Next summer the Brotherhood of Railway and Airline Clerks, a 250,000-member union with a staff of 105, will move to Montgomery County from Chicago, where it has been operating out of a building near O'Hare Airport.

The union, which will continue to house a 10-member legislative affairs staff in the AFL-CIO building north of the White House, plans to set up its main shop in a new, $1.7 million building north of Rockville in the growing light industry corridor along Route I-270.

The clerical union's move from the Midwest to the national capital is part of an increasing surge of associations, business headquarters and other groups into this area.

"Essentially, we see much of our work as being with the regulatory bodies based in Washington - and to some degree with the Congress and Amtrak - and Courail in Philadelphia," said Richard I. Kilroy, the unions's international vice president for administration. "And we also have a new president, Fred J. Kroll, who lives in Philapelphia. With the new leadership, we also wanted a new look for our union that has roots tracing back to 1885, when members were mostly railway telegraphers. It grew from there."

As things happen in the world of commerce, it became known that the BRAC was thinking about relocating to Washington. Leasing specialist Harry P. Galentine Jr., of the Weaver Bros. realty brokerage and mortgage banking firm, who earlier this year was involved in working out a new site and lease for Amtrak here, got the word.

"I made a contact and showed the BRAC some sites in downtown Washington, which is my beat," he recalled the other day. "But the more we talked the more I got the feeling that this union would like to have its own identity and building."

That's when Galentine went to James W. Kibbe, who heads commercial sales for Weaver Bros. "Normally, we do different things," said Kibbe," but in this instance Harry saw an opportunity for our firm to make a deal outside his field and in mine. I knew that the 41,500-square-foot building built by Furman Builders would be available. Then we worked in conjuction with the Whiston Group, a Chicago cago firm that represented BRAC, and, after the usual negotiating, the sale was made."

Between now and next August, the BRAC will have the interior of the building at 3 Research Blvd. finished to its specifications.

"All of our 105 employees have been invited to make the move with us," Kilroy said, "and we expect that at least 80 will relocate. Some have mates whose jobs make the move unfeasible."

Kilroy said the union Maryland because of the right-to-work laws in Virginia. He added that he and other top officers felt assured that the staff would be able to find suitable housing and have plenty of free parking near the new office, which is located west of the Shady Grove Road exit of I-270.

The rising cost of new office space in downtown Washington was also cited as a factor in the choice to buy a suburban site. In the Chicago area, the Railway and Airline Clerks owned a seven-story building and occupied two floors, leasing the rest. That building was sold for approximately $6 million to a tenant.

"We wanted to get out of the landlord business and have a building just for us," Kilroy said.

Speaking for the Rockville-based Furman building firm, marketing director Thomas Poe said that the market for speculative buildings - constructed without a specific buyer or tenant in mind - has been strong in the I-270 corridor. He said the proliferation of research and development and light industry buildings in the Shady Grove area is due largely to government contractors but he pointed out that varied businessess are also gravitating to the area.

Kibbe recalled selling several large tracts in 1956 to Sam Eig, who began development in that area with his Washington motel. That complex has been expanded over the years to include two golf courses, a high-rise apartment building and the-ater-in-the-round.

Since then, Vitro Laboratories, IBM, Nus, NCR and Bechtel Power corporations, the Bureau of National Affairs publishing company, General Motors and others have located in the area. Montgomery County also put its police academy there and has land for other facilities. Three new restaurants - Vallees's, Red Lobster and Victorian Station - also chose that location.

On an overall basis, the light industrial and office-warehouse space in this area now totals about 80 million square feet, according to a 1977 survey made by the Coldwell Banker real estate firm.

"The size of the industrial data base in this area, based on our verified research, was larger than anticipated for this predominantly white-collar area," noted James B. O'Brien, vice president and resident manager of the firm.