“I want you to live with the waterfall, not just to look at it, but for it to become an integral part of your lives.” So wrote architect Frank Lloyd Wright to the Kaufmann family in 1935, just before construction would start on Fallingwater, which famously cantilevers over a cascading stretch of the Bear Run stream in rural southwestern Pennsylvania. Wright’s ingenious fusion of nature and architecture, completed in 1937 and honored as a UNESCO World Heritage site in 2019, owes its existence to the power and presence of water. He even utilized river pebbles in some of the building’s concrete mix.

That same element has, over the decades of the home’s storied existence, conspired to degrade it, seeping into walls and even on occasion flooding the living space. In 1956, a roaring Bear Run ran into the living room during a severe storm while owner Edgar Kaufmann and his family were inside, leaving everyone unscathed but significantly damaging precious artwork. And it’s not just the nature of the site. Wright’s insistence on certain materials and design choices, across his entire body of work, have famously created maintenance challenges and water intrusion issues for owners for decades.

Maintenance and restoration projects have tried to strengthen Fallingwater’s defense, attempting the tricky balance of defending it from environmental challenges while adhering to increasingly stringent preservation edicts. One of the most exhaustive, a $7.5 million, three-year effort that put scaffolding around the entire home for the first time in 20 years, is now at the finish line. Here, lead restoration architect Pamela Jerome, the president of New York–based firm Architectural Preservation Studio, shares the challenges of restoring what might be the most famous home in existence.

What exactly is the scale of damage at Fallingwater?

Pamela Jerome: Fallingwater is in great condition for a modern house of its age, the result of cyclical maintenance and ongoing careful stewardship. However, the greatest area of concern were the leaks on the third floor of the main house. In addition, warranties on existing roofing had lapsed, necessitating replacement of all roofing and terrace waterproofing. There were visible places of water damage that required attention, and grouting and waterproofing replacement allowed us to resolve these areas of concern.

Where is the water damage mostly happening?

Since ancient times, stone walls have been constructed in a similar fashion [to Fallingwater], with an inboard and outboard wythe, and bits of stone and mortar packed as infill into the middle. At Fallingwater, periodic through-wall tie stones hold the two wythes together. Over 90 years of water have passed through Fallingwater’s stone walls due to a lack of original flashing. This has caused a lot of the infill materials to settle and/or wash out of defective joints.

Buildings are normally constructed with metal counterflashing wherever exterior walls meet a roof or terrace. It’s located a minimum of eight inches above the finished roof or terrace so it is visible. Presumably, Wright did not like the look of what would have been copper counterflashing. But without it, any moisture entering the stone walls can penetrate the interiors. In Fallingwater’s case, because the walls also have projecting ledges that accumulate snow and rain, this tendency is exacerbated, allowing moisture to seep through hairline separations in the mortar joints. As a result, most of the chronic leaks were associated with water coming through stone walls.

How much damage is done to the home from precipitation versus Bear Run?

Bear Run can flood. There was a well-known event in 1956 that brought water up to the level of the living room, overwhelming the east and west living-room terraces. There has been debris brought down by Bear Run that knocked out part of the stairs to the stream. However, the main damage within the buildings comes from precipitation entering through the ledges projecting from the stone walls, whether that be rain or melting snow.

Did Wright leave any instructions, advice, or suggestions on maintenance and upkeep of Fallingwater?

No, Wright left no advice that the Western Pennsylvania Conservancy [which owns and operates the home] is aware of. In fact, he reassured the Kaufmanns that the house was sound. The Kaufmanns had a caretaker, as they did not live at Fallingwater year-round, who was responsible for the grounds as well as the maintenance of the buildings. Considering the size of Fallingwater’s team today (110 total, 11 maintenance staff), it would have been a challenging site to care for even when it was newly constructed.

How did you locate the water damage, compared to the last time the home was updated?

Laser-scanning has been a game changer in terms of producing accurate AutoCAD background plans, elevations, and sections. For the first restoration, our CAD drawings were developed from hand measurements. For this one, we used surface-penetrating radar along with videoscopes to locate and calculate the size of voids in the stone walls as well as to determine how continuous the voids were. Additionally, smartphone apps that perform laser-scanning were used to quickly understand thicknesses of stone walls.

You said despite working on renovations here before, Fallingwater still surprises you. What were some of the biggest surprises this time around?

One of the biggest was just how hollow the stone walls actually were (which could fill with water). Another surprise was finding an unwaterproofed slab between the guest house and boiler room with a stone parapet above. Everywhere else, the stone walls continue through the roof and into the interior, whereas in this one location, the parapet stonework is not continuous with the stonework in the rooms below.

In addition, we found large hollow chases inside two other stone walls, which may have been meant for mechanical or electrical, that we ended up grouting around. Another surprise was understanding how much structural work the stone pier at the north end of the enclosed bridge is performing, something we had not considered during the restoration we did from 2001 to 2004, when the structural interventions were mainly focused on the post-tensioning of failing cantilever beams.

In terms of cost, can you broadly break down where the $7.5 million in the budget is going?

The majority of the cost is going into skilled labor. We are utilizing specialty contractors, most of whom are familiar with the site and its conditions, having performed maintenance projects and/or mockups prior to this restoration. For instance, the scaffolding companies needed to be familiar with the strength of the waterfall and the conditions that occur when the stream and waterfall freeze. The roofing contractor had to be certified by the roofing manufacturer in order to apply their products. The masons needed to know how to work with the existing concrete. Most of the skilled contractors, many of whom have experience with Fallingwater, are from the Pittsburgh region.

This repair work obviously feels so much different than that of a typical family home. What makes it more difficult to work on?

Fallingwater is a challenging site to work at; the site remained open to public visitation throughout the restoration work, with the bulk of the work being performed during the winter months when the site is closed to tours and when the weather is not suitable for curing temperature-sensitive materials. Fallingwater’s location is remote and local skilled labor was difficult to come by.

It is also part of the 5,100-acre Bear Run Nature Reserve, also owned and managed by the Western Pennsylvania Conservancy. There are lots of restrictions. As the site remained open to public visitation on its normal schedule, there were also restrictions as to when noise could be made and what kind of clothing could be worn by the contractors. General policies regarding food, drink, and smoking also were imposed.

Fallingwater projects over an “Exceptional Value”-designated stream, meaning that it has the highest grade of clean-water quality in the state. No construction debris is permitted to enter the stream, so every operation must be strictly contained and monitored.

How much better will the home perform, in terms of water damage, going forward? And is the idea of making it leakproof tenable, considering how Wright built it?

Unfortunately, Wright’s choice of large river pebbles has caused two issues. The first is that a cement matrix does not stick as well to rounded stone as it does to broken stone, so this causes debonding. The second is that river pebbles tend to contain more chert than is typically permitted for concrete aggregate. As a result, Fallingwater’s concrete is cracking due to alkali-silica reaction, or ASR, and the only way to remedy it is to remove and recast or exclude moisture penetration. We have done more recasting during this project than the last one. We also changed our base-flashing detail for roof-roll edges, this time covering the complete half round with waterproofing. That will help stop cracking of the exposed roof edges, but there will always be cracking of the original concrete because of the presence of ASR.

The goal of grouting the stone walls was to make it more difficult for liquid water to enter the houses. However, grout is not waterproof and will not eliminate moisture entirely, so damp spots may still manifest at the interior stonework because of the lack of through-wall flashing. Finally, we have been extra cautious with our waterproofing details to ensure it isn’t compromised. Between the various architectural and structural interventions executed this time, we expect the buildings to perform much better than they have been.

What does success ultimately look like? How would you evaluate your performance to that end?

Success for us is eliminating leaks, protecting the interiors and art collections from water intrusion, conserving original steel windows and doors, and ensuring that Fallingwater is structurally sound for future generations to enjoy.

Top photo by Jonathan Cohen/Alamy

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