The majority of American renters surveyed recently said they would like to own a house but cannot afford to buy one, according to the National Association of Realtors.

John Tuccillo, NAR's chief economist, said members of 3,200 households, both renters and homeowners, answered questions intended to determine the differences between those who own their homes and those who rent.

Half of the renters said they would like to own the next house or apartment they moved to if they could afford it, and another 25 percent said they would eventually like to own a home, if not the next place in which they live. Only 18 percent said they had no desire to own a home.

Asked why they did not buy a home, 70 percent of tenants in the survey said they could not afford to make the down payment. A total of 47 percent said home prices were too high, 45 percent did not buy because they liked their rental situation, and 30 percent said they could not afford the monthly mortgage payments and home maintenance costs. The numbers do not add up to 100 percent because some respondents gave more than one reason for not buying.

Many families said two incomes made the difference in whether they could stay in the homes in which they currently live.

Of the homeowners, 70 percent said they would be able to stay if the smaller income were lost and 50 percent said they could remain in their present home if the larger paycheck stopped. Of renters, 80 percent said they could stay in their homes if the smaller income stopped and 60 percent if the larger income were the one to go.

There has been a "distinct decline in home ownership in the last six or seven years," Tuccillo said, with the biggest percentage of the drop occurring among young families and individuals. In the past, this group has accounted for one-third of all sales to first-time home buyers, or more than 1 million sales a year, Tuccillo said.

The "leap from renting to owning your own home is not as easy as it once was" for young, first-time home buyers, Tuccillo said. During the late 1970s, housing prices went up faster than incomes, and the gap widened.

The major barriers to young, first-time buyers being able to afford homes are high prices and high interest rates that drive up monthly mortgage payments, and the lack of capital to make a down payment, the NAR said.

Tuccillo said some kind of tax incentives or a loan program are possible solutions for helping financially strapped families and individuals buy homes. He said any solution "must be led" by the federal government. The Washington area commercial office vacancy rate inched upward to 13.4 percent in the July-to-September period from 12.9 percent in the second quarter, according to a new survey by the Spaulding & Slye commercial brokerage firm.

The downtown vacancy rate dropped from 11.5 percent to 9.2 percent, the firm said, while the suburban Maryland rate jumped from 12 to 15.7 percent and the Northern Virginia rate rose from 15 to 17 percent.

Spaulding & Slye said Alexandria's vacancy rate remained about the same at 20 percent, while the Arlington rate jumped to 16.2 percent, the highest rate in a decade. Fairfax County's vacancy rate was 17.3 percent, Montgomery County's rate hit a new high of 16 percent, and Prince George's County was 15 percent. IN THE BUSINESS ... William H. Doggett, who runs a Bethesda architectural firm that bears his name, will be installed Oct. 23 as the new president of the Washington Building Congress ... Randall W. Byrnes, Spaulding & Slye's senior vice president and Washington regional manager, has been elected the 1987-88 president of the Northern Virginia chapter of the National Association of Industrial and Office Parks ... Kenneth Allen Co. has opened its fourth residential community, Westwind Forest in Woodbridge ... The Investment Group Development Corp. has bought the Reston/Herndon Centre, a two-building office complex in Herndon, from 606 Associates ... Amurcon Corp. of Virginia has started work on the 105-unit Sommerset retirement community in Sterling ... City Sites Inc. and Barbara Held Inc., two real estate firms, have merged, with the new firm called Barbara Held/City Sites Real Estate Inc. ... Cambridge Development Co. of McLean has started work on the 23-acre Ammendale Business Campus at 6500 Virginia Manor Rd. in Beltsville, which eventually will have 300,000 square feet of office, research and development and distribution space ... Park Tower Realty Corp., a major New York developer, has opened an office here and has appointed Thomas J. Regan, formerly executive director of the Pennsylvania Avenue Development Corp., as its head. The firm's first Washington project will be a 250,000-square-foot office tower designed by I.M. Pei and Partners at 1001 19th St. in Rosslyn ... Eugene F. Krebs, former principal broker at Krebs and Daughters Realty in Riverdale, has been elected president of the Prince George's County Board of Realtors. The board has also named James J. Fischetti, principal broker of RE/MAX One of Laurel, as its Realtor of the Year ... The Fairfax chapter of the National Association of Independent Fee Appraisers is sponsoring a course on residential real estate appraising Nov. 5-7 at the Loudoun County campus of Northern Virginia Community College. More information is available by calling (301) 631-1288 ... Ruxton Homes Inc., a Northern Virginia builder, has started work on its newest subdivision, Ruxton at Dale View in Dale City ... Robert M. Bass, one of the wealthy Bass brothers of Fort Worth, was elected chairman of the National Trust for Historic Preservation at the group's annual conference here last week ... Roulac's Strategic Real Estate newsletter says a survey by its consulting group shows that 10 leading insurance companies owned or controlled more than $164 billion worth of real estate equity or debt as of the end of 1986. The five biggest are Prudential Insurance Co. of America, Aetna Life & Casualty Co., Equitable Life Assurance Society, Metropolitan Life Insurance Co. and Travelers Insurance Co. ... The Virginia Department of Commerce and the State Board for Contractors have revoked the licenses of four builders, including Patricia Martz, doing business as Martz Home Improvements of Fairfax. The action was taken as the result of claims filed by customers against the Virginia Contractors Transaction Recovery Fund. Under Virginia law, if a customer obtains a legal judgment against a contractor and the contractor fails to pay the judgment, the customer can file a claim against the fund for full or partial reimbursement. If a payment is made from the fund, the contractor's license is revoked until the fund is repaid in full ... Horizon Development Corp., Winchester Homes and Carbone Enterprises have bought 115 acres of residentially zoned lane in Prince William County near routes 1 and 234 for a new development called Princeton Woods ... W.C. & A.N. Miller Realtors is celebrating its 75th year in business and recently opened a new D.C. branch office at 4910 Massachusetts Ave. NW ... Vanguard Management Associates Inc., specializing in the management of community associations and condominiums, has opened for business in Germantown.

PERSONNEL FILE ... James A. Fetgatter, formerly executive vice president for Savage/Fogarty Cos. Inc., has joined Spaulding & Slye's Washington regional office as vice president for development ... Oliver Carr Co. has appointed Thomas K. Bourke, formerly a project manager at the firm, vice president of D.C. development.