Fallingwater is owned by the Conservancy of Western Pa. Its a 501 (c) 3 corporation and, as such, is run entirely by the funds generated by the Foundation and the Conservancy and a generous endowment from the original bequeath of the Kauffman Family.
There are many on the registry of Historical Places and the Fed Govt hasNO ability to affect any repairs. The registry is a vehicle to induce restoration by tax incentives only
I think that the masons and "mud men" that the Fallingwater Foundation has on staff WILL soon get to the task of repairing all the spalling . I asked a docent and she stated that the list of "honeydo's" is quite extensve because building a house in a rock slope that is erosionally and geotechnically challenged as well as having its environment be a stream complete with a mist generating waterfall is not good for longterm upkeep.
ALL the Frank LLoyd WRight Furniture inside had (at one time or another) been reconstructed exactly to original dimensions and is now built of heavy stock marine plywoods (for stability) covered with walnut veneer. The original solid walnut woods had long ago been warping and so these were quietly replaced. The windows are all mde of a steel frame covered with Wrights favorite red paint and these are slowly deteriorating. as well as the concrete seatings within which they stand. These things are scheduled on a basic replace/repair/or mask campaign. AT present, as we qere told, the task is to mask as much with a modern epoxy with cement dust incorporated within so that any furthetr deterioration os noted and a more stable cosmetic repair is affected until at some time that an entire three or four story segment of windows can be replaced with TITANIUM which will not oxidize as quickly as steel. All they do now is scrape an repaint, scrape and repaint
There is plenty of funding available and the Foundation writes and publishes several master reports of restoration of this important building. They dont keep the repairs a secret(in fact they celebrate them) and I hope I didnt come across sounding like the building was in a "falling down water" state of bad repair. Its just that , since the house is maintained as Wright and the KAuffmans wanted, the outside living was more important than the inside living (the bdrooms are really monastic when you look at em) and the living rooms ALL beckon one outside by various tricks in design and construction. This makes the living inside quite uncomfortable on very warm summer days (Imagine a hot day with very humid consitions from the stream spray). Once yu get outside onto the shadowy balconies, the water spray is actually quite cooling, and they never put AC in the building ecept for the new "Servamts wing and carport area" that was added on in the 1940's. This are houses the kitchen, the servants bedrooms and the garages. The KAuffmans wanted nothing to spoil their building that drove one outside in all seasons
Sad as it is, WRight was an ego driven architect who had very few skills in engineering, so from the get go, he failed to properly anchor the house (this had to be dome as a retro task in the 60's) he didnt understand creep and fatique (this led to the major restructuring of the main cantilievers in the 1990's) That task closed Fallingwater for about a yeart almost 15 MILLION bucks (the whole house cost 150K total between 1935 and 1947 including the purchase of the 1500 original acres).
Also Wright was ignorant of hydraulics and seepage , so Fallingwater, as most of his "Prarie style" buildings ----LEAKS . . The Foundation did restructure the flat roofs with some slight pitch so the layer of stones could catch and allow rain to filter away within a day after the storms were over. Before that, the inside plasters were exfoliating wherever there was a ceiling fixture.
Wright was a real design genius but he didnt trust engineers and he was certain he knew better. The upkeep of a building like Fallingwater is a huuge investment. Fallingwaters "sister" house, also designed by Wright for another client in tge Laurel Highlands of PA is called "Kentuck Knob" It too is owned by the Conservancy and is a bit less outrageous than Fallingwater.