This month's election for Gaithersburg mayor and City Council will have familiar names on the ballot: all incumbents.

Mayor Bruce A. Goldensohn and council members Sidney A. Katz and Gertrude (Dolly) M. Kildee have no challengers in their reelection campaigns. They are seeking four-year terms in city elections April 26.

The terms for the other council members--W. Edward Bohrer Jr., Julius J. Persensky and Mary B. Ward--continue until 1984.

In an attempt to allow for orderly development, the mayor and council last week created special zoning categories designed to separate residential and commercial areas.

Two buffer zones city planners say will insulate commercial and residential districts will be included in a revised city development plan the council is expected to adopt in June, according to Don Stickle, a city planner.

Under the proposed design, a "commercial buffer zone" would scale down business activities and introduce multi-family housing by blending flower shops, laundries and gift stores with apartment buildings and duplexes, Stickle said.

A "residential buffer zone," he said, will screen out businesses further, allowing only barbershops, cosmetology salons, day-care centers, publicly owned establishments and professional offices.

While the downtown business district and the outlying residential neighborhoods would be separated by the two buffers, Stickle said, patches of commercial establishments and houses along Rte. 355 in Gaithersburg would be separated by only the residential buffer zone.

Planners are preparing a new comprehensive zoning plan for the city, scheduled to be brought to the council for approval sometime this year, Stickle said.

The council once again put out to bid a contract to restore a one-block stretch of downtown storefronts. The council awarded a $31,500 contract last month to Bradley Construction, a city contractor, only to discover that the labor wage limits the city advertised were lower than allowed by the federal Department of Housing and Urban Development, which is financing most of the project through Community Development Block Grant funds. Wary of possible legal tangles, the council decided to rebid the project, according to City Administrator Sanford Daily.

Jeffrey S. Topley and Anne Cleary were appointed to the city Beautification Committee, filling two vacancies on the eight-member panel.

The council also hired Deneau Construction Inc., a city contractor, to put up a shelter that will house restrooms, a concession stand and a storage room at Rabitt Park, the site of football, baseball and soccer fields, a city spokeswoman said. The price: $54,200.

Another firm the council hired--Deloitte, Haskins & Sells of the District--will audit the city's financial books from this year until 1985 for a fee of $16,500.