IN GEORGETOWN, where a vacant lot is as rare as a parking space, it's a fair question to ask, "What was your house?"

Rene Carpenter's and Lester Shor's house was a meat market. Mimi and Henry Lavine's house had been divided into three apartments. All were messes when their present owners bought them.

All have been recycled into handsome one-family houses that pay tribute to their pasts. These two houses (and 10 more) will be open to the public during the Georgetown House Tour in two weeks so house buffs can see just how the conversions were made. The Lavine house and the Carpenter-/Shor house both have been finished within the year, which is a good indication remodeling is still a major Georgetown occupation.

Carpenter, a television personality who's now an interior designer, figures she's lived in 38 houses. "And if I couldn't make them habitable in 24 hours, I would think I'd slipped . . ."

Not much more than a year ago, Carpenter was living in a big, rather non-descript apartment building where she was having the walls painted a highgloss Buttercup Gold. Her painter, Lloyd Wright, "a friend who delivers advice and philosophy even as he applies new life to walls," clucked disapprovingly. "This looks awful . . . Why do you stay in this phony, expensive place?"

He went on to tell her about a builder he works for who had bought Thompson's Market, an old Georgetown store said to be the first meat market in the town but abandoned for 20 years. Carpenter and painter went straight over in his pickup truck and took a tour. The downstairs was dominated by "the most incredible walk-in icebox I'd ever seen," she said. The solid oak box, painted gray, is 10 1/2 feet high with carved moldings, glass doors and beveled windows. But even the icebox wasn't enough to make up for the condition of the rest of the house, which, though structurally sound, was deplorable.

"The floor was deep dirt, the walls were filthy. No wiring or plumbing. Rickety stairs. It was a mess." Carpenter threw her hands up and left.

Not long afterward she had a telephone call from Shor - who heard of her visit and suspected she was from the citizen's association or the preservation society or somebody else bent on keeping him from remodeling and living in the building. According to Carpenter, he said: "Lady, please don't bother me. I'm not tearing it down. I'm not building a high rise, an apartment building or a parking lot. Just a simple, two-room pad with a waterfall and a pond inside the front door where I can live in peace with my frogs."

What could she do? Well, of course, that evening she went to dinner with him and they decided to marry - and remodel the house. Meanwhile, during their courtship, Carpenter says they went to the Tile Gallery in Arlington instead of the movies. They married about the same time one of her two daughters (by her former husband, astronaut Scott Carpenter) married. (She has two sons by Carpenter as well; Shor has two daughters. All the children are grown.)

The work began last April with plans by Terry Horowitz. The original plans, Carpenter says, were "spectacular." But nowhere in them was the ice box to be seen.

Love will, as they say, find a way.The icebox was unbolted from the wall by four men, and Dennis Jones spent four weeks removed the paint. It tooks six to put it back on the wall. The icebox became the central feature of the downstairs, with banks of kitchen cabinets made of oak to match at the end of the one great downstairs room. The first floor is divided only by the furniture (her oriental cabinets, his sofa). A two-side open fireplace gives a cozy corner. Plants in the two handsome bay windows substitute for curtains. A funny bath, with a quilt on the wall and an old-fashioned gravity flow water closet, is tucked under the stairs. The staircase serves as a gallery for their modern art collection.

Upstairs is an immense bath, divided into his, hers and their accessories; two closets for the water closets, two sets of wash basins and an immense tub built for two. The rest of the second floor is the big bedroom with an antique drawing board at one end and masses of closets built in with mirrored doors.

Shor, for any woman who liked houses, was a prize. He not only had the house, but as a builder for 20-odd years, he had a crew. One of his great stars is Harold Messenger, a master brick mason, who laid a fireplace and dining wall with the difficult grapevine bond, working alone on a Sunday.

Of course, it didn't all go smoothly. The kitchen cabinets arrived in a huge semi-trailer truck from Rutt's in Pennsylvania a day early, so everything had to stop while it was all unloaded. The bad winter had put back everybody's work, so it took four weeks to get the folding mirror doors for the multitudous closets upstairs.

Carpenter and Shor picked out the bath of their dreams - that fancy round two people-sized Italian soaking tub with the acrylic shower on top (II Bagno series from Thomas Somerville). But when it finally was found, it came in several boxes and the instructions for assembly were in Italian.

But it was finally assembled, and the newlyweds watched the whole Redskin season with a bottle of wine and a television set at a convenient viewing distance from the tub.

Mimi Lavine is a decorator who doesn't mind, in fact likes, laying her own hands on the work. "It's wonderful to have an idea and make it work out." On their own house, Mimi Lavine was the general contractor. "My husband isn't that interested in remodeling work," she said. Larry Milder, a carpenter who started out as an opera singer, came from Cleveland, the Lavines' former home, to do the finish and cabinetwork.

The Lavines - he's a lawyer - moved to Washington a year or so ago. "We looked at 40 houses before buying this one. My husband thought I was crazy to want it. We moved in, started remodeling, and I began my decorating business, all at once. It was hectic."

The house had been built about 1800 - the deed is for 1797 - but by the time the Lavines bought it it needed most things you could mention. The Lavines hired architect Tom Kerns to design a new south end, replacing the most delapidated section, the rear kitchen and porches. The new Kern design is a two-story-high room with large glass areas facing south, topped with a skylight. Mimi Lavine uses the room, with its French doors onto a deck, as her studio/office. A balcony makes a sitting area on the second level. A wall of glass shelves helps keep the light and airy look. Storage cabinets on either side of a built-in seat hold the decorator swatches and samples.

"I've always wanted a barn," said Mimi Lavine. So in the large living room (made by combining two rooms), she left the big beams she found when they tore away the old plaster and the exposed brick on one wall. The sandstone fireplace are nicely carved. She furnished the room with handsome modern paintings, a boldly graphic rug, comfortable contemporary sofas and a handsome Italian painted secretary. One of her cleverer ideas are the mainland China brooms, used as curtain rods.

The house's most charming original features are the bay windows on the ground, first and second levels. The tall bays face west. On the principal floor, the bays turn the foyer and hall into a bright, pleasant room. On the ground level, the bay serves as an extension of the dining room for really big parties. And on the second floor, the bay is a sunny sitting room.

The ground floor is obviously arranged for people who like to entertain. The kitchen itself is tiny, obviously planned for a cook who doesn't need help. The counter and appliances flow around the cook, so she can stand in one space and do it all. Off the kitchen, convenient for company to the cook, is a pleasant family dining room with a fireplace. The room is lined with wormy chestnut cabinets, all painstaking work by carpenter Milder. A marble slab on sawhorses and Coca-Cola chairs provide for meals.

A step down is the formal dining room with its own fireplace - the original opening was much bigger, as you can see by the brick arch above the mantel. The traditional furniture, including a handsome Italian console, is set off by the beamed and wood ceiling and the thickly carpeted floor.

Upstairs is a master bedroom with a bath with a view on the second floor and bedrooms and bath for the daughters on the third. Mimi Lavine has mounted a brass baby bed section as a headboard in one room. A pair of handsome armoire doors makes a headboard for the guest room. Another pair of armoire doors is superimposed on the closets (all new; the original house had none).

Also on the Georgetown House tour. 1-5:30 p.m. April 15 and 16, is the home of Mr. and Mrs. Hugh Newell Jacobsen. Jacobsen, an architect, designed the remodeling for another house on the tour, that of Mr. and Mrs. Cord Meyer. The rest of the houses are those of Mr. and Mrs. W. Averell Harriman, Mr. and Mrs. Hugh Heco, Mr. and Mrs. William F. Arnold, Fitzhugh Green, Dr. Roy Jones, Mr. and Mrs. Clayton Fritchey and Dr. and Mrs. Richard Graham. The Cosmos Club will also be on the tour as well as another house on Q Street.

Each house is only on tour one day, so people should check with the House Tour staff to be sure the house they want to see is open on on the day they plan to go. Ticket information is available at Georgetown Children's House (the beneficiary) 3240 O St. NW, telephone 338-1796.