THE HOUSE of Anita and Sheldon Shalit was almost completely gutted when they bought it for $60,000 two or three years ago. (Shalit is a health program administrator with the National Institute of Mental Health. Anita Shalit is a program analyst with the Administration on Aging). Contractor Ken Wilkinson, who now has formed an association with Fong and architect Henry Grant Ingersoll, rebuilt it to Fong's plans for about $135,000. The result is about 3,000 square feet of livable space.

From the street, the house today is little changed. But inside, floors have been raised and lowered, ceiling heights varied, and most of all, in the middle, a stairway to the sun.

The dining room is up a few steps on the north of the narrow hall (less than three feet, but the Shalits are thin). The kitchen is also up a step or two. The kitchen has a pass through just about the counter to the hall, a marble counter for rolling out pasta, and a counter on wheels that moves to the oven side or the cleanup center.

The hall ends in the middle of the house. Steps go down to the pleasant living room, with its great fixed glass walls on either side of the fireplace. The big white-painted side walls serve as gallery for the Shalit's art collection. The big blue velvet modular seating looks as though it were made for the room, but it's let over from their previous house. All the walls in the house are white, giving it a scrubbed, contemporary look.

The great glory of the house is the stair, rising in the middle, between kitchen and living room and going up three flights to a 4 by 4-foot skylight.More light comes in through the 12-foot-wide sliding glass doors leading to the third-floor roof deck. The stair has a metal ship's rail on the second and third floors. Lightdesign by Ingersoil. On the first floor looking up the effect is no nautical that you'll hear the sound of the ocan liner casting off.

"When we have parties," said Sheldon Shalit, "people don't ask, they just feel free to wander all over the house. The steps are a favorite place for people to sit. There are always a few up on the third floor, in the sitting room that's the room in the middle. And some londer is usually reading a book by himself in the library. Even at night , they spread out on the third floor deck, sitting on the built-in bench/lockers.

Anita Shalit noted, "You can yell down from any part of the house. But when we first moved in, sounds seemed to deceptive. It took us a long time to figure where the shouts were coming from."

The Shalit's master bedroom is on the second floor and so is Alexandra's, their 2 year-old daughter. Each has its own, completely tiled bath. The adult bath has a tiled bench so you can have your shower sitting down. A third bath adjoins the library on the third floor, in case of a guest.

To make the pleasant rental apartment on the lower floor, the Shalits dug down to make possible sliding glass doors onto a patio. "It was expensive," said contractor Wilkinson, "because of the water main, it took quite a bit ot talking to keep the city from making us put in a whole new main, north and south." The apartment has a living room, a neat bar kitchen with a pass through, and a small bedroom with another all-tile bath. Underneath the living room is a workshop/storage area.

Wilkinson put in 9 1/2 inches of fiberglass insulation in the ceiling, 4 in the exterior walls, and 6 between the basement and the first floor, to cushion against sound. "The tenant says he never hears us," said Shalit. The tenant apartment is heated and cooled by a heat pump. The Shalit's part has an electric air conditioner and a gas furnace, all mounted on the roof, installed by Garrison Heating and Cooling Co. So far, the worst air conditioning bill they've had was $65. Most of the windows are fixed glass, with just enough openable sash, including the deck doors, to make an airsweep up the staircase.

The Shalit and the Frings houses, though far from cheap, show that it is still possible even in this market to have a custom-designed house at about what they would have had to pay for similar housing, not tailored to their tastes.