Hillsboro's Accessory Structures: The Rules That Matter

Every city handles accessory structures a little differently. In Hillsboro, Oregon, there are 4 distinct rules that residents and property owners should be aware of. Some are stricter than what neighboring cities enforce, and others are more relaxed. Here is what you need to know.

Carport Rules

Hillsboro treats a carport as an accessory structure under Community Development Code Section 12.40.104. In residential zones, side and rear setbacks may be reduced to three feet for an accessory structure meeting Subsection 12.40.104.B. Setbacks are measured to the support posts closest to the driveway, or to the roof edge.

Key details: Accessory Code: CDC 12.40.104. Setback Code: CDC 12.50.130. Min Side/Rear Setback: 3 feet (residential). Setback Measured To: Posts or roof edge. Building Code: Oregon Residential Specialty Code.

Constructing a carport without a Hillsboro building permit, placing one within three feet of a lot line, or missing principal-structure setbacks for an attached carport violates CDC 12.40.104 and 12.50.130. Code Compliance may issue stop-work orders under HMC 4.04.

ADU Rules

Hillsboro allows ADUs on all single-family lots per Oregon HB 2001. ADUs are capped at 800 square feet. Both attached and detached types are permitted.

Key details: Allowed: One per single-family lot. Size Cap: 800 square feet. Types: Attached or detached. State Law: Oregon HB 2001.

Unpermitted ADUs face enforcement. Non-compliant structures must meet code.

Garage Conversions

Garage conversions in Hillsboro require building permits. If creating an independent unit, it may qualify as an ADU under Oregon law.

Key details: Permit: Required. Code: Must meet habitable space standards. ADU: May qualify under Oregon law. Parking: Replacement generally not required.

Unpermitted conversions face enforcement action.

Shed Rules

Small sheds under 200 square feet generally do not need permits in Hillsboro. Larger structures require permits and must meet setbacks.

Key details: No Permit: Under 200 sq ft. Permit Required: 200+ sq ft. Setbacks: Must comply. Easements: Cannot build in.

Unpermitted large structures must be retroactively permitted or removed.

Hillsboro is more permissive than most cities when it comes to shed rules. That said, there are still limits.

The Bottom Line

Hillsboro's accessory structures rules are a mixed bag. Some areas are strict, others are relaxed, and the details matter. The best approach is to check the specific rule that applies to your situation rather than assuming Hillsboro is broadly strict or permissive.

These rules come from Hillsboro's publicly available municipal code. For complete penalty schedules, exemption details, and answers to common questions, see the individual ordinance pages throughout this guide.