Barndominium building in and around De Soto, KS

Inside De Soto city limits, the City of De Soto's Building Inspection Department issues the building permit. Outside city limits, Johnson County Building Codes does. Johnson County asks you to confirm the address is unincorporated with its address search before applying.

Contractor rules differ slightly. De Soto's application says all trades must be licensed with Johnson County Contractor Licensing. On the county side, Johnson County lets a homeowner pull the permits and do the work only on a home they will occupy themselves, not one built for sale or lease (Johnson County building permits). Contractors you hire still need a county license.

A few miles west, toward Eudora, you cross into Douglas County, with different offices and rules. Our Lawrence page covers that side.

De Soto's own new-dwelling application plans for homes on private wastewater. It asks you to choose city sewer or private wastewater, and says a private system's design and application are due at the house-permit stage. Whether a given in-city parcel has room for a house, a shop and a septic field depends on its size, soils, zoning and any recorded covenants. We check those before design.

What De Soto asks for on a new dwelling:

• A plot plan stamped by a licensed surveyor
• Building plans stamped by an architect or engineer, plus supporting documents such as truss and I-joist plans
• An energy auditor, because a blower-door test is required on all new dwellings
• Contractors for every trade, licensed with Johnson County
• A right-of-way work permit, which the same application covers

That list is useful for checking a shell quote. A delivered shell doesn't include sealed plans, a surveyed plot plan, a tight conditioned envelope or the final test. Ask who carries each one. Apply through the city's online portal, linked from its permit application forms page. That page says the PDF applications, including the new dwelling application, will no longer be available soon.

The path depends on which side of the city line you're on.

Sources: De Soto private sewage disposal permit and JCDHE residential systems.

For a barndominium, the trap is treating "unused acreage" as the septic field. The field, its replacement area, the house, the shop, the driveway and any future addition all compete for the same good soil. Run the soil test before you fix the footprint, then place the buildings around the system.

On county land, the 2025 Sanitary Code requires at least two acres for a single-family septic permit. The owner of a lot recorded or platted before April 7, 2006 can apply for a variance from that minimum. JCDHE grants it only if, in coordination with county Planning, the system can meet every other code and zoning requirement.

For unincorporated parcels, Johnson County's rules add a few more questions:

• Is it big enough for a house at all? In the county's Rural (RUR) district, each new dwelling needs a nominal lot area of at least 10 acres, unless the tract was a lot of record on April 7, 2006 (Article 9). The county also warns that a substandard parcel "may severely restrict" your ability to get building permits.
• Which zoning rules are in effect? Johnson County is rewriting its zoning regulations (Zoning Regulations Update). Confirm the version in effect when you file.
• Who provides water? Water providers differ by parcel and each sets its own connection charges. Get the provider, connection cost and any line extension in writing for the exact address.
• Where does the driveway go? A new entrance on a county road needs a $75 Public Works entrance permit, with an inspection after the culvert goes in and a final before occupancy.
• Do you have an address? Johnson County won't issue a building permit without one, so request it early.

Our cost guide uses national benchmarks: HomeGuide (January 2026) lists kit materials at $20–$35 per square foot, kit plus assembly at $30–$50, and completed construction at $65–$160, excluding land. The kit and assembly figures exclude site prep, foundation, utilities and interiors.

Worked example: the cost guide's 40×60 has 1,600 square feet of living space and an 800-square-foot shop. Around De Soto, here is what gets added to the building contract, depending on the wastewater path:

The kit-versus-finished gap matters most here. A $30–$50 per square foot kit-plus-assembly number does not include the slab, the septic system or anything inside the walls. Compare proposals at the same finished scope. See our shell and kit page for what each scope includes.

1. Confirm the jurisdiction: City of De Soto or unincorporated Johnson County.
2. Decide the wastewater path. Check for city sewer; if there isn't any, order the soil evaluation. On a county lot under two acres, ask about the pre-2006 variance first.
3. Lay out the house, shop, septic area and driveway together, with bedrooms and future additions decided.
4. Get the surveyed plot plan and sealed building plans.
5. Apply. In the city, use the portal, with the private-system design if needed. In the county, get the JCDHE installation permit, then apply in MGO Connect.
6. Book the energy auditor for the blower-door test (city) and meet the energy compliance submittal (county).
7. Close out: final wastewater inspection and as-builts, entrance final, then the final building inspection.

Can I have a septic system inside De Soto city limits?

Yes, where city sewer isn't the path. De Soto's new-dwelling application offers a private wastewater option, and the city issues the private sewage disposal permit after a soil profile test.

Does De Soto require a blower-door test?

Yes. The city's new-dwelling application says a blower-door test is required on all new dwellings and asks you to name an energy auditor.

How much land do I need for a septic system near De Soto?

On unincorporated Johnson County land, the Sanitary Code requires at least two acres for a single-family septic permit, with a variance path for lots of record before April 7, 2006. Zoning separately requires 10 acres per new dwelling in the Rural district unless the tract was a lot of record on that date.

Do I need sealed plans for a barndominium in De Soto?

Yes. The city requires building plans stamped by an architect or engineer and a plot plan stamped by a licensed surveyor.

Is a kit cheaper than building with you?

A kit is a materials package. HomeGuide's kit range excludes site prep, foundation, utilities and interiors. Compare it with a finished proposal only after those are added.