SOMEBODY ONCE told me that you need to have a very good marriage before you start to remodel a house together," said Sharon Callahan, as she enjoyed the unaccustomed leisure of being between remodeling projects.

"My husband is my best friend, so I didn't find the remodeling hard on us at all. As a matter of fact, it was rather nice to have a project together. On the other hand, now that most of it is done, Jim says often that he would never ever do it again. I don't feel quite that way about it. Though the summer I spent putting up all that wallboard was boring."

The Callahans have a splendid 1908 frame house in the middle of about a half-acre in McLean. The location is great, just across the street from the school their 11-year-old daughter Kendra attends. Best of all, the quaint gray house with its trim blue shutters isn't duplicated by the other houses up and down the nearby streets.

They bought the house six years ago, when they returned from the Marshall Islands, where Callahan worked as a systems analyst. Working most nights and every weekend, they have transformed the farmhouse into a pleasant house where contemporary luxuries such as space and light harmonize with antique luxuries such as fancy trim and a feeling of nostalgia.

They pitched in to paint everything, redo the floors, put up wallboard, build closest and install laundry machines in the old pantry and a powder room under the stairs. It was a lot of work.

Then one day, when everybody was really tired, they realized the house still lacked the space and pizazz they wanted. So they called Richard Ridley, a Washington architect who doesn't mind small jobs. They liked his first plans fine, but preferred the second ones. From the beginning, they explained what they wanted was a design they could complete themselves.

They decided on two major additions: a two-story-high breakfast room and an inglenook, or hearthroom, and a bay in the living room. Both additions were rather like elastic; they added the "give" the house needed. By the time it was all finished, the Callahans figure it cost somewhere between $18,000 and $20,000, not to mention the priceless value of their own work.

First the Callahans hired a general contractor who put up the basic shell of both rooms. Then Jim Callahan installed the wallboard. "I took over then," said Sharon Callahan. "After I'd watched him do the work upstairs I decided I was better at taping and finishing the joints on the wallboard. Not to be sexist, but I think women have more patience for that sort of exacting work."

The breakfast room has sliding glass doors onto a deck, with a planter that serves to keep people from falling off. The ceiling soars to 17 feet, making the upstairs hall into a balcony with a large rectangular cutout to peer through. Several high windows in the breakfast room also light the upstairs hall. A heat return at the very top helps contain all that heat.

On the wall is a story picture, actually a sort of bamboo road map, from the Marshall Islands. The table is Callahan handwork: The metal frame had lost its glass so an oval of wood from the Door Store replaced it.

In the living room, the Callahams added another two-story-high addition. (Actually its the other end of the breakfast room, but with a wall between.) The two-story part is not that much, almost just a narrow light well, because a section that eventually will be added to the daughter's room cantilevers into the new alcove. Mainly, the addition was intended to add a fireplace. On either side of the hearth is a banquette, with lots of cushions. The floor is of very practical fire-safe quarry tile. Sharon Callahan did all the grouting - "it was really fun" - after her husband had laid the tile.

On the west wall is a pleasant bay, big enough for the sofa. It is certainly in keeping with the style of the house since the bay at the end of the dining room is original. Bays have the great advantage of thrusting you into the garden and bringing in the light from three sides.

All the windows in the house are protected by interior shutters, sometimes top and bottom, sometimes just at the bottom. "I like the looks of the shutters a lot," said Sharon Callahan. "Jim installed them and I painted them. I certainly did get tired of that. We had to have shutters because of our two cats, Pepper and Tabitha. They shred curtains."

Callahan took up the boards of the old front porch and replaced it with a red brick patio, held in place by a railroad tie. The effect suits a farmhouse of its period and is a practical way to clean your feet before you come inside.

In the good advice category, Sharon Callahan says she wishes they'd begun with an architect, because some of their early work had to be torn out for the additions. "And my husband says over the over again that he would do all the work next time before moving in. But our plumber, Buddy Putnam, and the electrican, Jim Dent, were great about doing things quickly and working out ways to give us at least some water and light while they were working on other projects.

"I suppose the best advice is when it comes to that point that all you can do is laugh or cry, it's better to laugh."

Now the work is finished, Sharon Callahan says she feels as though she has vast amounts of spare time. But then there are the French doors to be installed in Kendra's room so she can go onto the balcony (the top of the living room bay) and the wall to be torn down to extend her room. But for a while, thank you, the Callahans are resting.