Three years before the Farnsworth House was built, its drawings and a model were the centerpiece of an exhibition at the Museum of Modern Art in New York. On display at MoMA in 1947, the model inspired a then youthful architect, Philip Johnson, to design and build his now famous “glass house” in Connecticut. But the Farnsworth House, intended as a weekend retreat for a Chicago internist, Dr. Edith Farnsworth, was and is the genuine article — a seminal work of architecture designed (and built) by a towering figure of 20th century architecture, Ludwig Mies van der Rohe.

Now a museum, it is owned by the National Trust for Historic Preservation and managed by the Landmarks Preservation Council of Illinois, which took control of the building in a Sotheby’s auction in 2003 for $7.5 million. In the custody of true preservationists, every piece of the building — which is so simple looking as to leave an observer wondering how difficult it would be to preserve a structure that is mostly glass, steel and marble — has been analyzed with an eye toward building a long-term schedule of restoration and preservation.

Whitney French, who manages the site for the Landmarks Preservation Council, says the schedule includes a complete rebuilding of the distinctive travertine marble decks, which are composed of several layers of gravel and porous vermiculite sandwiched between the tiles and a frame of precast concrete and steel. At issue, drains located underneath the outdoor decks have long since corroded and have become clogged. Basically, the decks need to be taken apart and rebuilt.

Other parts and systems of the home are also slated for various grant funded projects. A flat roof, which Mies designed, drained to the middle and down through the center core of the house. A reroofing during the 1970s increased the grade toward the center so as to evacuate the water more quickly. Now preservation experts are at odds over which roof to replace. A new roof is clearly needed, but two camps of preservationists face a choice — leave the current leak-free solution in place or return to the design of the master, which was also leak-free but worrisome to many because the grade is likely not enough to handle a true Midwestern gully-washer.

“One camp feels that every part of the original should be restored, including the roof, which is not part of the visual experience,” notes French. “The other school of thought is to keep the current type of roofing solution in place, even though it is not the original design, because it is doing a good job of protecting the rest of the structure.