WALKING ALONG one of those nice old downtown streets where every house in the row is worth a second and a third glance, you can see right away that there's something different about this house. The window grilles are sunbursts, and the shutters in the living room bay are filled with strips of colored fabric carefully sewn together.

When Maria da Conceicao met us at the door, we could see that Sao -- as she likes to be called -- is like a spider, spinning a home for herself with fine threads.

Everything -- shutters, sofa, wall hangings, upholstery, table covers -- is sewn by Sao's fine Portugese hands. Much of the work is in fabric collages, fabric cut in small pieces and patched together with delicate stitches, as though she had used fabric as yarn to weave a new cloth.

That day, Sao had on a long velvet printed skirt and a vest made of bits and pieces of laces, embroidery and strips of fabric. She wears a small doll as a necklace. Combined with her immense dark eyes and flowing hair -- and small, delicate stature -- the effect is startling. "When I wear the doll necklace, I am not shy, because I know people look at it instead of me," she said. Looking at the doll, I began to be just a bit frightened, especially when I noticed her black cat, who follows her around like a familiar.

Sao is 33, but she looks about 12. She speaks with a soft voice as smooth as syllabub.

Many people know the intricately sewn clothes she makes. She sells every piece she finishes, and people have to wait for costumes. A show of her work, called "Wearable Art," opens Thursday at the Textile Museum. Other pieces by her are on sale at the Renwick Gallery shop. She shows her art tomorrow at the Women's Democratic Club luncheon, and a book about her pieces, written by Nancy Grubb of the Hirshhorn Museum, will be published this month by Viking Studio Books -- with a Penguin paperback on the way.

Her clients have included television personality Nancy Dickerson. A chasuble she made for the National Cathedral was shown in the Vatican Museum's exhibit of religious arts and crafts.

Sao's husband, Patrick Heininger, a lawyer, is handy with a hammer. He's the helpmate who makes the frames for her fancies. The shutters, for instance, are heavy-duty artist canvas stretchers, which he used to frame her fabrics as a substitute for curtains. The sofa and two chairs in the living room have wooden frames by Heininger, cushions by Sao. The large snake, 40 feet long, hopes you'll think he's a chair. The snake is made of knit fabric sewn together by Sao and coiled to make the seat. She has sold 12 of these at $400 for patchwork and $780 for knit. It takes 50 bags of polyester to fill one.

Also in the living room, on a bust, is Sao's latest, a jacket put together of shiny pieces of fabric cut like coins, with a matching helmet.

The dining room, past Joan Danzinger's winged papier-mache creature, has one of Sao's strip hangings on the wall, and a tablecloth made of patchwork. In the middle of the table is a centerpiece made of a doll bed with a funny, bald doll dressed in an elaborate costume. "Whenever we have guests, I like to make something interesting for the center," Sao said. The doll was surrounded with fruits and vegetables, so it looked as though she were serving them.

The dining chairs are an assortment of old Victorian patterns. The kitchen, open to the dining room, is Heininger's tour de force. He laid the large square Mexican tiles, built the handsome stepped cabinet and the frame from which hang the pots and pans, Portuguese style.

The music room is adjacent. Here in brillant red grandeur sits the harpsichord Sao and Heininger made together. He is a serious musican, usually playing the recorder. The walls here are paneled halfway up.

"We were going to scrape the old paint off ourselves. But then we gave up and had someone else to do it. They thought it would not be a hard job, but it took them two weeks." The old Victorian sofa is another Sao upholstery job. The basket lantern makes a Sao-like pattern on the ceiling.

The second floor is all Sao's. Their architect, Daniel Kelleher, who specializes, Sao said, in studios, took out all the interior walls to make one huge workroom. They paid $100,000 for the house and have spent another $25,000 to put in a basement apartment.

Sao's dress dummies, gowned in her latest work, stood as if waiting to receive us. Here is the bride, a marvel of lace, flounces and flourishes, with Juliet cap to match. The ensemble already has been worn; but its owner, Eliza Rathbone of the National Gallery, lent it back to Sao for the show.

Another dummy, the widow perhaps, wearing a black cape and heavily veiled hat, lurks at the foot of the steps going upstairs.

Some of the costumes are displayed on flat figures, designed for Sao by Peter Danko. Danko's innovative plywood chair -- Sao thinks it's the very first one he made -- is downstairs, with a Sao seat, of course.

Three big work tables and a fine desk with pigeonholes were made for Sao by her husband. "I draw everything first," she said, and showed us her sketches, themselves worthy of display. "I make my own patterns after the sketch. I use new cloth even though I cut it into small pieces like scraps.

"I buy cloth at the G Street Remnant Shop because the owner, Judah Greenzaid, will order a whole roll for me, even though I need just a yard of some particular color. I do use antique lace and embroidery," she said. She has only a small, cranky-looking, doll-sized sewing machine. "I do everything by hand," she said.

Dolls from a recent show hang from the ceiling of the studio. All have wings, but they look more as though they had flown up from the nether regions rather than down. One wears a pair of real bird wings, with the head forming a hood for the doll. Another has a ruff of feathers. A cabaret doll kicks up her heels from a cascade of lace ruffles.

The bathroom on this floor is less mysterious than the room. "I hated the tile," said Sao. "So I took all the scrap wood my husband had left over, and pasted them on the tile with panel adhesive."

Sao learned to sew as a little girl, going to the convent school across from her home in Evora, a Portuguese town noted for its museum. The sewing lessons have stayed with her longer than the Catholicism, but "I am very grateful to the nuns for their patient instruction in embroidery and fine handwork."

At 18 she married a Danish lawyer and went to live in Denmark. She became a part of the Danish handcraft guild and was welcomed for her knowledge of fabric techniques. She studied costume design and fine art there and "I learned how to turn watercolor paintings into fabric works," she said. About 13 years ago she began making her collage wall-hangings. The clothes came three years later. "I began making clothes to make money faster," she admitted. "Now I sell enough to support my art and my self."

She lived for a time in Kenya with her previous husband, and then that marriage broke up. She met her present husband in Kenya, and came to the United States to visit him. They married, and she's been here ever since. She keeps her Danish citzenship but thinks occasionally about resuming her Portugese citizenship, though she admits she speaks more Danish today than Portuguese.

Sao said Heininger "admires and understands what I do. Every night, when he comes home, he says, 'I want to see what you made today.'"

She goes to work in the morning as soon as he leaves the house and works through the day. "It's not discipline, it's drive," she said. "I am happiest here in my studio."