It's not ooh-and-aah architecture, but it is quite fine: a brand-new office building at 1818 N St. NW that takes its place comfortably on the southern edge of the Dupont Circle historic district, something that definitively cannot be said for the lackadaisical buildings that have been creeping northward from K Street for two decades.

"Finally, Facadism with Finesse" was the succinct verdict rendered in the headline for an item on the building in the November issue of Architecture magazine. The structure, designed by the Washington firm of David M. Schwarz/Architectural Services, is indeed all new except for the fac,ades of five late-19th-century row houses on the south side of N Street.

With their variety of entrances, bays and dormer windows, these fac,ades are typical of the lively, textured streetscape of the old Dupont Circle neighborhood, and they give the building one half of its character. The sympathetic joining of new elements, rising gradually behind the four-story fac,ades to a full height of eight stories, completes the composition in a satisfying way.

This is a delightful, but not predictable, result. It is useful to compare 1818 N St. to Red Lion Row (2000 Pennsylvania Ave. NW), perhaps the city's best known, and least admired, example of "fac,adism," to find out why the one design works better than the other.

Setting up Red Lion Row as the bad guy and 1818 N St. as the good guy is ironic in one important respect: the Red Lion Row project, with its sleek 10-story office building massed behind a block-long row of lower, older structures, actually preserves more than just the fac,ades of the old buildings.

At the insistence of the city's historic preservation reviewing agency, the Red Lion Row architects (John Carl Warnecke & Associates working for George Washington University) agreed to save the complete original "footprints" of the older buildings. As a result, using in many cases the original rear walls (painstakingly dismantled and rebuilt), they were able to create a fairly interesting, usable space between the old and new buildings. By contrast, David Schwarz (working for the Lenkin Co. and with the city's landmarks commission) agreed to preserve only the fac,ades and the first 15 feet of the N Street houses, and when the sidewalls began to collapse during construction (and subsequently were demolished for safety reasons), he was left, pure and simple, with the fac,ades.

Is this a case, then, where appearances are more important than reality, or, to put it another way, where appearances are the important reality? The answer is a qualified yes. Despite its rather artificial character, the tight galleria space of Red Lion Row is a nice public benefit derived from a decade-long struggle between citizens and the university, but the principal public aspect of the project -- its appearance -- is an unfortunately disjointed blending of a flat Modernist fac,ade and a romantic-looking series of highly modulated older fac,ades. The result is that Red Lion Row, despite its actual depth, looks like a Disneyland stage set, whereas 1818 N St., despite its actual fac,adism, looks like a real building on a real city street.

In part this difference is due to differing conditions on the specific sites involved -- Schwarz really didn't have the option of full-depth preservation on his restricted N Street site, while John Carl Warnecke had to deal with a much bigger building mass behind Red Lion Row. In part it is due to differing architectural attitudes -- by frankly contrasting the style of his add-on structure with those of the older buildings, Warnecke created a very strong image of disjuncture, while Schwarz, by assimilating the historical motifs of the old fac,ades in his new structure, created a strong feeling of unity.

But mostly, I suspect, the success of Schwarz's design has to do with care and finesse: in materials, colors, details and massing, his building complements the fac,ades it stands behind -- it is, in other words, truly a background building.

The soft red brick of the addition, with punctuation marks of rose-toned concrete formed to look like the stone lintels, ledges, porches and parapets found throughout the Dupont Circle district, is quite different from the painted brick of the old fac,ades, but the contrast is very low-key. Similarly, the pediments and parapets of the new construction, though by no means copies of the dormers on the existing fac,ades, have just the right feel.

Then there is the way the new building steps back from the street line in a gradual procession that makes one acutely aware of how very, very politely the architect is treating the street and the old fac,ades. Added benefits of this kind of work are commodious balconies and an appealing, varied silhouette -- no small contribution to a city whose architects, up until recently, have lazily interpreted the height limitation to mean that every building in it should have a flat top.

It should be pointed out, too, that the architect's care extended not just to the primary fac,ade but to the other sides of the building. The eastern edge, for instance, thrusts forward as a wing to give definition to a midblock alley and, Schwarz mischievously points out, to hide as much as possible of a squat office building put up in the mid-'60s.

On the west side, where the new building abuts a colorful Georgianesque mansion on 19th Street (not part of the project but very much a factor in the design), Schwarz took a cue from the way Charles Rennie Mackintosh modulated the west end of his turn-of-the-century School of Art in Glasgow. If the reference is esoteric, the results are straightforward: the Mackintosh piece happens to be quite similar in proportion to the chunk that Schwarz had to design, and the transplant, altered to suit its new conditions, fits right into its appointed place near Dupont Circle.

What happens behind the old fac,ades is, however, a cause for some concern: this is where the fac,adism of the composition is most obvious, because, although the architect provided working doors for the restored fac,ades, it remains to be seen whether the new office tenants actually use them. The unused doors would contradict the pattern of street activity that used to enliven this street, and, to turn the ironic twist one more time, it is where the Red Lion Row project, seen close up, is superior to 1818 N St.

But something must be given up if the attractive order of our older streets is to be given new economic life, and in this case the gains of the compromise -- a sensitively designed new building that speaks to the past and the present -- clearly outweigh the loss. Preservationists who still detest the new project because of the way the walls between the old buildings were destroyed should take heart from this, and also from the fact that the walls and floors were replaced in their original places, providing some very nifty interior office spaces.

"We tried to weave things together," Schwarz says, referrring not only to the old fac,ades and the new construction, but also to the new downtown and the old Dupont Circle neighborhood. Weaving pieces of the city together is one of the great challenges facing Washington's architects and developers these days. It is a trying, complicated, necessary job that Schwarz and his colleagues, working with these particular pieces, did very, very well.