An expensive and painstaking effort is under way to reconstruct an elegant beaux-arts mansion on Embassy Row that was destroyed in a spectacular three-alarm fire last year.

Architects and workers using photographs and floor plans of the building at 2201 Massachusetts Ave. NW that was called the Argyle Guest House when it burned "are trying to do as best justice to the building and its original character, design and detail work as possible," according to a spokesman for the owner-developer, Bruce H. (Scott) Mcleod. He called the project "an act of love."

The mansion, designed by Paul J. Pelz, the associate architect for the Library of Congress, was built for Navy Capt. Frederick Augustus Miller in 1901.

On Sept. 5, 1984, as it was being renovated and remodeled to hold nine condominium apartments, flames roared through the structure, gutting the interior, destroying Ionic columns, parquet floors, ornamental wood carvings and decorative friezes, many of which had nautical themes.

Fire officials estimated the damage at $2 million and said the blaze was started by an arsonist, but no arrest has been made.

Macleod's spokesman said the original renovation plan is being followed and completion is expected in about two months. The condominiums will be priced from $130,000 to $300,000, he said.

Pelz's original floor plan is being followed, "retaining the granduer of the bay rooms, the grand staircase and the high ceilings," the spokesman said. He said plaster molds have been used to copy the original trim work of doors, windows and ceilings, and that "grand, turn-of-the-century wooden mantelpieces" for the fireplaces have been purchased from other beaux-arts-period buildings to approximate ones destroyed in the blaze.

Fire also destroyed much of the decorative terracotta stonework on the outside of the building, which is prohibitively expensive to replace, the spokesman said. He said designers are working with companies that have developed a special technique to produce a terracotta-like substitute.

In addition, he said, only one quarry, in Ohio, can produce bricks the same color as those used to build the mansion. However, he said, the quarry does not have molds to make bricks the same size as the originals and workers have to cut about an eighth of an inch off each one.

A stone carving of a cat, which adorned the southwest corner of the roof, was found in the fire ruins and will be replaced when the renovations are completed, the spokesman said.

Most, but not all, of the renovation costs are being borne by insurance, the spokesman said.