Development of a $35 million complex of commercial, office and residential properties is scheduled to begin this fall on 56 acres of woodland in the small city of Manassas.

The site is bounded by Sudley Road (Route 234) and Plantation Lane and faces the Prince William County Hospital.

Called the Villages of Manassas, the project will be developed by Manassas Forum Associates, a limited partnership of ASB Manassas Venture Corp., a subsidiary of American Savings Bank of New York, and managing general partners Henry A. Long and P. Wesley Foster Jr.

Long and Foster are partners in a nine-year-old real estate firm bearing their names that has one of its offices in Manassas.

Long said the first construction on the former Henry Burba estate, which was purchased in 1974 for about $1.6 million, will include 284 garden apartments.Designed by the Kohler-Daniels architecture firm, the apartments will resemble town houses with varied rooflines, Long said.

Thomas P. Harkins, Inc., a Silver Spring construction company will build the apartments, which may be subsidized under the federal 22(d)(4) mortgage interest program, Long said.

Site plans, which include a small lake and recreation area, call for 55,000 square feet of office space and 55,000 square feet of small shops to be built in a small "village" with walkways and courtyards. Specialty shops and professional and service tenants are expected to predominate.

Plans also call for "cluster" houses and, subject to approval by the Manassas City Council, town houses. While moderate-price town houses have been heavily built in the Manassas area in recently years, the need for moderate-range rental housing has been regarded as stronger.

Long said that the recently incorporated city has developed an increasingly strong economic base and added that the area is expected to offer employment for some 40,000 workers by 1980. IBM, a principal employers in recent years, has about 3,500 on its payroll there.

Manassas is clearly shedding its image as a sleepy hamlet and becoming a bedroom community for Washington workers, Long added.

Manassas Junction, scene of the Battle of Bull Run in the Civil War, was rebuilt and incorporated as a town called Mannasas in 1873. It now has a population of 55,000 and nearly 200 working farms.

The Manassas Battlefield Park attracts hundreds of thousands of visitors annually.

The Woodbridge, Va.-based home building firm of Cecil D. Hylton constructed many single-family houses near Manassas. One of the Washington area's first fast-selling, low-priced town house projects, Georgetown South, was built in this part of Prince William County. It began to attract more builders and buyers after the Route 66 connection to the Washington Beltway was completed a decade ago.

C. M. Moyer Jr., Manassas city manager, said the city is currently experiencing "another burst of growth."