HUGH NEWELL JACOBSEN has, in his words, "laid hands on" eighty Georgetown houses in one way or the other. He has been the architect for small bathrooms and large mansions. In the process he has become the architect who made modern design respectable in Georgetown.

So you might expect Jacobsen's own house to, as that awful architectural cliche goes, "make a statement." Translated that means "shout what it's about." It must be a terrible temptation to an architect to put into his own home all the design tricks and treats that his clients won't let him use in their houses. Some architects do design their own houses this way and they tend to come out looking like the Trend of the Month. Those architects move a lot.

"I might have been tempted into something like that," Jacobsen said the other day, "if I had been designing the house for myself and my family. But I was saved from all that because the house was actually designed as a rental property for some mythical Republican with 3.2 children moving into town.

"Houses, you know, have to survive everything, from measles and chickenpox to changes in popular taste. This was the squarest house I ever designed. And so it doesn't date as 1970 or anything.

"If I had designed it for me, I would've had to make a statement , but then I would have had to live with its rude remarks. This house gave me such freedom and relaxation, because I didn't design it for me."

The front part of the house was built about 1803 as a Federal two-story red brick with two dormers. In 1940 a "tasteful bay window, a third floor and Italianate brackets" were added, Jacobsen said. The house also had that rarest of Georgetown advantages; a side yard, bringing the total width to thirty-three feet for house and yard. Two speculative builders had even tried to get zoing to squeeze in another house.

Jacobsen had another plan, one of his methods for insinuating modern amenities behind proper Georgetown facades. The result is worth a close look for its answers to common Washington add-on problems. He tore down and carted off all the old rotten wings in the back, leaving only the three-story high front. A brick wall stretching across the building line at the side suggested a walled garden.

So Jacobsen made a formal entry court at the side, and built what amounted to a whole new house behind. The old brick wall and the ivy-covered slope and bluestone steps almost conceal the new section from the street, leaving the street scene intact. The new wing's roof is a mansard to minimize the height. The light over the gate and the street number over the entry garden gate are designed to distract your attention from the original door, to the right of the old house. The old part of the house sits right at the sidewalk.

The old front door has become officially the "back door." Though it serves the kitchen through the old entry hall, it's primarily the children's entrance.

That old stair is the only link to the 19-year-old son's third-floor bedroom. Jacobsen enjoys the way the detailing on the stair changes from the second to the third floor since the third was added so much later.

The formal entrance to the house, through the entry court and into the new section, leads into a skylighted hall paved with bluestone. Visitors pass by the kitchen, a narrow affair where Robin Jacobsen, famous for her food, performs now-you-see-it-now-you-don't tricks. People are always amazed at the quantity and quality of the food which comes out of a kitchen where you might expect to have to put away the lettuce before you get out the tomatoes.

The hall is that rarity, a true center hall, surrounded on four sides so that all rooms become, in effect, dead-end rooms, except for a passage to the patio, which actually seems an extension of the living room. Yet because each room has two doors, there isn't the feeling of being trapped, even when there's a crowd.

The dining room, the only public room which belongs to the old house, has had certain subtractions to make it work with the new addition. Jacobsen, as he usually does in such remodelings, removed all the moldings for a cleaner line. (Jacobsen was asked, when he served as consultant on the restoration of the Arts and Industries Building and the Renwick Gallery of the Smithsonian, if he was putting back in those buildings all the moldings he'd removed from those eighty Georgetown Houses.)

The two-over-two paned windows were brought down to the floor - another Jacobsen rule. "It does a great thing with the light." To give some feeling of privacy from the street, the windows were fitted and shutters. "I hate drapery, though I suppose people who have drapery aren't actually evil."

The dining room can be entered from the original front hall, which also connects with the kitchen, a handy feature when the dinner party rates a maid. Its other entry is into the center hall.

You step down into the ten-foot high eighteen-by-twenty-four-foot living room. The first thing you notice is the patio. The ten-foot high glass doors, and a bay echoing the old bay at front, lead the eye outside. The bluestone deck is level with the dark-stained oak floor of the living room (if he'd know it was for himself, the living room would have had bluestone too, as does the entry foyer and halL, Jacobsen said).

At one end is a fireplace, but the sofa, chairs and ottomans, in typical Jacobsen fashion, ignore the fire to group tightly in the middle of the room.

By keeping the furniture in the middle, the empty space flows all around them, lapping at the glass and the fireplace.

At one end of the room is a doorway, with sliding pocket doors which appear and disappear in the Victorian magic manner, leading to the library. The wall-to-wall books are almost like a color collage wall.

Everything is arranged with great eye to the straight line. On the library desk, the new catalog from the 1925 Art Moderne show in Paris is arranged exactly atop a new architectural book, to made a proper geometric design with the telephone.

This classical, ordered quality is a major factor in the success of Jacobsen's Georgetown remodeling, his own included. Though stripped down, clean-lined and clear-thinking, it has such a disciplined, high-minded, no-hair-out-of-place manner that it does not threaten the most conservative traditionalist. On the other hand, those of us of the romantic (cluttered or magpie) school tend to feel, after lunch at the Jacobsens', that we ought really to go home and have a garage sale.

As usual, the windows in the library are floor-to-ceiling, in this rather narrow (nine feet) but long (eighteen feet) room. There is a built-in liquor cabinet and an adjacent powder room.

Jacobsen thinks that one of the most important elements of this end of the house is the wall, painted gray, which encloses the patio and its holly trees (columnar American).

"I wasn't used to light, except that which I let in myself through windows and skylights. The wall, which already existed, surprised me by reflecting in so much sparkling light. That wall has taught me a great deal. Though I think if it had been white, it would have been too glaring," Jacobsen explained.

The upstairs shares that light. The master bedroom again has floor-to-ceiling glass walls, and a six-by-eight-foot mirror set so it too reflects light. The sheets and bedspreads are also gray, in a Marimekko fabric, against a beige carpeting.

On this floor are two more bedrooms for the younger boys. The oldest, by rights, gets the third floor, in lonely grandeur, because the new wing is only two stories high. Each of the four bedrooms has its own bath. "I probably would have found something else to do with the $2800 each extra bath costs, if I'd designed the house for me," says Jacobsen.

Jacobsen is fond of pointing out to his clients that "if you make the driveway longer you'll have to make the living room shorter." And indeed, if he'd had his druthers, the money saved through cutting back on the number of new bathrooms would probably have gone to make one side of the hall roof glass.

"We and the people we know," says Jacobsen, "all tend to put our money into our house. We don't have yachts or expensive cars, that sort of thing.

"What's important is the house, where you live. Architecture is space that should make us look and feel better. It's the architecture that's important, not the furniture. The furniture is a slow third after the architecutre and the art on the walls. No one is married to the sofa."