Post-frame shops & pole barns · Idaho Falls, ID
Ground snow load in eastern Idaho swings from 23 to 59 pounds per square foot across towns 15 minutes apart — and it decides what your trusses cost. Here are the numbers, by town.
Mon–Fri 8am–5pm · Serving Idaho Falls, Ammon, Rigby, Shelley, Blackfoot, Iona, Ucon
Start with the town and a rough footprint. That is enough to pin down the load your trusses have to carry.
| Pg (1986) | |||
|---|---|---|---|
| Blackfoot | 4,498 ft | 28 psf | 23 psf |
| Firth | 4,567 ft | 44 psf | 22 psf |
| Basalt | 4,592 ft | 45 psf | 55 psf |
| Shelley | 4,629 ft | 35 psf | 49 psf |
| Ammon | 4,718 ft | 24 psf | 50 psf |
| Idaho Falls | 4,725 ft | 23 psf | 47 psf |
| Roberts | 4,777 ft | 33 psf | 32 psf |
| Iona | 4,783 ft | 23 psf | 49 psf |
| Menan | 4,803 ft | 30 psf | 37 psf |
| Ucon | 4,807 ft | 25 psf | 43 psf |
| Rigby | 4,851 ft | 32 psf | 41 psf |
| Ririe | 4,963 ft | 59 psf | — |
Source: Ground Snow Loads for Idaho, 2015 Edition (Al Hatailah, Godfrey, Nielsen and Sack, University of Idaho), with the 1986 edition shown for comparison.
Two numbers, and only one of them is binding. The City of Idaho Falls requires structures to be designed for a 47 psf ground snow load — that figure traces to the 1986 edition of the state snow load study. The 2015 University of Idaho update calculated 23 psf for the same location. The adopted code number is the one your permit is judged against. If your jurisdiction says 47, you build to 47, regardless of what a newer study calculated.
What the table is actually for is the comparison across towns. Ririe sits 238 feet higher than Idaho Falls and carries 59 psf in the 2015 study. Firth carries 44. A building designed for one town’s load is not automatically adequate in the next town over. Price off the wrong figure and the number you were given cannot produce the building you were shown.
Bingham County publishes a formula rather than a table. Bingham County Code Title 8, §8-1-2-1 gives ground snow load = (elevation ÷ 100) − 5 — Blackfoot at 4,498 feet: 4,498 ÷ 100 = 44.98, minus 5 = 40 psf, against 28 psf in the 2015 study. The adopted number is the higher one, and the adopted number is the one your permit is judged against. Run your own elevation through it before you accept anyone’s truss quote.
Two bids on the same building can arrive $80,000 apart without either builder being dishonest. Almost always, they are pricing different scopes.
A steel or post-frame package for a 40x60 — posts, trusses, metal skin, fasteners — runs roughly $8 to $18 per square foot. That is the number in the ad. A finished 40x60 shop with a slab, doors, insulation and power runs $30 to $60 per square foot. Trusst Buildings in Shelley publishes $30 to $60 per square foot for its own work, which puts a 2,400 square foot building between $72,000 and $144,000.
Steel Structures America publishes medians from completed projects: 40x60 = $119,721 across 140 builds, 30x40 = $69,894 across 178, 40x80 = $174,000 across 28.
So the finished building lands at roughly three to four times the package price. Neither number is dishonest on its own. The problem is comparing one against the other.
Every dollar figure above comes from a named third party and is credited where it sits. Nobody has priced your building yet.
Idaho Falls sits on the eastern Snake River Plain — wind-laid loess over basalt. How much loess you get varies by the parcel, and it decides what a post hole costs.
Those depths are mapped. The USDA series descriptions record them, parcel by parcel. Polatis silt loam, mapped extensively across the loess-covered lava plains of southeastern Idaho, lists depth to bedrock at 20 to 40 inches. The frost depth requirement here is 30 inches to the bottom of the footing. On Polatis ground, basalt can sit ten inches above the depth the code requires your footing to reach.
Above the basalt there is often caliche. Pancheri silt loam, with its type location in Bingham County, carries a calcic horizon 6 to 15 inches down — very hard, very firm carbonate nodules. Ririe silt loam on the benches starts its calcic horizon at 7 to 16 inches.
None of that stops a building going up. It changes the excavation line item, and it is worth knowing before someone quotes you a flat per-hole price.
Post-frame shops from 24x32 up, sized around door height, truss spacing and the snow load your jurisdiction adopts.
Hay, livestock and implement structures, where the permit path differs from a residential accessory building.
Clear height drives the price: a 14 ft door needs roughly 16 ft of sidewall, and that changes post and truss spec.
Shell-only scope with living space finished separately, which is where most bid confusion on this build type starts.
Added bays and covered wings, where drifting snow against the taller wall raises the design load on the lower roof.
Slab, footings to 30 inches, gravel, drainage and access — the line item that moves most on loess over basalt.
Idaho Falls averages 35.3 inches of snowfall a year and 186 days with a low at or below freezing, with 58.8 days that never get above freezing. Mean snowfall is zero in June, July and August, half an inch in May and under an inch in October.
Concrete sets the outer limit. Footings and slab both need unfrozen ground, which means the pour — not the framing — is what the schedule has to be built around. Work back from it and the design and permit stages land months earlier than most people expect. The NRCS puts the frost-free season on these soils at 55 to 120 days.
Two things get you a real answer: where the parcel sits, and how big you want to go. From those, you’ll know the load your jurisdiction enforces and which office enforces it.