50 Shades of Gray: Matching Concrete and the Challenges of Restoring Frank Lloyd Wright's Unity Temple

http://curbed.com/archives/2015/07/31/unity-temple-restoration-frank-lloyd-wright.php

Architecture fans plan pilgrimages to Chicago just to see key works by icons such as Mies van der Rohe and Frank Lloyd Wright in person. Gunny Harboe, an architect and preservation specialist heralded for his work with modern architecture, has had the pleasure of not only working on these masterpieces, but making sure crowds in the future may see these works in an even better state than visitors today. Between his current work on a collection of high-profile Wright works, including the Robie House, to previous gigs replacing the glass panes of Crown Hall, Harboe has overseen multi-million dollar restorations of some of the most famous structures in the country. Currently working on the Unity Temple, a project partially funded by the Alphawood Foundation and a recent Getty Grant (they're still looking for more donors for the estimated $23 million project), Harboe has probably spent more time inside Wright's iconic 1908 structure than anyone except the ministers. Curbed spoke to Harboe about the difficulty of restoring an early example of reinforced concrete architecture. 
How did you get involved in such specialized work?
I've been working at it for a long time; I'm getting to be an old man now. I didn't decide I wanted to be an architect in high school or anything like that, it took me a long time to figure it out. I majored in history in college at Brown, and then worked for a while building post-and-beam houses in Vermont. In college, I was very interested in material culture as an expression of culture and history, and buildings were certainly a part of that. I did some internships at preservation groups, then went back to Columbia University in the early '80s to study historic preservation. When I finished that, I got a job at the Met in New York building the Frank Lloyd Wright Room. That was an epiphany, and then went back to school at MIT to become an architect. And then after that, I came back to Chicago and got really lucky. The first big project I worked on was the Rookery Building, which has a Frank Lloyd Wright lobby in it. That was my second interface with Wright, and over the next 25 years, I developed a preservation resume. I've been working on Unity Temple since about 2000.
What does Unity Temple represent to you in cultural terms, especially after spending 15 years working on it?
Every time I go in there is a joy. I'm constantly reminded of his brilliance. It's an amazing, peaceful, beautiful space. A building like Unity Temple, they don't get any better than that, in terms of being important and being exciting to work on. It's one of the great treasures of America. It's one of the reasons it's part of the Frank Lloyd Wright World Heritage nomination for its importance. It's always been on any serious architects list of places to visit. It's always been appreciated for what it is, but that doesn't mean everybody has always been happy to write a check to restore it. We're grateful the Alphawood Foundation stepped in.
Was there ever a moment where you thought, man, if I am a few inches off on this repair work, I'm going to break a priceless artifact?
I would say that we take the responsibility of doing Wright extremely seriously. It's important to us to do the right thing for the building. It's always the primary focus. We want to make sure we're honoring the architect and the original intent. Especially when it's a Frank Lloyd Wright or Mies van der Rohe masterpiece. It's not that we don't take other building seriously, but something this historic, we take very seriously.
The public always look at the Unity Temple as this design masterpiece, but you also have the perspective, as someone renovating it, of the construction skills that were involved. Are there any stories about the construction that the greater public doesn't know?
That period is such an interesting time, coming off a boom in skyscraper construction. It's not the first concrete building, but it's one of the first. Wright is obviously experimenting with that material and what you can do with it.
What makes this concrete structure such a restoration challenge?
This was built at a time when architects were figuring out to use the material. They started using it for more mundane buildings like warehouses, to build structural elements. Here he's using it as architectural elements. One of the characteristics of this early concrete is that it's rather porous. It's not a solid mass like you think of when you look at the foundation of a house now. It's a very different type of material. It wasn't really consistent and had a lot of voids in it, meaning moisture and water could move through it very easily. We're not sure how early on it started to exhibit issues, but it was pretty early. By the 1970s, the concrete was at a point where they needed to do something about it and they made the choice to reface the building with Gunnite, which is Shotcrete, basically a spray-applied concrete. They resurfaced the whole building and applied the Shotcrete, it's shot on like a hose like when you're fixing a swimming pool. We're repairing the cracks, and the biggest challenge is getting it all to blend in so it doesn't look blotchy. We're going to great pains to do mock-ups and trials to match the appearance of the aggregate. There are little pebbles in it with different colors and different types.
Does this mean sourcing stones and pebbles from different sources?
Yes, but the burden of that is on the contractor. But we know what we're looking for. We went through a whole series of mockups last year, and we're doing it again now that we're doing the actual work. Different areas have different looks. Edges with protruding elements, like sills and overhangs, have more weathering on them, so the aggregates are more pronounced versus areas under the windowsills that have less weathering.
Will there be a lot of specialized artisans and machines working on later parts of the restoration, especially the interior?
It's not as much about the machines, but it's critical to get people with the right skills. All the art glass is all being restored in California by a place called Judson Studios. The guy applying the concrete, it's critical he does it correctly. We did a lot of in situ mockups on the physical building to make sure it's correct. They spray it on and trowel it. It's like clay. If they work it too much, it starts pulling away. When you start fussing with it too much, you can overwork it. It's a lot more difficult than applying paint with a roller. On the inside, all the interior finishes are being redone. The paint finish, as was true on a lot of his work from this era, it's very thin, almost like a wash. It has a visual texture to it that's very soft and subtle and beautiful.




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