The D.C. Zoning Commission voted yesterday to remove a limitation on the size of structures to be used for apartments and condominiums in the heart of the city's major commercial areas.

The five-member commission acted to change existing zoning laws, which now allow buildings in commercial areas to be bigger if they are used only for office space.

"The policy objective is to encourage on the fringes of downtwon and in downtown itself residences so you have more life after 5 (p.m.) and on weekends," a high-ranking city official explained.

The changes, which the commission adopted by a 3-to-0 vote, now go to the National Capital Planning Commission. Zoning Commission member Theodore F. Mariani abstained from voting and Ruby McZier was absent.

If NCPC, a federal agency, does not object to the revisions within 30 days they will go into effect.

"Our clients will be giving serious attention to residential development in office districts," if the changes become effective, said Charles S. Wilkes, an attorney with the law firm of Linowes and Blocker.

The law firm handles many zoning cases in the city and has been active in redevelopment plans for downtown.

Under current zoning laws, developers can build apartments in the city's busiest in the same area can be one-third larger than an apartment building.

But in other, smaller commerical areas, such as Tenley Circle in Northwest and Minnesota Avenue in Northeast, developers would be better off financially to mix business and residences in the same building, under terms of the commission's actions yesterday.

The developer must mix the commercial and residential used in these areas to gain the right to build to the maximum amount of square footage allowed in these zoning districts, under the commission's proposals.

"The commission is trying to meet the housing crisis in the city without injuring severely the office and commercial base of the city," a knowledgeable observer said yesterday after watching the commission's actions.