How Herndon Handles Accessory Structures: A Practical Guide

Herndon maintains 64 local ordinances across all categories, and 3 of those deal specifically with accessory structures. Here is a breakdown of what the city actually requires, what is prohibited, and where Herndon falls on the strict-to-permissive spectrum compared to other cities.

Shed Rules

In Herndon, sheds 256 square feet or smaller and one story do not require a building permit under the Virginia USBC, but still must comply with zoning setbacks. Sheds over 256 sq ft require a building permit. All sheds must respect property lines, typically with minimum setbacks of 5 feet from side and rear lot lines, and comply with lot coverage limits and HOA rules.

Key details: Fact: Sheds up to 256 sq ft and one story exempt from building permit. Fact: Sheds over 256 sq ft need full building permit. Fact: Typical setbacks: 5 ft side and rear; no front yard. Fact: Max height usually 15 ft; subject to lot coverage limits. Fact: Electrical permit required if shed has power; HOA approval often required.

Contact your local code enforcement office for specific penalty information.

ADU Rules

Herndon permits accessory dwelling units (ADUs) in certain residential districts with a special exception or by right depending on zoning. ADUs must be subordinate to the primary dwelling, have a separate entrance, and comply with parking and owner-occupancy requirements. Virginia encourages but does not mandate ADU approval under VA Code §15.2-2292.1.

Key details: Fact: ADUs permitted in certain residential districts, some by special exception. Fact: Owner-occupancy required (primary or ADU). Fact: One ADU per lot, subordinate size to primary (often 35% or 800-1000 sq ft). Fact: Separate entrance, kitchen, bathroom required. Fact: HOAs frequently restrict or ban ADUs independently.

Contact your local code enforcement office for specific penalty information.

Garage Conversions

Converting a garage to living space in Herndon requires a building permit, compliance with the Virginia USBC for habitable space, and zoning review. Converted space must meet egress, ceiling height, ventilation, and insulation standards. Required off-street parking typically cannot be eliminated, so conversions often need replacement parking. HOA approval is commonly required.

Key details: Fact: Building permit required for all garage conversions. Fact: Must meet USBC habitable space standards: 7 ft ceiling, egress windows, insulation. Fact: Parking requirement typically cannot be eliminated without replacement. Fact: If adding full kitchen, treated as ADU with additional requirements. Fact: HOA approval commonly required; unpermitted conversions cause sale issues.

Contact your local code enforcement office for specific penalty information.

The Bottom Line

Herndon'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 Herndon is broadly strict or permissive.

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