PAINTER LIFE BERNSTEIN and her husband, Dr. James E. Bernstein, arrived in Washington three years ago with California ideas about space and light, truckloads of very large sculpture and paintings - and plenty of experience in remodeling houses.

They'd remodeled their own house in La Jolla, Calif., with the help of David Raphael Singer. And they had gone on to build two single-family houses to a design by Singer, who is a former student of Louis Kahn, the great Yale architect. Liff Bernstein had even gone so far as to take a course in cabinetmaking.

The Bernstein spent a week in Washington looking for a house, concentrating on the Kalorama area, currently rivaling Georgetown as a posh address. They made a real find - a huge (three stories and a basement) house with somewhere between 20 and 30 rooms (it's hard to count them) on a 75- by 150-foot lot, which is big enough to make them landed gentry in that area.

"We knew we wanted the house," said Liff Bernstein, "when the 10 students who lived in the house came swooshing out of the cracks to tell us how the roof leaked, and it was falling apart, and so on. It was obvious that they loved it and didn't want it sold. They space and light were just what we wanted.

"Singer went through the house with us and said it was just right. He pointed out that in Washington, people spend most of their time inside, unlike La Jolla. So it was better that most of the lot was under roof."

The house sits well back from the street.It has a pleasant east patio, protected by a wall, and the big west lot is large enough for a pool.

There are four or five guest bedrooms and on the second and third floors. James Bernstein has a big room for a darkroom on the top floor. His wife has a glass-roofed painting studio on the second floor. Both use the huge workshop in the basement. James Bernstein frequently has business meetings in the living room. His company, The Health Corporation, is involved in both computers and health products.

The Bernsteins are serious collectors as well as producers of art. If you visit them today, you see paintings hanging on every wall, sometimes stacked several above and below. Works of art even hang from the ceiling, and sculpture and plants fill most of the floor space.

They give many big parties, often to honor artists. When Christo, the man who built the fence on the West Coast as an art event, had a show here, the Bernsteins gave a party for him - with a film show to overflow crowds in their bedroom. They also gave an after-the-opening party for Joan Danziger, who makes papier-mache people masquerading as animals and whose work in the Bernsteins collect.

So the house is designed as a background for art. Everything is painted white. The floors are finished in a light satin with oriental rugs sprinkled throughout. Track lighting illuminates the artwork.

As you come in the front door, there are portraits of Liff Bernsteins and the children by her mother, the well-known Danish artist Aase Hansen. A large portrait of her inside is by Juan Bidilla. A smaller one on another wall of James Bernstein is also by Hansen. Several of the handsome paintings are by Liff Bernstein.

The reception hall is vast and filled with large-leafed plants. Two arches open into a morning room. Here Liff Bernstein keeps her bills in an ancient secretary from her native Denmark. Again, the walls are lined with paintings. A remarkable brightly painted sculpture, a sort of angel on wheels by Benjamin Serranno, catches the eye.

Still a larger Serranno, one that would fill almost anyone's living room, has the place of honor in the spacious, light-filled bay in the Bernsteins' drawing room. This marvel seems to be devils, angels and some unidentified personages riding on an airplane.

One whole wall of the drawings room is filled with modular bookcases by the Danish designer Mogens Koch. "We had half of these in our California house," said Liff Bernstein. "And we ordered the other half to make a wall here. Only in the 15 years between the price went up tremendously. And it took us a year and a half to get them." The bookcases are filled with art catalogues, some small pieces of art and books.

A fine Gothic fireplace centers another wall, and there are bamboo chairs and a Selig De Sede leather sofa from Switzerland, a Gene Davis painting and a Japanese screen.

The Bernsteins paid $185,000 for the house. It sounds like a lot of money, but the price was not bad by Kalorama's price scale. The house needed much done. The Bernsteins figured it took them 18 months to get it the way they wanted it. Liff Bernstein worked all day long and her husband worked all night long. And they both worked every weekend. Of course, there's more they'd like to do. So far the house isn't airconditioned, but tall ceilings and tree cover help a great deal.

To date, James Bernstein figures they've spent about $55,000 on materials, not counting their own work. At that, he was able to get builders' prices on most materials "by simply asking for the wholesale price. The only place I didn't was at Hechinger's, but their plywood seemed to be as cheap as the wholesaler's anyway. We bought 50 sheets at a time, while it was on sale. Liff got them loaded on our station wagon, five sheets at a time."

The Bernsteins did almost all the work themselves. They did have the roof repaired by a professional. He weatherstripped, realigned and caulked the metal casement windows himself. The windows, with elaborate leading, are one of the glories of the house - diamond patterns area at the top of almost all the windows, back to front, up to down. She plastered and painted. She had to paint the living room and dining room twice because the first roof repair job did not stop the leaks.

He installed eight can spotlights in the ceiling - a difficult and tiresome job "though not as bad as you'd think." It involved finding the joists, cutting circles between them and cutting smaller holes to snake the wiring through. In the hall and living room they used track lighting - "Anyone can install those." He bought all the lighting fixtures, Lightolier, from Atlantic Electric Company.

The biggest job was the kitchen. He did the structural work, but she did all the cabinetry. They tore out all the old walls between the pantry, the kitchen and the servants' dining hall and made, instead, a breakfast room with storage for the children's art equipment; a neat, two-aisle kitchen and the "womb room."

The big kitchen counter facing the dining room serves as a buffet for the parties - which the Bernsteins give at the drop of a paint brush. The counter is surfaced with a handsome pink Italian marble, from Antonio Troiano in Beltsville.

"At the time we bought it," said Liff Bernstein, "marble cost us no more than butcher block or plastic laminate, and we thought it looked much better. People told us all sorts of dreadful things about it marring and staining. But we've had it three years, and we think it looks fine. Once in a while we get a bid of lemon juice on it, and that will look rough and powdery for a while, but it seems to wear off eventually. We've also put hot pots on it all the time, without any harm."

James Bernstein said he supported the marble with an inch and a half of plywood underneath, well-braced. "Most of the trouble with marble comes from insufficient support."

The new "womb room" is the place where everybody sits while the cook performs. The Bernsteins are well into elaborate cookery, so they're worth watching. He built the platform which was then covered (unsatisfactorily) by a carpet company (here nameless) in a brilliant red. The Bernsteins also built a new stoop and installed a new back door.

Upstairs, he took out two closets which cluttered up an otherwise enormous roomwith a fireplace. Now they have a seating group around the fireplace, a large sculpture by Serranno, and new closets which seem to hold more yet take up less room. Liff Bernstein made their king-sized bed.

The children's room was once the library. James Bernstein built a platform, carpeted by his wife, that undulates through one end of the room. The daughters' mattresses, tucked into huge comforters, rest on the platforms. A long built-in cabinet serves as headboard, while hiding the radiator. A wall of shelves holds dolls, records, books, stereo and a mirror. This room is divided by big thick closets opening on either side. The other room is a small sitting room for the girls.

Liff Bernstein's painting studio, once a "solarium," is through the door. It has great deal of glass. The current project is air-conditioning it.

Not so important this summer since the Bernsteins spent August in Maine.

Today, the Bernstein house is a rarity, a house that opens its doors and bares its owners' lives. As soon as you come in, you know right away what the Bernsteins are like and what they like. Obviously, it is not a house where the major decisions or the major work was made by outside professionals. It is a house shaped by people for themselves.