ADU Permits: McKinney vs Plano

Can I build an ADU in McKinney?

McKinney's single-family zoning generally permits only one dwelling unit per lot. An accessory guest house may be allowed as incidental to the main dwelling but cannot be rented as a separate household. A true ADU as a separate rental requires a Specific Use Permit (SUP) with public hearings before Planning & Zoning and City Council.

Are there extra rules for historic downtown McKinney?

Yes. Properties within the Historic Preservation Overlay (HPO) — including downtown, East Side, West Side, and Chestnut Square heritage areas — require a Certificate of Appropriateness from the Historic Preservation Advisory Board before any exterior work or new accessory structure, in addition to the standard zoning and building permits.

Can I build an ADU in Plano?

Plano's single-family zoning generally permits only one dwelling unit per lot. An accessory guest house or servant's quarters may be allowed as incidental to the main dwelling but cannot be rented as a separate unit. A true ADU as a separate rental requires a Specific Use Permit (SUP) with public hearings.

Why is Plano stricter than California cities?

Texas Local Government Code Chapter 211 grants home-rule cities like Plano broad zoning authority and has not preempted local ADU rules. Unlike California's Gov. Code §65852.2, Texas has no statewide ministerial ADU permitting mandate, so Plano retains discretionary control through the SUP process.

What permits do I need?

If allowed as a guest house: a building permit from Building Inspections covering structural, mechanical, plumbing, and electrical trades. For a separate-unit ADU: first a Specific Use Permit through Planning & Zoning, then the building permit. Plano enforces the 2021 IRC with Texas amendments.