Fairfax County is changing its rules and regulations governing decks, porches, patios and gazebos as well as chimneys and bay windows to do away with what some builders and county staff members have called "confusing mumbo jumbo."

Under the old rules, it was unclear which applied to decks or porches and which covered terraces or decks and porches. "There were two sets of regulations on decks," confusing both builders and building inspectors over who was to determine which set of rules governed which deck, one county staff member explained. One regulation setting standards for decks also covered chimneys and bay windows.

"Terraces were treated different from porches while bay windows, chimneys and decks were treated alike in another section," according to a staff report on the changes.

The Fairfax Board of Supervisors recently eliminated dual rules and established new rules for chimneys, bay windows and other parts of a house that intrude into the yard.

"Whatever you are building, whether it is a balcony, a portico, a porch, a gazebo or a deck, it is now a deck," according to Lu Wright of the county's zoning administrator's staff.

County staff members, supervisors, builders and residents agreed that something needed to be done to clarify the confusing rules. Changes were supported by the Board of Zoning Appeals, which must act on the applications for variances and special permits dealing with decks.

The new rules tighten guidelines for intrusions of decks into side and front yards, but relax standards for decks in back yards.

The new regulations allow decks and porches to extend 12 feet into the required back yards of single-family detached homes. But they also make it easier for homeowners and builders to get permission from the county to extend decks and porches beyond the 12-foot limit.

According to Wright, those who want to go beyond those limits will now have to go to the Board of Zoning Appeals for a special permit. Previously, those seeking exceptions had to ask that board for a zoning variance, a much more legally complicated process than that required for getting a special permit in Fairfax, an attorney explained.

Although the county staff had recommended limiting extensions into back yards to 10 feet, the supervisors voted to go along with a plea from the Northern Virginia Builders Association for the 12-foot limit.

"We believe the extension of 12 feet would provide current homeowners the flexibility to construct decks onto their homes which will accommodate their personal needs while not intruding on the aesthetics of the neighborhood," Bradley Crockett, a representative of the builders' group, wrote in a letter to the board. He said the extra two feet would be "especially beneficial to households where there are disabled residents who must rely on wheelchairs."

The 12-foot limit will allow for construction of reasonably sized decks on houses located only 25 feet from the rear lot line in most single-family detached zoning districts. Under the new regulations, decks with roofs or porches will not be allowed to extend into minimum required front or side yards without special permits.

The new regulations apply to single-family detached and attached housing as well as to multiple family housing units in commercial buildings. But the rules for each differ.

The new rules prohibit the Board of Zoning Appeals from granting permission for a deck or porch that would cover more than 50 percent of a back yard. However, in some cases in which yards virtually have been eliminated in attached-housing developments, the rules "limit any deck or porch to 50 percent of whatever land is left there," Wright explained.

New rules governing chimneys, bay windows and other structures that extend into yards now will have their own category with specific regulations in the county building codes.

"The same rules that did apply to decks and chimneys will no longer apply to bay windows," said one county staff person.