Do you need a permit for an AC unit, heat pump, or generator in Fairfax County, VA?
It depends on the details of your project.
AC units, heat pumps, pool pumps and generators may extend 5 ft into a setback but must stay 5 ft from every lot line.
Each unit may be no wider than 10 ft to use the setback allowance.
Heat pumps, AC units and generators are covered by the Chapter 108.1 noise ordinance.
A person last checked these rules on October 20, 2026. This is guidance only, so confirm with Fairfax County before you build.
Check your exact lot
Your zoning district sets the setbacks, and a flood zone can change the permit answer. Enter your address to see both.
Permits a AC unit, heat pump, or generator can need in Fairfax County
| Permit | When it applies |
|---|---|
| Mechanical permit | New heating and cooling systems, and any gas- or oil-fired equipment, need a mechanical permit. |
| Electrical permit | A standby generator and its transfer switch, or a new outdoor unit's circuit, need an electrical permit.Medium confidence |
| Gas piping permit | A gas or propane line needs a fuel-gas permit.Medium confidence |
Limits that apply citywide
| Setback encroachment | Up to 5 ft into a minimum setback, not within 5 ft of any lot line, 10 ft wide max |
|---|
Local details
- Call 811 at least a few days before you dig footings or post holes. Utility locating is free.
- HOA covenants and deed restrictions can be stricter than city rules. Check yours before you build.
How to apply
Common questions
- When does an AC unit, heat pump, or generator need a mechanical permit in Fairfax County?
- New heating and cooling systems, and any gas- or oil-fired equipment, need a mechanical permit. Replacing an electric mechanical appliance in a house is exempt from permit in Virginia (USBC 108.2 item 14.4).
- Where do I apply for an AC unit, heat pump, or generator permit in Fairfax County?
- Apply through PLUS permitting portal, or call 703-222-0801.
Sources
- Virginia USBC, 13VAC5-63-80 Section 108.2, Exemptions from application for permit. Checked 2026-10-23
2. One story detached structures used as tool and storage sheds, playhouses, or similar uses, provided the building area does not exceed 256 square feet... 5. Fences of any height unless required for pedestrian safety as provided for by Section 3306 or used…
- Fairfax County Zoning Ordinance § 5100.2.D, setback regulations (corner lots, sight distance, permitted extensions). Checked 2026-10-21
[Sight distance] Points must be 30 feet from the property lines extended... Sight distance must be maintained between two horizontal planes, one of which is three and one-half feet, and the other ten feet above the established grade... [Extensions] heating,…