Building types · Eastern Snake River Plain
This is where the Snake River Plain shows up in the invoice. Depth to basalt changes across a few miles, and it decides what a post hole and a slab actually cost.
Mon–Fri 8am–5pm · Idaho Falls and the surrounding towns
Send the address and the size you have in mind. You’ll get the design load your jurisdiction requires and the office that permits it.
Idaho Falls sits on wind-laid loess over basalt. How much loess you got is a matter of where the wind put it, and it varies by soil series over short distances.
The USDA series descriptions carry the numbers. Polatis silt loam, mapped widely across the loess-covered lava plains of southeastern Idaho, lists depth to bedrock at 20 to 40 inches. The required frost depth here is 30 inches to the bottom of the footing. On the shallow end of that range, basalt sits above the depth code requires your footing to reach.
Above the rock there is often caliche — a cemented carbonate horizon that drills like soft rock. Pancheri silt loam carries a calcic horizon 6 to 15 inches down, and Ririe silt loam on the benches starts its calcic horizon at 7 to 16 inches. Neither stops a building. Both change the excavation.
USDA official soil series descriptions. Your parcel's actual profile can differ from the mapped series; a test hole is what settles it.
The cost ranges further down this page are real published figures. The one number that matters most on shallow ground is not among them, and it is worth saying plainly: no source publishes a dollar figure for basalt excavation premium in this market.
So this page does not quote one. Rock premium depends on how deep the rock is, how hard it is, how much of it has to come out, whether the machine on site can break it, and whether access allows a bigger one. Those are parcel-specific facts.
A site visit is what settles it. Any flat per-hole rock price offered before someone has looked at the ground is a number picked, not a number measured.
Published market ranges, not a quote. Where a range is wide, the spread is usually access, haul distance and how much material has to move.
Site prep is the widest range in the whole build, and that width is honest. A flat, cleared, well-drained pad with truck access off a county road sits at the bottom. A sloped parcel needing clearing, cut and fill, imported base and a new approach sits at the top or past it.
Everything here happens before there is a building to look at, which is why it is the easiest scope to leave vague in a bid and the easiest place for two quotes to stop being comparable. Ask which of these four lines each bid includes.
Four inches with wire mesh handles vehicles, benches and light storage. Lifts, forklifts, loaded RVs and stacked equipment call for a thicker slab and a heavier reinforcement schedule. Decide by the heaviest thing that will sit on it, not by the average.
A compacted granular base gives the slab uniform support and lets water drain away rather than sit under the concrete. Depth depends on the native soil — silt loam that holds moisture wants more base than a well-drained gravelly profile. Compaction in lifts matters more than raw depth.
Non-negotiable in a shop you intend to heat. Without it, ground moisture drives up through the slab and condenses inside the building — damp floors, rusted tools, coating failures. It costs very little at pour time and cannot be retrofitted.
Idaho Falls averages 186 days with a low at or below freezing and 58.8 days that never rise above it. The NRCS puts the frost-free season on these soils at 55 to 120 days.
Concrete placed into hard frost is a problem, and excavation into frozen ground is slow and expensive. So the schedule runs backwards from the pour: a building you want closed in before winter is a conversation that starts in spring, not in September.
Post-frame shops from 24x32 up, sized around door height, truss spacing and the snow load your jurisdiction adopts.
Clear height drives the price: a 14 ft door needs roughly 16 ft of sidewall, and that changes post and truss spec.
Send the parcel address and the footprint you have in mind. You'll get the mapped soil series under it, the frost depth and design load that apply, and a straight answer on what still needs a site visit.