDA calls this land resource area the Iowa and Missouri Deep Loess Hills. It builds the steep, smoothly rounded, sharp-crested hills above the river, and it will stand almost vertically in a fresh road cut, which is why people notice it. For a build it means two things. First, the material itself: the NRCS series description for Knox, the soil on the dissected hills and bluffs along the river here, records less than 5 percent sand anywhere in the profile and slopes running from 2 to 35 percent — a fine silt on a hillside, which drains and compacts nothing like the sandy or gravelly fill a crew from elsewhere may expect. Second, the subsoil: Sharpsburg, the soil on the wide loess ridgetops that make up the largest single association in the county, is classified fine and smectitic and carries 36 to 42 percent clay, and smectite is the clay that swells wet and shrinks dry. The practical answer on any specific parcel is a soil investigation, because the two problems sit on different parts of the same farm and the county's own inspection sequence starts at the footing.

I have more than three acres. Do I still need a septic permit?

Probably yes, and the reason is Platte County specifically. RSMo 701.031 excludes the owner of a single-family residence lot of three acres or more from the state on-site sewage provisions, and that is the exemption most people have heard about. But RSMo 701.047 leaves a county free to adopt more restrictive standards of its own, and Missouri's Department of Health and Senior Services records Platte County's authority type as 'Ordinance', naming the Platte County Health Department as the permitting agency and warning that 'This county has their own Onsite Wastewater Ordinance and may have additional requirements beyond the state minimum construction standards.' The county closes the same loop from the building side: its checklist for a one- or two-family dwelling permit requires a septic permit from the Health Department, or a sewer permit from the Platte County Regional Sewer District or Timber Creek Sewer Company, plus a letter from the applicable water district confirming water is available, before the building permit issues. Ask the Health Department about your parcel before you ask anyone about a house plan.

How big does my lot have to be, and where can the shop go?

It depends on the district, and the shop is governed differently from the house. In AG Agricultural, each dwelling and its accessory buildings need 40 acres of lot area with 400 feet of lot width at the front building line; RE Rural Estates needs 5 acres; R-80 Rural Single-Family needs 80,000 square feet, about 1.84 acres. Height is 35 feet in all three and buildings may not cover more than 25 percent of the lot. The setbacks are where a detached shop gets placed: in AG the Zoning Order sets a 100-foot front yard and a 30-foot side yard for the dwelling on an interior lot, but requires 'accessory buildings other than dwellings' to sit not less than 100 feet from every exterior and interior side lot line, with a 100-foot rear yard for the dwelling and 50 feet for an unattached accessory building. In RE and R-80 an unattached building accessory to a dwelling takes 15 feet on the side instead. There is one relief valve for landowning families: § 400.551 allows a Family Unit Subdivision in AG, RE, R-80 and R-40 that may modify — but not eliminate — yard, setback, road frontage, lot width and lot area, provided the aggregate density is unchanged and the residents are immediate family, meaning parents, children, siblings or grandchildren, attested by affidavit.

What will the county charge me, and how long does it take?

Platte County prices residential permits on floor area, not on construction value. A one- or two-family dwelling is $200.00 for the first 500 square feet or part thereof plus $0.25 for each additional square foot up to 1,400 square feet; from 1,401 square feet up it is $300.00 for the first 500 plus $0.35 for each additional square foot. A detached barn or garage is a separate $50.00 plus $0.10 per square foot after the first 500; a deck is $50.00, a pool $75.00, an electrical or solar permit $50.00. On timing, the county states that an application 'shall be reviewed and acted upon within five (5) working days after the receipt of all the required information' — the qualifier is doing the work in that sentence, because the required information for a dwelling is a long list: sealed drawings by an engineer licensed in the State of Missouri, a sealed truss design where trusses are used, a site plan by a surveyor licensed in the State of Missouri, an erosion and sediment control plan, a REScheck or HERS rating under the 2018 IECC, the septic or sewer approval, the water district letter, the road entrance permit and a signed plan certification statement. Starting work before the permit issues doubles the fee and can draw a stop work order.

Is there anything about the airport I need to know?

Only if you are building tall, and mostly you are not. Kansas City International Airport lies within the Kansas City portion of Platte County, and rather than writing its own approach surfaces the county's Zoning Order § 400.400 provides that heights in the areas around KCI 'shall be governed by the regulations established by the City of Kansas City, Missouri, and adopted hereby by reference'. Around airports without an established approach plan the Order applies its own scale within 10,000 lineal feet of the boundary — 15 feet at the edge, then 10 additional feet per 200 feet of distance for a runway under 3,950 feet, 5 feet per 200 feet for a longer one, and 4 feet per 200 feet where the runway is an instrument runway. Since the AG, RE and R-80 districts cap every building at 35 feet regardless, the airport rules generally reach a tall accessory structure rather than a house. Interstate 29 and the airport are the reason this county has both metro access and open ground, which is the whole appeal of building here.

Building in Platte 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