Michael and Terry Marks, who are buying a house in the Woodstream subdivision off Good Luck Road in Greenbelt, joined 30 other prospective owners in that community on a recent Saturday for an educational walk through one of the town houses.

It was conducted by John Dodds, vice president of construction for Northbridge Limited Partnership, the company building the town houses for developer Michael T. Rose.

The Markses, who live in an apartment, said they really don't know much about construction. Michael said they were "stretching to make the purchase on our two incomes because we want to have our own home."

The buyers donned hard hats and followed Dodds around the unfinished house to learn about the basics of construction. They had been invited there as part of a customer service program begun a year ago that has helped "save a lot of misunderstanding" between buyer and builder, Rose said. The program is open to anyone interested in home construction, a spokesman said.

Dodds answered questions about drainage and supplied details about the foundations and walls in the $80,000s-and-up houses. He explained how the blanket insulation would be placed between the wall studs.

He also showed the group how the stairways's jog landing would permit owners to move a sofa to the living room on the second level.

Dodds described the attic and roof construction, adding that some unfloored crawl space might be available for minor storage. He pointed to the spot where a skylight would be fitted into the roof.

The buyers, who hope to move in by spring, were told that construction is about a week behind schedule because of street resurfacing to enable trucks and vans to move around readily during the cold months. "We should make up that time because of easier access," Dodds told them.

Developer Rose says that most buyers in the subdivision attend at least two of the educational sessions, "and some of them even bring friends."

The town houses in Woodstream, in a grouping called Carriage Walk, are being built by Rose in conjunction with the National Housing Partnership, which provides equity capital to builders of homes for moderate-income buyers.