‘You just feel like you stepped into a painting.’

In the field of interior design, the San Fernando Valley, with its proliferation of apartments and tract houses, may long have been regarded as a poor relative of the older, moneyed communities such as Hancock Park and Pasadena.

That is changing at last.

The Valley has been quietly attracting interior designers, and about two years ago they formed the Valley’s own chapter of the International Society of Interior Designers.

This spring, to show its stuff, the young group has created the Valley’s first design house, much like the annual benefit for the Junior Philharmonic in Pasadena.

A design house, briefly, is an old and possibly derelict mansion that has been completely redecorated for public display by a team of designers, each assigned to a different room.

All the work and materials are donated, and an entry fee paid by each visitor goes to a charity, in this case the American Cancer Society.

The Valley design house, called “White Oaks,” is a 50-year-old colonial on an acre at 16930 Magnolia Blvd. in Encino. It’s unmistakable. An oak stands in the middle of the road out front.

The house belongs to comedian Tim Conway, but has been vacant for several months.

Work on the face lift began in January and is nearly done.

The public showing will begin Sunday and will continue through April 27. The house is open from 10 a.m. to 9 p.m. Wednesdays and Fridays, and from 10 a.m. to 5 p.m. Thursdays, Saturdays and Sundays. Tickets are $10 and may be purchased at the Cancer Society office, 14602 Victory Blvd. in Van Nuys.

I stopped by the house Friday, a week before its opening. Construction was still much in evidence. Several designers stopped what they were doing to lead me around and describe their work.

Many small rooms have been expanded, creating a stunning expanse in key rooms, such as the kitchen, without sacrificing such amenities as the nanny’s bedroom and butler’s pantry.

The color palette prescribed for the designers consisted of mauve, French blue, ivory and pastel green.

Most of them used the mauve and green in bold combinations that occasionally suggested flavors of ice cream.

The hand-painted wallpaper in the entryway, for example, had a pattern of mauve swirls over white. It could have been raspberry swirl, although the designers called it faux marble, a term employing the French word for false.

There was a good deal of faux marble throughout the house, including the baseboards and ceiling molding in the living room and dining room. These were painted a mottled green and were lined with gull feathers to simulate cracks in the marble.

“We are very proud of this faux ,” said Karel Lambell, who designed the dining room.

Lambell was awaiting the arrival of a specially-made vitrine (that’s an armoire without a door) that was to fit into a small closet under a stairway with a faux marble border.

Up a cherry mauve staircase there were several notable rooms, including a women’s retreat, with a boysenberry carpet.

Designers Suzy Martin Judis and Marilyn Perlmutter called it M’Lady’s Sitting Room. They lifted up a piece of plastic sheeting to reveal its piece d’resistance --a wall cleverly painted to look like a frame window overlooking a scene of roses, daisies and wild hares.

It was a style called trompe l’oeil , French for “fool the eye,” they said.

“You just feel like you stepped into a painting,” Judis said. “Everything is very impressionistic.”

The master bedroom, on the other side of the hall, had a side chamber in which a sauna was being installed and, next to that, a private bathroom with a bidet. That’s a French appliance. If you have to ask what it is for, you probably don’t need one.

At the top of the stairs was the gentlemen’s retreat. It had been converted from a bedroom and was conceived as a place for the man of the house to congregate with his guests while the women were in M’Lady’s Sitting Room.

Its designer was away, but Jane Brooks, who was in charge of the bathroom next door, spoke highly of his work.

“Actually, his room is the room I like best besides my own,” she said.

Without a trace of faux humility, Brooks confided that her bathroom was the most expensive in the house.

“There’s $65,000 in this bathroom,” she said.

Its walls were covered with hand-painted paper from Boca Raton and deep green paneling from Royal Splash in England.

“This is Royal Splash’s most expensive finish,” Brooks said.

It had traces of gold leaf on a deep green background covered by 14 layers of lacquer and a poly resin finish.

On the floors were marble and a mauve carpet inlaid with a large floral design repeating the theme of the hand-painted canvas upholstery on the ceiling. The canvas was drawn into ruffles, called shirring, that radiated toward the Royal Splash tub.

“I wanted it to radiate to the tub because that is the most expensive area.” Brooks said.

The tub, without the 24 carat gold-plated fixtures, cost $14,000, she said.

“This is what they’re calling the jewel of the house,” she bragged.

Eschewing both the colonial theme and the French nomenclature of the rest of the house, Brooks identified her bathroom as opulent elegant.

In the WC, everything is just as it seems.