How much does it cost to build a custom home in Bonneville County, Idaho? With SwagerBuilds, construction starts at $450 per square foot of conditioned space and goes up from there. A 2,000 square foot custom home in Idaho Falls, Ammon, Iona or Ucon is about $900,000 in construction cost and about $1.2 million all-in once land improvements, permits, design, landscaping and contingency are added. The all-in number is usually about 30 percent above construction cost. Production and semi-custom builders in the county price well below that, and if a $450 starting point is outside your budget, one of them is the right call.
I am Bryce Swager, owner of SwagerBuilds. Four generations of my family are from Rigby, 20 minutes north of Idaho Falls, and Bonneville County is a home market for us. Here is what the number includes, what sits outside it, what the county charges for permits, and how to tell a real price from a placeholder.
What does $450 per square foot include?
Construction cost on conditioned square footage: foundation, framing, roof, windows and doors, mechanical, electrical, plumbing, insulation, drywall, cabinets, tile, flooring, trim, paint, fixtures and the labor to put it all in, managed by a licensed general contractor with a project manager on site. Garages and covered porches are not counted in the square footage, which is why our number looks higher than a builder who spreads the price across the garage slab.
It does not include the lot, site development, permits and county fees, structural engineering, the design fee, landscaping, furniture or a contingency. Those are real money and they are the reason a per-square-foot number alone never tells you what you will spend.
What does a Bonneville County custom home cost all-in?
| Line | 2,000 SF example | Notes |
|---|---|---|
| Construction cost | $900,000 | $450/SF conditioned, fixed after design lock |
| Site development | Varies by lot | City lots in Idaho Falls and Ammon: utility taps and hookups. Rural lots: well and septic, $25,000 to $45,000 combined, plus driveway and power run |
| Permits and county fees | At cost | Tiered off project valuation, plan review separate |
| Structural engineering | At cost | Stamped plans, required on every build |
| Design fee | Fixed, starting at $25,000, quoted per project | Credited in full to your first construction invoice |
| Landscaping, contingency, furnishings | Owner’s choice | 2 to 3 percent contingency is in our fixed-price contract |
| All-in | About $1.2 million | About 30 percent above construction cost on most lots |
Does the cost change between Idaho Falls, Ammon, Iona and Ucon?
The construction cost does not. A house framed in Ammon costs what it costs in Idaho Falls. What changes is site work and review. Idaho Falls infill lots come with city water and sewer, city plan review and sometimes tight access that slows excavation and deliveries. Ammon and Iona acreage lots often need a well and septic even when buyers assume utilities are at the road. Ucon and the rural county add longer driveways, longer power runs and more site grading. The Idaho Falls custom home builder and Ammon custom home builder pages go into the lot-level detail for each.
What does Bonneville County charge for a building permit?
Bonneville County publishes its schedule on the county’s building permit and zoning fees page. Fees are tiered off total project valuation, not square footage, and plan review is a separate line on top of the permit. As of January 2026 the county processes electrical and plumbing permits directly instead of routing them to the state, which means fewer handoffs if your builder has it on the checklist. Planning and Zoning is at 357 Constitution Way in Idaho Falls, (208) 524-7920. The county builds to the state-adopted 2018 IRC. Inside city limits, Idaho Falls and Ammon run their own building departments and their own fee schedules.
On a SwagerBuilds build, permits and county fees are billed to you at cost with the receipts in your JobTread portal. Idaho building permits by county has the full path for Bonneville, Jefferson, Madison and Teton counties.
How do I tell a real price from a placeholder?
A real price has a scope behind it: your lot, stamped drawings, finished selections and subcontractor bids by cost code. A placeholder is a per-square-foot number from a landing page or a phone call with no scope at all. Placeholders feel cheaper because they leave things out, and the gap shows up as change orders six months in. Three questions sort them fast: Is the square footage conditioned space only? Is the price fixed or cost-plus? What has to happen before the price is fixed? Why three custom home bids don’t compare shows how to level them.
How does SwagerBuilds get to a fixed number?
Through the design agreement. Over 12 to 16 weeks we produce the plans, coordinate engineering, finish selections room by room and collect real subcontractor bids. The construction price is fixed at the end of that process, and the full design fee is credited to your first construction invoice. Why we charge a design fee before giving a price explains the reasoning.
How long does a Bonneville County build take?
Plan on 10 to 18 months from permit to move-in, after 12 to 16 weeks of design. Foundations go in during the open season and every SwagerBuilds home is dried in before winter, roof, windows and doors, so interior work runs through the cold months inside a closed shell. The valley floor has a longer open season than Teton Valley, so a Bonneville County foundation can go in as late as October. When to start to be dried in before winter has the month-by-month calendar.
Common questions
Is it cheaper to build in Bonneville County than in Teton Valley?
Our construction anchor is the same $450 per square foot on both sides. The difference is site work and engineering: Teton County snow loads of 85 to 100 psf and 48-inch frost depth add structure, and Teton Valley lots more often need wells, septic and longer utility runs. All-in, a Bonneville County build usually lands lower for the same house.
What does a semi-custom or production home cost in Idaho Falls?
Less than $450 per square foot, often a lot less. Production builders price off repeated plans, builder-grade selections and volume purchasing. If that fits what you want, it is a good product and I will tell you so on the first call. SwagerBuilds builds one-off homes on your lot with your plans, and the price reflects that.
Do you give a ballpark before the design agreement?
Only the one in this post: $450 per square foot and up, about 30 percent more all-in. Anything more specific without your lot and your plans would be a guess, and guesses are how budgets blow up.
Want a real number on your Bonneville County lot?
Bring the lot address, your must-haves and an honest budget to a 15-minute planning call. I will tell you on the call whether $450 per square foot fits, and what the design agreement would produce for you.
This applies on every SwagerBuilds job in Teton Valley and Eastern Idaho. For local specifics, see custom home builder in Driggs, the Tetonia custom home builder page (our West Ridge Ranch lots start construction in 2027), or the Rigby custom home builder page.
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