Fairfax County claimed more than half of the new commercial construction space started in the Washington metropolitan area in recent months, a record amount that bolsters the jurisdiction's reputation as the economic engine of Northern Virginia.

More than 8.6 million square feet of commercial space in 117 projects was started in the Washington region from July through September, with Fairfax accounting for 4.7 million square feet, according to a study released yesterday by the Metropolitan Washington Council of Governments.

Jurisdictions outside the District contributed about 90 percent of the total commercial development. Northern Virginia and suburban Maryland started 109 projects totaling 7.8 million square feet.

The report provides further evidence of the Washington region's evolution from a center of government to one with a multitude of service industries. Commercial space is defined as including retail, mixed-used or other types of nonresidential construction.

Fairfax County has consistently led area jurisdictions in both the size and number of new commercial projects. This time, more commercial construction was started in the county than during any other quarter since 1980, when COG began keeping track of construction, according to COG's Vetoria Alston.

County Executive J. Hamilton Lambert said "it was predictable that we were going to have this large amount because of what had been in the development pipeline . . . . It is primarily related to a number of large corporation projects coming on line."

The region's commercial development is concentrated in Tysons Corner, Herndon and the Dulles area in Fairfax County; along the I-270 corridor skirting Gaithersburg and in Bethesda and Chevy Chase in Montgomery County, and along I-95 and Rte. 50 and in Greenbelt in Prince George's County.

Northern Virginia builders said they saw no connection between the surge in construction starts and the high-profile election for chairmanship of the County Board of Supervisors. The contest was regarded by many political supervisors as a referendum on the county's pace of growth.

Jay Feldman, with the Northern Virginia Building Industry Association, a 1,500-member group based in Fairfax, said, "Even with the race looming and, supposedly, the fear that {a change in county leadership} would lead to a slowdown, it costs money to build all of the square footage."

The construction starts came prior to the Wall Street crash on Black Monday, Oct. 19. If the stock market problems affect development activity, that would show up during the fourth quarter of this year, COG said.

According to the study, Fairfax was followed in the number of commercial projects started by Montgomery County, with 1.1 million square feet, and Prince George's County, with 1 million square feet. The District started about 808,000 square feet; Fairfax City, 620,000 square feet, followed by Prince William, Loudoun and Arlington counties.

Developers built 17 percent of commercial space around planned or existing Metro stations, according to the report. The area around the McPherson Square Metro station in downtown Washington had the largest share of the development during the study period, with 675,000 square feet of office space in two buildings under way. The Silver Spring and Franconia/Springfield Metro stations ranked second and third, with a new office building and two warehouses, the report showed.