Eastern Idaho Shop Building Questions

On this page

• Cost
• Snow & engineering
• Permits & the ag exemption
• Process

Snow & engineering

The design load is decided once, at the drawing stage, and it is not cheap to revisit.

What snow load do I have to design for?

Whatever your permitting jurisdiction has adopted, which is not always the newest research figure. The City of Idaho Falls requires a 47 psf ground snow load, a number that traces to the 1986 edition, while the 2015 University of Idaho study calculated 23 psf for the same location. The adopted figure governs. Unincorporated Bingham County publishes a formula instead, in Bingham County Code Title 8, §8-1-2-1: ground snow load = (elevation ÷ 100) − 5. Blackfoot at 4,498 feet: 4,498 ÷ 100 = 44.98, minus 5 = 40 psf, where the 2015 study calculated 28 psf — the adopted number is the higher one there too. Confirm the number with the office that will stamp your plans before ordering trusses.

Why does the next town over have a different number?

Elevation is one input to the model, not the whole of it. In the 2015 study Iona sits at 4,783 feet with 23 psf while Roberts sits at 4,777 feet with 33 psf — six feet apart vertically, ten pounds per square foot apart on paper. Ririe carries 59 psf and Ammon 24. Terrain, exposure and the station data behind each point all move the result, so a truss package priced off a neighbouring town's figure is priced off the wrong figure.

How deep do the posts have to go?

The City of Idaho Falls publishes a 30-inch frost line, and Bingham County lists a 30-inch frost depth. Jefferson County Ordinance 2017-01 amends IRC Table 301.2(1) to a 30-inch frost depth with a −4°F winter design temperature; that came from a scanned document, so confirm it with the county at (208) 745-9220. Bearing conditions can require going deeper than frost depth, which is a soils question rather than a code minimum.

What happens if the excavation hits rock?

It happens across the Snake River Plain, where loess sits over basalt at shallow depth. No source publishes a dollar figure for a basalt excavation premium here, so anyone quoting you one is quoting their own rate, not a market rate. Rock work sits inside the published $3,000 to $20,000 or more site-prep range. Get the rock contingency written into the bid before excavation starts rather than settled after.

Process

Where a timeline figure is not published, this page says so rather than estimating it.

How long does a build take?

No jurisdiction on this list publishes a permit processing time, and putting an invented figure here would be worse than useless when you are planning around it. What is knowable is the sequence: design and engineered stamped plans, which run $1,500 to $5,000, then permitting, then site prep, then the shell, then slab and finish work. Ask the permitting office for its current turnaround when you file, and ask any builder bidding the work for their current lead time in writing.

When should I start for a building closed in before winter?

Work backward from the ground rather than from the calendar. Footings go to a 30-inch frost depth here, and excavation and concrete both want unfrozen ground, so the site-prep and slab stages are the constrained ones. Everything ahead of them — design, engineered plans, and permitting through an office that publishes no processing time — has to be finished before that window opens. Starting the design and permit conversation well ahead of the season you want to build in is the part you control.