Westminster ADU Zoning Rules & Permit Guide

ADU Regulations in Westminster, Colorado

Spanning Adams and Jefferson counties, Westminster regulates ADUs entirely through its own municipal zoning code. With no Colorado statewide ADU mandate, the city's minimum lot size and owner occupancy rules are final authority.

Below is a summary of the key zoning rules applicable to Accessory Dwelling Units in Westminster as of 2026. Regulations are governed by local zoning ordinances, as Colorado has no statewide ADU mandate (HB 24-1152 addresses transit density).

Additional Local Requirements for Westminster

• ADU on lots 5,000 sq ft minimum
• Minimum 200 sq ft
• Owner occupancy mandatory
• Building permit required — CO has no state ADU mandate

Frequently Asked Questions About ADUs in Westminster

Can I build an ADU in Westminster?

Westminster allows ADUs in certain residential zones. Contact the planning department to confirm your zone eligibility.

How big can my ADU be in Westminster?

What is the maximum ADU size allowed in Westminster? ADUs in Westminster can be up to 1,000 square feet, subject to the property's zoning and lot coverage limits. Always confirm the exact allowed size with the Westminster planning department before designing your project.

What about setbacks and other requirements in Westminster?

What are the setback requirements for an ADU in Westminster? ADUs in Westminster generally require setbacks of 5 ft rear, 5 ft side. California state law (AB 68) limits local setback requirements to 4 feet for existing structures, but always verify with local zoning.