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Restoring a Modernist icon.

Anyone might reasonably assume that restoring an early- to mid-20th-century Modernist house designed by an internationally acclaimed architect would be easier than restoring the late-19th-century house across the street designed and constructed by a local builder. After all, construction knowledge and technology in general would have progressed in the intervening decades, and having one of the great architects of the century focusing his considerable talents on something as simple as a house would surely reduce any problems we might encounter, right? Yet our experience has taught us that just the opposite is true: The Modernist icon is often more fraught with technical shortcomings in its original design and is typically much more challenging to restore than the run-of-the-mill older house across the street. And although any restoration project can pose philosophical dilemmas and technical challenges, these tend to be more pervasive in projects on Modernist icons.

Philosophical dilemmas

The basic preservation philosophy established at the outset of any project often derives from careful consideration of the deceptively simple question: What are we really trying to preserve? With many older, more traditional historic houses, that question is often answered simply, with “the historic artifact.” This leads to a familiar approach that entails preserving as much of the historic fabric (that is, building materials) as possible. After all, the builder of the older house across the street was not trying to lead an architectural revolution, nor was he trying to build the embodiment of a utopian ideal. But the iconic works of Modernism are often iconic precisely because they represent an effort to design and construct the physical embodiment of an idea or philosophy. This gives the fundamental question What are we really trying to preserve? two different, equally valid answers: “the artifact” or “the idea.” The two answers would lead down very different paths involving very different approaches, and ultimately to very different things either being preserved or potentially lost or obscured in the restoration.

Even a task as seemingly straightforward as replacing a severely deteriorated wood 2 × 4 stud is informed by the general philosophical approach established at the outset of the project. With the design of Walter Gropius’ own house in 1938, for example, an important idea was the use of readily available, factory-made, “off-the-shelf” building materials and fixtures for everything in the house, with the sole exception of the stair rail. Because wood studs are a different size and profile today than in 1938, preserving “the idea” of the house might lead us to use an ordinary off-the-shelf 2 × 4 wood stud as a replacement, while preserving “the artifact” might lead us to custom mill new studs that match the original size and profile. During our exterior restoration of the house about 15 years ago, after a great deal of thoughtful discussion of both approaches, the owner and steward of the house, Historic New England, decided to custom mill studs to match the size, profile, and species of the originals but clearly label them as replacements with durable copper tags.

Trying to ask the question “What would Gropius do if he were alive today?” is an invitation to delve into the netherworld of “séance architecture” (a wonderful term we borrow from architect Ann Beha). It simply isn’t a viable basis for restoration decision making.

Technical challenges

Original troublesome roof eave detail at the Gropius House.

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In constructing that run-of-the-mill traditional house across the street, the builder’s lack of aesthetic or technical innovation meant that he didn’t need to invent new technical details of consequence, but rather could draw from the long-established collective knowledge of what had already proven to work well and be durable in the local climate, with the locally available materials. In essence, the major “bugs” in the original design and construction had already been worked out over the course of many decades, with the successful details “surviving” and carrying forward, a process we refer to as “architectural Darwinism.”

But in the Modernist houses, innovation made it necessary for the architect to develop new designs for technically critical details, such as wall sections at window heads and sills, or roof-to-wall transitions. It’s extremely difficult for anyone, even a truly great architect, to reinvent these technically critical details from scratch and not encounter any problems, such as leakage or deterioration. In reality, what often happened was the process of working out the bugs began anew, with the owners bearing the unfortunate burden of “beta testing” the new design and living with the problems.

New detail from the restoration of roof eave at the Gropius House.

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No Modernist house is more iconic than Le Corbusier’s Villa Savoye (1928–31) outside Paris, and the series of urgent distress letters that Madame Savoye wrote to Le Corbusier in the first few years after its construction — complaining of severe roof leaks in many rooms — demonstrate both the formidable technical challenge of inventing new, technically critical architectural details (in this case, for the water-proofing of flat terraces over occupied space), and the unfortunate role of an owner in the beta testing.

Similarly, on Frank Lloyd Wright’s one-story Zimmerman House (1951) in Manchester, New Hampshire, the unvented, minimally sloped clay tile roof directly over a “cathedral ceiling” of heated interior space was a veritable ice-making machine each winter, creating massive eave ice dams and resultant soffit damage prior to our roofing restoration in 1999 and 2000. Our restoration design created a thin, concealed “overdeck” to vent cold air to the underside of the roofing, and thus prevent ice dams, while not disturbing the beautiful cypress ceiling inside.

Original windowsill configuration at the Gropius House that lacked flashing and caused extensive rot of the wood framing beneath the windows.

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Philip Johnson’s Thesis House in Cambridge (1942) currently suffers from the decay of structural wood framing members that are buried below grade — a detail that any carpenter would know to avoid but that derived directly from Johnson’s aesthetic desire to have the courtyard feel like a seamless extension of the interior living space of the house, by making the interior floor and the exterior courtyard flush and avoiding any step-up from outside. Our team’s work involves structurally repairing the decay and implementing concealed waterproofing.

Although the technical problems with Modernist designs are occasionally attributed to shoddy construction or a shortage of quality materials during or between the world wars, we haven’t found that to be true on any of the buildings we have investigated or restored. Rather, the problems we have encountered most often derive from inherent shortcomings in the original design. The Gropius House was no exception:

Windowsill detail as revised during the restoration, introducing concealed metal flashing beneath the sill to address and prevent water intrusion and resulting rot of structural wood framing beneath the window.

Click to enlarge image.

Originally the gravel-stop flashing along the roof edge was a continuous piece of metal flashing (without expansion joints) that joined the built-up roofing membrane in a flood-coated lap. Years of cyclic thermal expansion broke this lap, creating leakage and wood rot.

The window head detail originally included a lead flashing, but the asphalt-saturated felt waterproofing behind the wood siding was mislapped behind the flashing. This is akin to tucking your raincoat into your pants and expecting your pants not to get wet. Predictably, the interior plaster at the window head was deteriorated in locations where water bypassed the wood siding above and reached the felt.

The windowsill detail was the most troublesome and led to the most extensive deterioration. Unlike the window head and the roof edge, the windowsill had no flashing, which was needed to capture window leakage and keep it out of the wall assembly. Further exacerbating the problem was a wood sill profile that almost seemed designed to direct water inside the wall. Predictably, the stud framing beneath the windows was severely rotted and required extensive replacement.

The real techniques and the foremost challenge

When a tour guide at a restored Modernist house mentions a challenging restoration project, the visitor might imagine craftspeople in white gloves and lab coats working with syringes and tweezers, and might think of any required design as being minimal to nonexistent — after all, what’s to design, you are just restoring what’s already there, right? In reality, Carhartt coats and power tools vastly outnumber lab coats and syringes, and the single greatest challenge of the restoration project is often the challenge of design. These Modernist buildings almost invariably have certain innovative original design details that are intrinsic to the architectural expression of the master but that have profound technical flaws inherent in their original design that caused major problems and deterioration.

The question then is not What would the master have done? The existing (failing) detail shows us what the master did; no séance is necessary. The real question and the truly formidable challenge of these projects then is how to succeed where the original design failed — how to maintain the aesthetics and appearance of the master’s original design but completely rethink and redesign the detail, often beneath the surface, in such a way that it finally works. In other words, put away your Ouija board and put on your thinking cap.