Building Permits in Twin Falls: A Homeowner's Guide

TL;DR

1. The first question is not "do I need a permit." It's "who issues it." The City of Twin Falls and Twin Falls County run two separate building departments, in two different buildings, with different forms and different inspectors.
2. Inside Twin Falls city limits, the City handles everything: building, electrical, plumbing, and mechanical.
3. Outside city limits, the County handles the building permit, but your electrical, plumbing, and HVAC permits come from the State (DOPL), not the County. This is the single most common thing homeowners get wrong.
4. Small cities like Kimberly, Filer, and Buhl have their own city processes. Being in the county mailing area is not the same as being in county jurisdiction.
5. Permits are triggered by far more than new construction. Moving a nonbearing wall counts. A new roof counts. A deck over 30 inches counts. Paint and carpet don't.
6. You can draw your own plans for most residential projects. An engineer is only required above two stories or for unusual designs.
7. County residential plan review is usually not more than seven business days with a complete submittal. Incomplete submittals are what cause delays.
8. County building permits expire after 180 days from issuance or from your last inspection. State trade permits expire after 365 days.
9. Mark your property pins before the setback inspection. An unmarked boundary fails the inspection and can trigger a survey.
10. Skipping a permit costs more than pulling one, and it surfaces later at resale, refinance, or an insurance claim.

Nobody enjoys this part. Permits are the least interesting thing about building something, and they're the part most likely to make a homeowner feel like they're being handed a runaround.

So here's the whole picture in one place: who to call, what needs a permit, what you submit, how fees get calculated, what inspections happen and in what order, and what actually goes wrong. I pull permits in this area constantly. This is the version I'd give a friend.

One note before we start. Codes and fees change, and some of the published material out there is out of date, including some of the government's own handouts. I'll point out where that's true. Confirm anything that matters with the department directly before you rely on it.

Which office has jurisdiction over my address?

This is the question that determines everything else, and it catches people constantly. A Twin Falls mailing address does not mean you're inside Twin Falls city limits.

There are two entirely separate building programs here. The City of Twin Falls Building Safety Department sits at 203 Main Avenue East, on the second floor of City Hall. Twin Falls County Community Development Services sits at 630 Addison Avenue West, Suite 1100. Opposite sides of town, different applications, different staff.

That second row is the one to internalize. The City of Twin Falls has assumed local jurisdiction for building, electrical, plumbing, and mechanical permitting and inspection inside city limits. The County has not. Out in the county, the building department handles your structure, and your trades go to the State.

The County's own guidance tells applicants exactly that: additional permits are required for any electrical, plumbing, and HVAC installations, with a referral to the State. Jerome does the same thing, sending residents to DOPL to buy electrical, HVAC, or plumbing permits.

The State's position is that this varies all over Idaho. DOPL's guidance is blunt about it: because the legislature authorized several cities and counties to assume jurisdiction within their boundaries, permit requirements vary widely throughout the state, and even when you hold a building permit from a local jurisdiction, you may still need permits from DOPL for electrical work.

So two neighbors, one inside the city line and one outside it, doing the identical bathroom remodel, follow different processes. That isn't anybody being difficult. It's just how jurisdiction works in Idaho.

If you're not certain which side of the line you're on, call the County at (208) 734-9490 with your parcel number before you do anything else. Your parcel number is on your tax assessment.

What actually requires a permit?

More than people expect, and the trigger language is broad.

In the County, a permit is required any time a building or structure is erected, constructed, remodeled, enlarged, altered, repaired, moved, removed, converted, or demolished. That explicitly includes work inside a building that most people would call non-structural, like moving or erecting nonbearing walls.

In the City, the list is similar and includes some things people don't expect.

Two extra triggers worth knowing. If your property is in the City's historical preservation district, you have to appear before the commission before a permit can be issued. And in the County, if you're remodeling what is currently an unfinished basement or garage, or the total floor area within the roof line exceeds 4,500 square feet, you'll need comment or plan review from your local fire district.

Those fire districts, by the way, are separate agencies with their own phone numbers: Twin Falls, Buhl, Filer, Rock Creek (which covers Kimberly, Hansen, and Murtaugh), and Salmon Tract. Your builder should know which one covers your parcel.

When in doubt, call and ask. The City's building department specifically asks people to call (208) 735-7238 before starting if they're uncertain. That call is free. The penalty for guessing wrong is not.

Do I need an architect?

Usually not, and this surprises people.

For residential projects in the County, you may prepare your own plans. An architect or engineer is only required when the proposed building is more than two stories high, or is of unusual design that would need professional help to ensure structural stability. Foundation walls over nine feet in height also require engineering design.

What you submit is two sets of plans drawn to scale, a quarter inch to one foot, or computer-generated at not less than an eighth inch to one foot. Pages numbered, sets stapled.

The site plan is where most first-time submittals fall short. It needs to show property lines and lot dimensions, official survey corner stake locations, easements and rights-of-way, well and septic locations, all existing buildings and their distances to property lines, the proposed construction with dimensions, the front setback measured from the property line rather than the edge of the road, surface water drainage away from the structure, finished floor elevation relative to the road crown, and the driveway location, length, width, and surface type. Two copies of the site plan need to be stamped approved by South Central Public Health District.

Two County rules that quietly kill designs: no building or structure may be placed within six feet of another structure, and nothing may be placed within an easement area. Check your plat map for easements before you fall in love with a location on the lot.

The building plans need footing and foundation details with reinforcement, floor plans with room uses and window and door headers, egress window and smoke and carbon monoxide detector locations, egress window well details for basements, attic and crawl space access, crawl space venting, floor framing, beams and point loads, vent systems, stair details, at least two elevations, wall shear bracing, and a completed energy compliance certification via RESCheck.

That list looks intimidating written out. In practice it's a normal residential plan set, and it's the reason hiring someone who does this weekly saves you a correction cycle.

How long does approval take?

County residential plan review is usually not more than seven business days, and that timeline is explicitly conditional on submitting complete plans and specifications with all required supporting documents. Applications are reviewed in the order received.

Read that condition carefully, because it's where schedules actually slip. The seven days doesn't start over from a partial submittal, but corrections send you back into the queue. One incomplete site plan can turn a one-week review into three.

The City's initial plan review runs on a similar order of magnitude, roughly a week for straightforward residential work, though complex projects take longer.

How are permit fees calculated?

Not by project cost. By valuation, which is a different thing.

The County calculates fees from a square foot valuation established for the type of construction and the proposed use. The square footage of each use type is multiplied by that established valuation to produce a total building valuation, and the fee schedule is applied to that number.

The City moved to a national reference for this. Effective January 1, 2025, the City of Twin Falls Building Safety Department uses the International Code Council's Building Valuation Data table, published each August, to set the average construction cost per square foot that drives the fee calculation.

The practical consequences:

1. Your fee is not a percentage of what you're paying your builder. It's derived from a published table.
2. Plan review fees are typically due at submittal, before review starts, and are separate from the permit fee itself.
3. Inspection deposits are collected up front in the County, calculated as a percentage of the fee with a stated minimum.
4. Trade permits are separate line items. Electrical, plumbing, and HVAC each carry their own fee, and out in the county those go to the State on the State's schedule.
5. Re-inspection fees exist. If the work isn't ready when the inspector arrives, or correction items aren't done on the return visit, you can be charged to bring them back.

I'm deliberately not publishing dollar figures here. Both jurisdictions revise their schedules, the City's table updates annually every August, and I'd rather you get a real number than a stale one from a blog post. Call the department with your square footage and use type, or ask your builder to.

What inspections will happen, and how do they work?

You get an Inspection Record Card with your approved permit. In most cases every inspection listed will be required, each one has to be requested by the permit holder, and each has to be signed off before you proceed to the next phase. The Inspection Record Card and the approved job site plans must be on site for every inspection.

For County projects, inspection requests can be left 24 hours a day, seven days a week at (208) 734-9490, extension 1. You'll need the permit number, the type of inspection, the project address, and contact information. Requests received by 9:00 AM are generally completed the same day, and requests after 9:00 AM get scheduled for the next workday. Inspectors generally start on the east side of the county and work west, which is worth knowing if you're in Buhl or Filer and wondering why the truck shows up late in the day.

Scheduling a specific time isn't possible without at least 24 hours of prior approval from the building official.

The one that fails most often is the setback inspection. Property pins must be located and property lines clearly marked for the inspector. If there's any question about where the boundary is, the inspection will not be approved, and a survey may be required. Mark your pins before you call. Also post the job address at the road so the inspector can find the site.

What about occupancy?

You cannot use or occupy a new or remodeled structure until there's been a final inspection and an Occupancy Permit has been issued. The Certificate of Occupancy will not be issued if any required inspection was never completed.

Occupancy approval, and sometimes a building permit, is also required before using space in a way that constitutes a change of use. Converting a garage to living space is the classic example. So is enclosing a covered patio, or using residential space for a home business, or turning an office into a shop.

Build in time between "the project looks done" and "we move in." Final inspections and occupancy approval take some scheduling.

One local quirk worth knowing about basements. In the County, where a basement is declared unfinished and therefore non-habitable, the homeowner is required to record a statement attached to the deed declaring the basement unfinished before final occupancy is issued. At least one window in an unfinished basement must meet egress requirements, and any proposed future bedrooms down there will have to meet egress too.

That recorded statement follows the property. It's a common surprise during resale, and it's a good reason to think hard about whether you want that basement finished as part of the original permit rather than later.

What happens if I skip the permit?

It's a bad trade, in four separate ways.

Financially. In the County, the minimum penalty for work started without a permit is an amount equal to the building permit fee, meaning you pay the fee twice at best. The City's building official may assess an escalating penalty for failure to obtain a permit, assessed in addition to the permit fee, and payable before work continues or inspections happen.

At resale. Unpermitted work shows up in inspections and appraisals. Buyers ask for the permit history, and "we just did it ourselves" reduces to a price concession or a dead deal.

On insurance. A claim involving unpermitted work is a claim your carrier will look at closely.

Structurally. The inspections exist because things get missed. Egress, headers, footing depth, and shear bracing are not paperwork items.

There's also a contractor angle. An unregistered contractor cannot obtain a building permit in Idaho at all. If someone bidding your job suggests you pull the permit yourself as the homeowner, ask why. Sometimes there's an innocent answer. Sometimes it means they can't. Our registration number is RCE-65510, and I'd rather you verify it than take my word for it. I wrote a separate piece on how to check any Idaho contractor in about ten minutes.

Twin Falls County design criteria

Worth bookmarking. These are the numbers your plans have to be designed to, from the County's current published criteria.

Twin Falls County has adopted the 2018 versions, with Idaho Amendments, of the International Building Code, International Residential Code, Energy Conservation Code, Mechanical Code, Fuel Gas Code, International Existing Building Code, and the 2018 Fire Code, plus the 2018 Idaho Manufactured Home Installation Standards.

A caution here. The County's downloadable residential handout is dated 2014 and still says the county adopted the 2012 International Building Code with a 90 mph wind load. The County's current permit information page says 2018 codes and 115 mph. Those are not the same design. If you found a PDF and designed to it, verify the criteria with the department before you build. This is exactly the kind of thing that produces an expensive correction.

A note on the word "licensed"

You'll see it on government pages too. The City's forms page advises hiring a contractor who is licensed through the state of Idaho. Kimberly's FAQ says general contractors must be registered or licensed with the state, and points to the old Division of Building Safety Electrical Bureau, an agency that has since been folded into DOPL.

Idaho does not license general contractors. It registers them. That distinction matters when you're evaluating a builder, and I've written up the full explanation, including how to verify anyone yourself in about ten minutes.

Working with a builder who handles this for you

We pull permits in Twin Falls, Kimberly, Jerome, Buhl, Filer, Burley, Rupert, and unincorporated Twin Falls County. We know which office covers which address, which fire district reviews which parcel, and what a complete submittal looks like so your review doesn't get sent back.

We're a registered Idaho contractor, RCE-65510, insured and warrantied, building custom homes, remodels, additions, barndominiums, and ADUs across the Magic Valley. You'll get one point of contact, a real itemized estimate, and a straight answer about timeline including the permitting piece.

Tell us about your project → or call (208) 731-1729

Frequently asked questions

How do I know whether I'm in the city or the county? Call Twin Falls County at (208) 734-9490 with your parcel number, which appears on your tax assessment. A Twin Falls mailing address does not establish city limits, and plenty of homes with Twin Falls addresses are under county jurisdiction.

Do I need a separate permit for electrical and plumbing? Yes, and where you get it depends on your address. Inside Twin Falls city limits, the City handles building, electrical, plumbing, and mechanical itself. Outside city limits, the County handles your building permit and your trade permits come from the State through DOPL. Even when you hold a local building permit, DOPL permits may still be required.

How long is my permit good for? County building permits expire 180 days after issuance or after your last inspection, whichever is later, and keeping it alive is the permit holder's responsibility. State trade permits for electrical, plumbing, and HVAC expire 365 days after purchase or last inspection, and can be renewed for another year for a fee.

Do I need a permit for a shed? Generally not if it's a detached accessory building under 200 square feet accessory to your residence. Over 200 square feet, yes. Note that a permit is also required for carports, garages, covered decks and patios, and any deck with a floor more than 30 inches above the ground.

Do I need a permit to finish my basement? Yes. It's a remodel and it involves egress, electrical, and usually plumbing and mechanical. If the space is currently unfinished basement or garage, the County also requires comment or plan review from your local fire district. And if a basement was previously declared unfinished, there may be a statement recorded against your deed that needs to be addressed.

Can I draw my own plans? For most residential projects, yes. An architect or engineer is only required when the building is more than two stories or of unusual design requiring professional assistance for structural stability, and for foundation walls over nine feet. You'll submit two scaled sets plus site plans.

How much will my permit cost? Fees are based on a valuation calculated from square footage and use type rather than on what you're paying your contractor. The City has used the ICC Building Valuation Data table since January 2025, updated each August. Plan review fees are typically due at submittal, inspection deposits are collected up front, and trade permits are billed separately. Call the department with your square footage for a current figure.

What happens if I already did work without a permit? Stop and call the department. The County's minimum penalty is an amount equal to the permit fee, and the City can assess an escalating penalty on top of the permit fee, payable before any inspections proceed. Coming forward voluntarily is a much better position than being found during a resale inspection.

Why did my inspection fail before the inspector even looked at the work? Most often, unmarked property lines at the setback inspection. Property pins must be located and lines clearly marked, and if the boundary is in question the inspection won't be approved and a survey may be required. Also make sure the Inspection Record Card and approved plans are on site and the address is posted at the road.

Can I schedule an inspection for a specific time? Not usually. County inspection requests can be left any time at (208) 734-9490 extension 1, and requests in by 9:00 AM are generally handled the same day. A specific time slot requires at least 24 hours of prior approval from the building official, and inspectors generally work east to west across the county.

Does my contractor handle all of this? A good one does, and should be able to tell you which jurisdiction your address falls under before you sign anything. Note that an unregistered contractor cannot legally obtain a building permit in Idaho, so if someone asks you to pull the permit as the homeowner, find out why before you agree.

Sources: Twin Falls County Community Development Services and Building Department; City of Twin Falls Building Safety Department; Idaho Division of Occupational and Professional Licenses. Verified August 2026. Codes, fees, and procedures change, and some published handouts are out of date, so confirm current requirements with the department that covers your address.

Related: Registered vs. Licensed in Idaho · Remodels & Renovations · Home Additions