Guide · Fairfax County, Virginia · setbacks
How close to the side lot line does Fairfax approve?
When an addition can't meet the side setback, Fairfax owners and builders ask the Board of Zoning Appeals for a reduction. UNDA has read 723 of those requests for additions in the R-1 to R-4 districts since 1995. This is how close the approved ones came to the line.
Precedent, not prediction.
Half of the approved additions sat closer than these distances, and half further away.
Additions
Approvals sit at about half the distance neighbours built at.
The typical approved distance falls as lots get smaller, from R-1 to R-4. In R-3, the median approved addition sat 7.4 ft from the side lot line, and a quarter came within 6.0 ft. On ordinary building permits in R-3, the recorded side setback has a median of 15.5 ft. Denials were rare: 20 of the 723 requests.
| District | Requests | Approved | Denied | Median approved | A quarter within | Neighbours built at |
|---|---|---|---|---|---|---|
| R-1 | 106 | 98 | 3 | 12.6 ft | 10.0 ft | 28.1 ft |
| R-2 | 180 | 167 | 3 | 9.2 ft | 7.5 ft | 19.7 ft |
| R-3 | 325 | 298 | 12 | 7.4 ft | 6.0 ft | 15.5 ft |
| R-4 | 112 | 103 | 2 | 6.3 ft | 5.0 ft | 11.5 ft |
Board of Zoning Appeals cases with a side setback request for an addition, decided 1995–2026. Approved includes approved in part; the rest were withdrawn or have another outcome. Median and quarter are of approved cases with a recorded distance. Neighbours built at: median side setback recorded on Fairfax building permits in the same district (R-1 1,407 permits, R-2 1,219, R-3 2,361, R-4 1,007).
Other structures
Decks, carports and sheds come closer.
Smaller and open structures were approved nearer the line than additions. These are the districts with at least ten approvals to go on.
| Structure | District | Requests | Approved | Median approved | A quarter within |
|---|---|---|---|---|---|
| Deck | R-1 | 39 | 35 | 9.9 ft | 6.3 ft |
| Deck | R-2 | 33 | 30 | 8.7 ft | 4.2 ft |
| Deck | R-3 | 47 | 46 | 5.0 ft | 2.0 ft |
| Deck | R-4 | 14 | 11 | 3.8 ft | 2.1 ft |
| Garage or carport | R-3 | 33 | 30 | 3.8 ft | 2.9 ft |
| Shed or other accessory building | R-1 | 69 | 61 | 8.6 ft | 4.5 ft |
| Shed or other accessory building | R-2 | 33 | 26 | 5.2 ft | 2.7 ft |
| Shed or other accessory building | R-3 | 78 | 70 | 3.8 ft | 2.1 ft |
| Shed or other accessory building | R-4 | 51 | 42 | 2.4 ft | 1.4 ft |
Same source and method as above. Smaller accessory structures may not need Board approval at all; the county's own guidance sets out when they do.
How to read these numbers
What this shows, and what it doesn't.
- It's what the Board approved, not what it will approve.Each case turns on its own facts: the lot, the existing house, the neighbours and the evidence. A distance that was approved before is precedent to cite, not a promise.
- Only cases that reached the Board are counted.Many owners redesign or never apply, so the approval rate reflects requests that were judged worth making.
- Your district's standard comes first.Minimum side setbacks differ by district and by lot type, including cluster lots. Where a case record gives no zoning, UNDA uses the parcel's current zoning. Check your lot with the county before relying on any figure here.
- One distance per case.The record holds one side distance per case, so where a case covers more than one structure it may describe only one of them. Some cases are recorded at 0 ft where the Board's text gives another figure, so this guide shows the median and the closest quarter, not the minimum.
Source: Fairfax County Board of Zoning Appeals case records and minutes, read by UNDA. The Board's minutes are read for Jul 1995–2013 and 2023–26. Figures as at 6 November 2026. UNDA does not publish the names of property owners or applicants.
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