Montgomery County Executive Charles W. Gilchrist, accelerating efforts to relieve traffic congestion in the upper parts of the county, proposed $89 million in new road projects yesterday along the I-270 and Rte. 29 corridors. He also recommended levying fees on builders of new homes and office buildings to help pay for the roads, as well as selling more county-backed bonds.

The new projects, designed to open areas of the county currently under a moratorium on new development, signaled a major expansion in the county's already ambitious road building program and a desire to go beyond current efforts to catch up with traffic congestion.

"These groups of projects in the two corridors would get us ahead of the power curve for the first time, and get the roads under way before we have congestion," said county Transportation Director Robert J. McGarry.

As part of a two-pronged program to relieve congestion and fix "a broken planning process," Gilchrist also announced a number of short-term transportation initiatives, including free rush-hour bus service in the two corridors and legislation to strengthen the executive's role in the planning process.

The program, presented at a news conference with an extensive backdrop of charts and maps, provides an alternative to legislation proposed by Gilchrist's political rivals on the County Council who would like to curb the county's development boom for up to three years until new roads can be built. The council bills are aimed at some 46,000 proposed residences that already have already been approved for construction and thus don't fall under the county's current moratorium.

"The two-part approach to our problem is much more steady and appropriate way to go than to take panic measures . . . to put artificial caps on development," the executive said, alluding to the council measure. "There have to be steps taken to avoid this panicked approach."

The county is in the midst of a development boom that has fueled the construction of thousands of new homes and office buildings during the last few years.

The rapid pace of development has outstripped county and state construction of new roads and road improvements, causing unprecedented traffic jams in fast-growing areas of the county, such as Germantown, Gaithersburg, White Oak and Cloverly.

To catch up with current development, the executive last year proposed a six-year road construction program that called for the acceleration of some projects that had been on the drawing boards for years.

The package proposed yesterday would go beyond even those efforts, adding eight new road projects to the capital improvements program for the fiscal years 1987-92.

More than $57 million in projects in the Germantown area would include a $30 million interchange at Germantown Drive and I-270; the $3.4 million expansion of Crystal Rock Drive between Germantown Drive and Rte. 118; a $7.5 million Germantown-Montgomery Village connector and a $10.8 million relocation and expansion of Rte. 118.

The county also would spend $32 million in the Rte. 29 corridor to improve traffic capacity and to add a "people moving option" that will include a mix of free and express bus service from the Howard County line to Silver Spring, according to officials. Free bus service, which also will be added during rush hours on routes from Germantown to the Shady Grove Metro Station and to the B&O railroad station, will cost $1.1 million a year, according to McGarry.

To help pay for the projects, the county would impose a fee of up to $1,200 per house and $2,400 per thousand square feet of office space. The fees would be collected from developers, who will be free to pass them on to homebuyers.

The money would be earmarked solely for road projects in the area where the developer plans to build, the executive said. The fees would be set to raise half the cost of major arterial highway improvements in each of the affected areas, according to a memorandum.

In addition, the county intends to increase the amount of its bonded indebtedness from $385 million to $510 million during the next six years. The increase is well within the limits suggested by an advisory report and by consultants to retain the county's coveted AAA bond rating, Gilchrist said.

Earlier this year, the Suburban Maryland Building Industry Association voted to oppose fees as a solution to the road crisis, and yesterday F. Hamer Campbell Jr., the group's director of legislative and government affairs, reiterated that position.

"We will be looking at the situation again, but philosophically, we're opposed to anything like impact fees that penalize the new homeowner for facilities that serve the entire county," he said. "I do not foresee the industry as a whole absorbing these costs."

Some of the proposals announced yesterday would require state legislation to implement, while others would require council approval.