6\u201310 weeks
UGA permit timeline
8\u201312 weeks
Rural permit timeline
First: Determine Your Location
The county permit process depends on whether your property is inside an Urban Growth Area (UGA) or in a rural area. This determines which rules apply, what additional reviews are needed, and what infrastructure requirements exist. For the full regulatory breakdown, see our Whatcom County ADU rules guide.
Urban Growth Area (UGA)
- More permissive ADU rules
- Usually connected to sewer
- Faster permit timeline
- Two ADUs per lot allowed
Rural Area
- 4.5+ acres typically needed
- Septic/well may need upgrades
- Health Dept review required
- Longer permit timeline
Not sure? Our free feasibility study checks automatically using GIS data.
UGA Permit Process
Zoning & Feasibility Review
- Confirm property is in UGA (not Lake Whatcom Watershed or excluded zone)
- Verify lot size meets minimum for zoning district
- Check for critical areas (wetlands, streams, habitats)
- Review setback and lot coverage requirements
Design & Engineering
- Prepare site plan with ADU placement and setback dimensions
- Create architectural drawings (floor plans, elevations)
- Complete structural engineering (if required)
- Prepare stormwater management plan
- Get site survey if property boundaries are unclear
Pre-Application Conference (Recommended)
- Schedule meeting with Whatcom County PDS
- Present preliminary plans and get feedback
- Identify any issues before formal submission
- Learn about specific requirements for your parcel
Submit Application
- Complete county permit application forms
- Submit all required documents and plans
- Pay application fees
- Provide proof of water and sewer connection capacity
County Review & Permit Issuance
- Planning division reviews for zoning compliance
- Building division reviews construction plans
- Address any correction requests promptly
- Receive building permit and begin construction
Additional Steps for Rural Properties
Rural properties have extra requirements beyond the standard UGA process:
Septic System Review
Whatcom County Health Department must review septic capacity. Existing systems may need upgrade or replacement ($15,000–$30,000). See our full permit cost breakdown for details.
Well Water Assessment
If on well water, ensure adequate capacity for an additional dwelling unit. May need water rights review.
Critical Areas Assessment
Rural properties are more likely to have wetlands, streams, or steep slopes. A Natural Resources Qualified Consultant assessment may be required.
Road Access Review
Ensure the property has adequate road access for an additional dwelling. Fire department access requirements apply.
County permitting involves multiple departments. Our ADU permitting service coordinates with Planning, Building, and Health departments on your behalf — $1,500 deposit, applied to your project cost. See our full cost breakdown for the complete investment picture.
Whatcom County Planning & Development Services
Phone: (360) 778-5900
Email: [email protected]
ADU page: whatcomcounty.us
GIS: County GIS Maps
Last updated: March 2026. Not legal advice. Verify current requirements with Whatcom County PDS.
Let Us Navigate County Permitting for You
Our $1,500 permit package handles all zoning verification, documentation, and county coordination.
Start Your Permit Package
