A D.C. Superior Court, grand jury yesterday charged a Virginia couple and their son with conspiracy to defraud customers of their roof-repair and waterproofing business.

In an 11-count indictment, the grand jury alleged that as part of the conspiracy, Cecil C. Nichols, 50, Ann M. Nichols, 41, and Michael P. Nichols, 20, told customers in the District that work had been completed on their homes and buildings when they knew the work was superficial, incomplete, or not done at all.

The defendants also claimed that their work was guaranteed for a number of years and that further repairs would be completed for free when they "had no intention of fulfilling such guarantees," the indictment said.

In addition to conspiracy, the defendants were charged with making false representations, grand larceny and fraudulently taking money for their own use when it was intended to pay for roof repairs.

The Nicholses live at 7103 Evanston Rd., in Springfield.

According to the indictment, the defendants operated their business under various names, including Nichols Painting and Roofing Company, Nichols Roofing Company, Duke Roofing Company, A-2 Roofing Company and Vicks Roofing.

The defendants solicited roof repair and maintenance jobs by advertising in newspapers, the indictment said. The conspiracy took place between jan. 1, 1975, and last April, the grand jury alleged.

The indictment described eight incidents, involving about $2,000 in which the defendants were paid on the basis of their allegedly false representations about their work and guarantees.