ADU laws in Kansas

In plain words

Kansas has a 2026 law that speeds up ADU approvals. It does not make towns allow ADUs. An ADU, or accessory dwelling unit, is a smaller second home on the same lot as a house. It could be a basement apartment, a converted garage, or a backyard cottage. The By-Right Housing Development Act, also called SB 418, took effect July 1, 2026. By right means staff must approve a project that follows the written rules, with no public hearing or board vote. Under the law, a complete ADU application that meets local zoning must be approved or denied within 30 days. If the town misses that deadline, the application counts as approved. Zoning is the local rulebook for what can be built where. Here is the catch. The ADU still has to meet your local zoning code. If your town's code does not allow ADUs, this law alone does not change that. Each city and county still sets size limits, setbacks and parking rules. A setback is the required distance from a property line. Towns can also require the owner to live on site. That rule is called owner occupancy. Some places are opening up anyway. Topeka allowed ADUs in its single-family zones in 2024. Sedgwick County voted in September 2026 to allow them by right outside city limits. Kansas City, Kansas, put a citywide ADU rule up for a vote on October 1, 2026. Historic districts are left out of the law. A homeowners association (HOA) rule can still block an ADU. So can a deed restriction, which is a limit written into your property's deed. You may be able to build only if local rules and your property allow it.

The rules at a glance

What to do next

1. Find out whether your property is inside a city or in unincorporated county land, and look up its zoning district.
2. Ask the planning office whether ADUs are allowed in your district and whether the city or county has updated its code for SB 418; many did in 2026 and more are in progress.
3. Submit a complete application and keep proof of the date. If your ADU meets the code, the town has 30 days to approve or deny it (60 or 90 days if a plat is needed), or it counts as approved.
4. Check your HOA covenants, deed restrictions and whether your property is in a historic district; SB 418 does not override any of these.
5. Ask about owner-occupancy rules, size caps, setbacks, parking and rental limits before you design.
6. If your home uses a septic system or private well, talk to the county early about whether it can serve a second unit.

What your town still decides

Kansas zoning powers come from K.S.A. Chapter 12, Article 7, and each city and county still decides whether ADUs are allowed, where, how big, and whether the owner must live on site. SB 418 changes the process, not the rules: once a town's code allows an ADU, a complete application that meets the code must be approved by staff, with deemed approval after 30 days and de novo court review of denials (attorney fees are possible if a town acts in bad faith). Many cities are reading the law to rule out special or conditional use permits for ADUs, so several moved ADUs to by-right approval in 2026: Sedgwick County for unincorporated areas, Roeland Park, and a proposal before Kansas City, Kansas. Others, including Prairie Village, were still studying what the law requires as of August 2026. SB 418 also treats all residentially zoned land inside city limits as zoned for single-family homes, and it does not override HOA rules or deed covenants. A separate 2025 law, the Fast-Track Permits Act (HB 2088, signed April 7, 2025), makes local governments approve or deny a complete building permit application for a single-family residential improvement within 60 days, or it is deemed approved. It is not an ADU law, and whether it covers an ADU building permit has not been tested. A title scan of every 2023-2024 and 2025-2026 bill found no other ADU bill.

Examples of local rules

• Kansas City, Kansas (Unified Government of Wyandotte County): Current code allows ADUs only in narrow cases, such as above a garage in qualifying new construction. In response to SB 418, the City Planning Commission voted 7-0 on September 14, 2026 to recommend an ordinance allowing interior, attached, detached and converted ADUs in any district that allows homes. Per news coverage, units could be up to the larger of 1,000 sq ft or half the main home, no bigger or taller than the house, with no extra parking and approval within 30 days. Both the ADU ordinance and an SB 418 compliance ordinance were on the Board of Commissioners agenda for October 1, 2026; check whether they were adopted. Source
• Sedgwick County and Wichita: Under the shared Unified Zoning Code, an accessory apartment has needed a conditional use permit in the main single-family districts. On September 16, 2026, the County Commission adopted changes allowing ADUs by right in unincorporated areas (Resolution 169-2026). The same draft would let Wichita allow one ADU per single-family or duplex lot. In the city's main SF-5 and TF-3 districts it would need an administrative permit or conditional use (by right in TF-3 when the lot holds a single-family home), with design rules and a 1,000 sq ft cap in the established central area. Water and sewer must be shared with the main house. Wichita City Council had not yet voted. Source
• Topeka: An ordinance passed August 5, 2024, allows ADUs in all single-family zoning districts (R-1, R-2 and R-3), one subordinate unit per zoning lot. Before that, ADUs were allowed only in two-family and multifamily districts. See the city's ordinance and text amendment for size and setback limits. Source
• Overland Park: Ordinance ZRR-3527 (2026) added Chapter 18.376 to the Unified Development Ordinance, restating SB 418's by-right approval for single-family homes, townhouses and ADUs that meet city rules. Whether and how big an ADU can be still depends on each zoning district's rules; for example, the Planned Residential Neighborhood (PRN) district standard (§18.245.050) allows one ADU per lot, at least 400 sq ft and no more than half the main home. Source
• Roeland Park: On August 17, 2026, the City Council approved zoning updates for SB 418 that allow ADUs by right instead of by special use permit and allow single-family homes in all residential zones. Source

What we’re still confirming

• How far SB 418 reaches isn't settled: some cities read it as ending special permits for ADUs, but whether a town can still ban ADUs outright hasn't been tested in court.
• An ADU ordinance was on the Kansas City, Kansas, commission agenda for October 1, 2026, and the outcome isn't confirmed yet.

Laws, bills and citations

This is general information, not legal advice. Your town, village, city or county decides what can be built on your property. If something here looks out of date, email the team.