For Ellen Ashton it was a matter of convenience. When she saw a self-employed home contractor working on another house in her Fort Dupont neighborhood in Southeast, she asked him to do some carpentry work on her two-story home.

She gave him a $400 down payment to install a solid oak door. Today, a year later, the door is in place but still has streaks of shellac hastily applied and has yet to be finished properly, Ashton recalled last week.

"I asked him to come back, but he didn't respond," she said. "It's not even solid oak as previously stated to me."

Local consumer agencies say Ellen Ashton is among scores of Washington area residents who have been swindled out of their money as each spring unwitting homeowners fall prey to unethical, unlicensed home improvement contractors.

Consumer and legal experts say the most unethical among the contractors typically scour neighborhoods soliciting work as the weather warms, guaranteeing at bargain rates work that often falls short of their promises. Charges against them range from simply performing shoddy work to engaging in criminal fraud.

In many cases, residents such as Ashton have lost money to contractors who began but never finished jobs and were difficult or impossible to find afterward.

In the worst scenario, some residents have lost thousands of dollars to repairmen who were given huge advance payments in order to purchase materials but never returned to begin the work.

"He's doing his business out of his hat. He doesn't have a fixed location, a fixed address, and you can't put your hands on him," explains Matthew Green of the District's Department of Consumer and Regulatory Affairs. "That's the real problem."

The problem is regionwide, according to the Better Business Bureau, which last year received more than 750 written complaints. More than 500 residents filed complaints with the District's consumer agency.

According to Green, the problem is found "wherever there are homes in a state of disrepair and they're individually owned."

In financial terms, the problem is perhaps more serious than mail order and auto repair, which also rank among the top consumer complaints. "If you were ranking by how much money was spent, it would be number one," according to Donna Crocker of the Prince George's County Consumer Protection Commission.

Despite the number of victims, consumer experts say problems with itinerant contractors can be avoided. City and state governments require small contractors to be licensed, requiring that they have proper insurance and post a surety bond. Small contractors should be able to show their license to a potential customer, according to government officials.

"That's the biggest protection a consumer has," said Arlington County consumer specialist Donna Veno.

Most itinerant contractors are unlicensed, according to experts. In the worst cases, they give their customers business cards that are later determined to have fictitious phone numbers and addresses.

"Consumers don't do enough checking before they give someone seven, eight or nine thousand dollars," said Green of the D.C. consumer department.

One of the main reasons is the on-the-spot, high-pressure sales pitches itinerant contractors use.

Unethical and incompetent contractors are among a variety of specialists who are involved in such fields as asphalt paving, roofing, auto body work and general home repairs.

Consumer specialists say some of the contractors target certain communities, depending on the age and condition of homes and the age of residents and their own location.

District consumer and building authorities say they have many complaints about shoddy roof repairs by itinerant workers, apparently a nationwide problem because of the very nature of the job, experts say.

"The consumer is not going to get up there and check the roof out," explains Fred Goldberg, a Washington attorney who specializes in consumer problems.

This spring, Maryland has begun alerting residents about unlicensed furnace cleaners operating in the area.

Ashton filed a complaint with the Consumer and Regulatory Affairs Department. An administrative judge last month declared that she is entitled to a full refund. She has received only partial payment.

"This was my first experience" with an unlicensed contractor, said Ashton. "I guarantee it will be my last."