The Village of Mount Horeb passed its first ADU ordinance in March 2026 — a meaningful change for homeowners who've been waiting to add a second unit. For the first time, Mt Horeb residents can build a permitted Accessory Dwelling Unit on a single-family or two-family residential lot.
This is good news. But like most new ordinances, it comes with specific requirements that differ from what you'll find in Madison, Fitchburg, or Middleton. Before you start planning, there are two things every potential ADU owner in Mt Horeb should understand clearly.
What the Ordinance Allows
Under the new Mt Horeb ordinance, homeowners on qualifying lots can build a detached, attached, or garage ADU. The basic parameters:
- Maximum size: 800 sq ft, or 50% of the primary dwelling — whichever is less
- Setbacks: 5 feet from rear and side property lines
- Rental: Permitted. You can live in the main house and rent the ADU, or vice versa
- ADU types: Detached, attached, and garage ADUs are all permitted
The Owner-Occupancy Requirement Is a Recorded Covenant
Most municipalities in Dane County require owner-occupancy as a permit condition — in Madison or Fitchburg, this is typically self-certified at application. Mt Horeb is different. The ordinance requires a recorded covenant with Dane County that runs with the land. If you sell the property, the new owner inherits it. Consult a real estate attorney if you plan to sell within 5–10 years.
The Height Formula Is Non-Standard
Most Dane County municipalities set a straightforward maximum height. Mt Horeb's ordinance uses a pitch-based formula instead — allowable height is calculated relative to roof slope. This requires early coordination between site analysis and architectural design.
What to Do If You're in Mt Horeb
The ordinance is new and we're ready to build under it. Start with a free feasibility check — we'll confirm your lot qualifies, walk through the covenant, and tell you exactly what's possible.