Home-building is a family affair for Donald Minehart, his wife Bette, two sons Glen and Curtis and Glen's wife Krista: The family is about to complete a contemporary house on Walker Lake Road in Great Falls. a

The house is one of scores of large new homes now being built in the wooded area on both sides of Walker Road, about three miles east of the Great Falls crossroads where two small shopping center recently have been developed. f

The house built by the Mineharts, already under contract to a buyer for $425,000, is set on a two-acre wooded lot with its own well and septic tank.

"We do everything but the drywalling, heating, plumbing and electrical work," said Donald Minehart.

Slated to become the main residence for a high-income family with four children, the shake-roofed house with redwood exterior siding and some stone trim also has about 5,500 square feet of living space.

A ceramic-tiled foyer leads to a step-down living room with a raised-hearth fireplace. In the family room, which also has a large south-facing window area, a partially tiled floor will catch winter sunlight to produce extra heat. a

A redwood deck in back connects the living, dining and family rooms, which look out over a wooded area. The first-floor master bedroom has a walk-in closet with a skylight and a lot for addition storage; the adjoining bathroom has a whirlpool tub. The kitchen houses a laundry area.

Floors, rails and stairways throughout the house are oak. An oak stairway leads to a carpeted walkway that connects two sections of the second level. On one side is a library-den-studio room with a fireplace and an oak-treaded circular stairway leading to the master bedroom below. The other side of the second level has two bedrooms with a connecting bathroom. One of the bedrooms has a loft reached by ladder.

The first Minehart joint venture was completed some time ago: Soon after their marriage, Donald and Betty Minehart built their own home in Hecla, S.D.

"Just as Don and I did years earlier, Glen and Krista built their own first house," Bette Minehart said.

The elder Mineharts, who spent 20 years in Asia where Donald Minehart worked for the Agency for International Development, the University of Illinois and the Ford Foundation, returned a few years ago to the United States and bought a house in Sterling.

"We then redid it to our taste and decided to build homes," Bette Minehart said. The couple had saved some money and borrowed additional funds to buy a lot. In 1980, using as the builder the small firm run by son Glen, 30, the Mineharts built, completed and sold their first house in Great Falls.

The Mineharts are so satisfied with their workmanship on the house at 10114 Walker Lake Dr. that they will show it to anyone who comes by on a Sunday afternoon.

"It's been sold, but we are really proud of what we have done," Bette Minehart said. "We don't make much money, [an estimated $40,000 on a $425,000 house], but we like what we do."

"Don works on the house every day except when he's out of the country on a consulting assignment," she added.

Daughter-in-law Krista contributes to the design of the houses. Son Curtis, 27, also works as a carpenter for Glen's construction firm. Two other Minehart children do other things. David, 33, is a photographer in San Francisco. Nancy, 26, is a hair stylist in Great Falls.