2-Story Barndominium in Missouri

Per square foot it usually is, and the reason is that the two most expensive components do not change. A 3,200-square-foot house on one level needs 3,200 square feet of foundation, slab and roof. The same house on two levels needs 1,600 of each, plus a floor system and a stair. In Missouri the foundation half of that saving is bigger than it looks, because the frost line sets the bottom of every pier before anything else is decided — 36 inches under the Kansas City Residential Code at KCMO Code section 18-57, under Lee's Summit's section 7-902 and under Cass County's amended R403.1.4, 30 in Boone County, St. Charles County, Columbia, the City of St. Louis and St. Louis County, 24 in Springfield, 18 in Branson and 15 in Sikeston. Halving the footprint halves the number of holes at that depth. What eats into the saving is the floor structure, the stair, and the wider footings the second storey draws — Clay County's own Residential Construction Regulations step the minimum footing width from 12 inches to 15 under a two-storey structure. It is usually still the cheaper answer; it is not free.

Whether anybody requires it depends entirely on your jurisdiction, and the prescriptive routes that exist stop before you get there. Cass County Code section 500.040's Post Frame Building Standards cover post-frame buildings for agricultural or residential accessory uses and set the ceiling at 3,000 square feet of area, 14 feet of sidewall height and one story, and 40 feet of maximum width; past any of those a building shall be designed in accordance with the 2006 editions of the International Building Code by a registered Missouri structural engineer. Camdenton states that buildings built to its post-frame standard are not intended for residential or commercial uses and that a post-frame building intended for residential use must have plans prepared by a design professional licensed by the State of Missouri. Lee's Summit goes further and sets no threshold at all: Code section 7-137.A requires that a registered design professional licensed by the State of Missouri shall prepare the construction documents for a permit application, and the city's residential submittal list asks for drawings sealed and signed. In a third-classification county with no building code there may be nobody to require anything, and that is the case where it is most worth doing anyway — a sealed set from a Missouri-licensed professional engineer is what a lender or an insurer is most likely to ask for. Where no requirement exists, RSMo 327.101 permits design services for a dwelling house without an architect's licence only where the drawings, specifications, estimates and reports indicate the person is not licensed as one.

The one in your jurisdiction's zoning ordinance, and it is usually the first thing a second storey tests. Boone County sets 35 feet for a non-farm building in every agricultural and residential district, with an escape route: it can be extended to 100 feet by setting back one extra foot for each foot of height, or by conditional use permit. Lee's Summit's Table 6-4 caps structure height at 40 feet in AG, RDR and RLL. Camden County allows 50 feet above finished grade in A-1, A-R and R-1. The tighter numbers are on the accessory side and they are written as ratios rather than as absolutes: Boone County's accessory-structure definition stops at three storeys or 24 feet and adds that it shall not exceed the height of the main structure, so a tall shop bay beside a single-storey house is a question to settle with the building official before anything is ordered. Branson provides that no accessory structure shall exceed the height of the site's principal structure. Cass County's zoning order limits an accessory building other than a farm structure to one story with a maximum sidewall height of fourteen feet, sixteen upon approval of submitted sealed engineered drawings, while farm structures themselves carry no height restriction under that order. Which of those you are reading depends on whether the building is a dwelling, an accessory structure or a farm structure — three categories with three different answers.

Structurally yes, and it is the most demanding configuration on the page, because the floor spans what the shop spans and lands on the same columns rather than on a shortened interior bearing line. Regulatorily, the thing to watch is that a full floor is a storey and not a loft, and several Missouri instruments are written in storeys. Cass County's Post Frame Building Standards stop at one story, and beyond that limit the building must be designed to the 2006 International Building Code by a registered Missouri structural engineer. The same county's zoning order limits an accessory building other than a farm structure to one story with a fourteen-foot maximum sidewall, sixteen with sealed engineered drawings. Boone County's accessory-structure definition allows up to three storeys but caps the same building at 24 feet and at the height of the main structure, whichever binds first. The occupancy question is separate and stricter: Boone County provides at Section 7.1.5.4 that accessory buildings may not be used for dwelling purposes except as a permitted accessory dwelling, and Cass County's accessory-building packet states that an accessory structure shall not be used as a dwelling and warns that any other use would be a violation of the Cass County Zoning Ordinance. Living space over the shop is a design and a permitting decision that has to be made before the frame is ordered.

Whichever residential code your jurisdiction has adopted, and Missouri jurisdictions are on strikingly different editions, so the honest answer is to name the edition before quoting a requirement. Among the jurisdictions researched for this site, Cass County is on the 2006 International Residential Code with the 2005 National Electrical Code, Jefferson County and Boone County are on the 2015 editions, Springfield, Kansas City and Lee's Summit are on 2018, St. Charles County and Columbia are on 2021, and the Mid-County Fire Protection District at the Lake of the Ozarks publishes the 2024 IRC with the 2023 NEC. The stair, guard, handrail and emergency escape provisions all live in that adopted edition and they have changed between editions. In a Missouri county with no building code the provisions are not enforced by anyone, which does not make them a bad specification — it makes them the specification you and your designer choose to build to. Two Missouri wrinkles are worth knowing. Where a jurisdiction has adopted something, it may have amended it: Boone County upgrades the dwelling-to-garage separation at R302.6 from half-inch to five-eighths-inch gypsum board with the garage completely separated from the residence and its attic. And where a fire protection district has adopted a code under RSMo 321.220, the district may be the body enforcing it — Camden County's own planning packet tells applicants that four named fire departments do building code inspections and that their signature is required on the county's sign-off sheet.

It changes the width and the bearing check more than it changes the depth, because the frost line is set by climate rather than by what sits above it. Clay County publishes the clearest Missouri statement of the step: minimum footing width 12 inches, 15 inches under a two-storey structure, 23 inches under a three-storey, with the bottom of all footings thirty-six inches below the adjoining ground surface and concrete at no less than 2,500 psi for footings. The bearing question is where Missouri counties diverge most sharply. Cass County adds to R401.4.1 that the load-bearing values of soils in Cass County shall be assumed to be 2,000 psf for typical clays, so there is a published starting point. Nothing in the Jackson County Code fixes a presumptive bearing value, so allowable pressure under a pier or footing there is a site question established on the ground. And the soils in that metro are the reason it matters: the dominant Jackson County series are classified smectitic and Vertic, which is shrink-swell clay stated in the taxonomy itself. Put more load on a narrow footing over shrink-swell clay and the failure mode is differential movement, not crushing. A test hole in the actual footprint answers it in a day.

Yes, because lateral force is a function of mass and mass goes up with the building. How much it matters depends entirely on where you are standing, and Missouri's spread is the widest of the states in this series. On the USGS seismic design service at the ASCE 7-16 reference document, Risk Category II, the mapped short-period spectral acceleration is 3.154 g at New Madrid and 0.085 g at St. Joseph — roughly a factor of 37. The adopted categories track it: the City of Sikeston prints seismic design category E in the Table R301.2(1) inserted at section 500.090.A.1 by Ordinance No. 6250 of 6 December 2021, while Kansas City, Lee's Summit and Cass County all print A. In a post-frame or steel-frame building the lateral system is the diaphragm plus the frames and braced bays, so the design consequence is about connection detailing and the load path down to the foundation. In southeast Missouri there is a second problem underneath: the alluvial soils carrying that demand are the same ones the state hazard mitigation plan models for liquefaction, which attacks post embedment and slab bearing rather than the frame above. One counter-intuitive point worth knowing — Missouri's own seismic statute will not force any of this on a house. RSMo 319.203 exempts single-family and duplex residences from sections 319.200 to 319.207 outright, and separately exempts any private structure under 10,000 square feet. What reaches your building is the local adopted code, or nothing.

It depends on the slope and on the frost line, and the two answers are not interchangeable. A walkout is cheapest where the ground already falls, because the cut is work you were doing anyway and the frost line has already taken the excavation part of the way down: 36 inches in Kansas City, Lee's Summit and Cass County, 30 in Boone County, St. Charles County, Columbia, the City of St. Louis and St. Louis County, 24 in Springfield, 18 in Branson, 15 in Sikeston. The deeper the published figure, the shorter the step from a code-depth footing to a wall you can stand behind. A second storey is cheapest on flat ground and where the excavation would be fighting something — chert, a fragipan, a claypan with a winter perched water table, or karst. Around the Lake of the Ozarks the Bardley soils run 20 to 40 inches to dolomite against a 24-inch frost line in the lake towns, so the footing depth and the rock contact are often the same elevation, and cutting into the hill is the better drawing. In the northern claypan counties the Mexico series carries a perched water table between half a foot and a foot and a half of the surface from December to May in most years, which is a drainage design rather than a reason not to dig. On a flat prairie parcel in Cass County with 2,000 psf clays and no slope, going up is usually the simpler answer. Both decisions want the parcel's soil map units and a test hole before anyone prices anything.