The Facts

Fortunately we live in a great country that is governed by laws.  The County of Fairfax Zoning Ordinance governing how property is used is very clear.  https://www.fairfaxcounty.gov/planning-zoning/zoning-ordinance

Type of structure

For example, most of the rentals in the County are stand-alone houses.  The first two citations by the County Zoning Administrator were of this type.  The Zoning Ordinance is very specific in its definition of this type of structure.  It is online at the link noted above and comprises 20 articles.  The last article, Article 20, gives definitions in its last part, Part 3.  There are 50 pages of definitions from "ACCELERATION" to "ZOOLOGICAL PARK." Of these 50 pages, page 20 and 21 of this article define 11 terms, all of which include the word "DWELLING." However, only one perfectly defines the stand-alone houses that were cited:  "DWELLING, SINGLE FAMILY DETACHED." It is defined on page 21 of Article 20 of the Ordinance and reads as follows:

DWELLING, SINGLE FAMILY DETACHED:  A single family dwelling unit which is entirely surrounded by open space or yards on the same lot.

Note that the definition uses the term “DWELLING UNIT” which is also defined on the list of definitions in Article 20.  Even though the term “DWELLING“ is defined on the list of definitions in Article 20, IT IS NOT USED IN THE DEFINITION OF THE TERM “DWELLING, SINGLE FAMILY DETACHED” which is the term that applies for the structures cited by the County.

Use of structure

Section 2-502 of Article 2 Part 5 lists the 7 allowed uses permitted for a DWELLING UNIT which, as noted above, is an Article 20 defined term which is used in the definition of a DWELLING, SINGLE FAMILY DETACHED structure.  Family is the first of the 7 permitted uses.

Location of structure

Sections 3-102, 3-202, 3-302, 3-402, 3-502, and 3-802 of Article 3 (Parts 1, 2, 3, 4, 5, and 8 respectively) list the permitted uses in R-1, R-2, R-3, R-4, R-5, and R-8 Residential Districts respectively.  In each case the third permitted use allowed is "Dwellings, single family detached." (The notation "R-2" for example simply means that two DWELLING UNITS are permitted per acre.)

So it is clear, if you have a family residing in a dwelling, single family detached structure in a R-1, R-2, R-3, R-4, R-5, or R-8 Residential District, you have a legally permitted use.  It is as simple as that.  Nowhere does the Zoning Ordinance limit the permitted use based upon the duration of use, only upon the type of structure, the persons occupying the structure, and the District where the structure is located.  The Virginia Supreme Court has supported this position as noted below.