Stone in architecture: a look at the practical issues
During a roundtable discussion at the firm's offices in Atlanta, several members of the staff discussed their experiences with these issues. Participants included the following:
Joseph Greco, AIA, LEED Accredited, Principal
Richard E. Robison, R.A., C.C.S., Principal
Antonin Aeck, FAIA, Principal
Susan M. Turner, AIA, Principal
Mary Catherine Martin, AIA, Senior Architect
SW: What are some of your positive experiences of working with stone? Can you point to any projects that pleasantly surprised you?
Robison: We have had lots of positive experiences. The Georgia Public Health Lab is one. This building, like so many of our buildings, has a fairly customary institutional budget. When we make use of stone, we're doing so in the context of a â€œstandardâ€ publicly funded budget. In other cases, it's a privately funded budget, but they can be as conservative and as tight as a public project.
There are numerous examples of stone. The Georgia Public Health Lab used granite scrap as we mentioned. We're doing another public health lab for the state of Georgia. We've used â€œDuke Stoneâ€ at Duke University -- we wouldn't use anything else there.
At Duke University, we completed a high-tech research laboratory called the Genome Sciences Research Building II. Of course they have a mandate that you utilize â€œDuke Stoneâ€ in all of the buildings -- at least to some measure. In this case, we used it at the lower levels to create some of the tower elements and interest elements of the building. It works in with a cast stone and pre-cast system and picks up some of the other colors and patterns on campus, but in a bit more contemporary and a little more interpretive way.
SW: How about negative experiences, where something just didn't go right? Has there been a stone project that you look back at and wish you used a different stone or detailed it differently?
Aeck: We had an experience years ago on a building where we actually worked with an outside specification consultant, because we hadn't used a lot of stone veneer. It was at a period of time when the old mud-and-wire techniques were evolving to more mechanical fastening techniques. I don't think they served us well in what they specified. When we subsequently expanded that building, we utilized more contemporary methods, and that worked out quite well. I think we saw both sides -- how well it could work and what doesn't work.
Also, I think in the early days of thin stone, some of the veneers were just too thin. They were trying to sell material probably for cost reasons and as a result, they tried to do things that were probably too aggressive.
Robison: And we're fortunate that in this respect our buildings tend to be two, three, five, six stories tall, and so we didn't have the negative experience of the 20-, 30- or 40-story office buildings where the very best and the brightest architects and engineers and stone consultants were trying to do more with less in shorter times with less weight, and learned some things in the process of doing that. We weren't on that learning curve ourselves.
Greco: There's a fair amount of historic stone that we deal with. I think by and large we use more of a masonry type configuration for stone rather than a thin hung panel. We have a few examples where it is panelized stone, but those are obviously the ones that have had the more known problems.
Aeck: In the 80s, we had a sister company called CAD Shared, which offered computer graphic services. We got a contract to write a stone shop drawing program, and we got a good dose of how complex it can be to address all of the needs of such a system, and we gained a healthy respect of getting it right.
Martin: The only time I have seen something negative with stone was when it was either installed improperly or it was asked to do something that it wasn't really supposed to do. When we see it in the Historic Preservation studio, it's at least 100 years old, and every time there is a problem there is a design or installation issue behind it. I think every time in the Georgia State Capitol when we had a problem, it was a poorly placed anchor or something like that.
Robison: And those have been few and far between.
Martin: They have been. I mean the quality of that stonework was exemplary in general.
SW: How do you go about sourcing stone for your projects? Do you have a library here or do you have reps that come visit you?
Aeck: For our types of projects, it is the contractor who actually sources the stone. Our projects usually don't call for an exotic stone from a very specific remote locale. The contractor will find which granite or limestone source he's going to get.
SW: In that case, would you specify essentially the type of stone and color range?
SW: What would you say would be the biggest challenges of working with the stone industry?
Robison: For me, the big challenge is one of inheritance. When the stock market crashed in 1929, monumental building in the U.S. -- and indeed virtually throughout the world -- came to a halt. It was followed by 10 years of the Great Depression. It was then followed by five years of World War II, and then it was followed by a few years of getting back on our feet and everyone trying to get back home and get a job and resume their normal life. The long and short of it is, as architects and contractors and masons, we lost a generation of continuity. There were all but no monumental buildings done during a period of 20 or 25 years. And by the time that all restarted, the world had moved on. We were into the contemporary age or whatever you want to call it, and buildings did not look like buildings that were done in the 1920s. Ornamentation was out and modernism was in. Stone, as well as all other materials, were asked to do different things. Heating and air conditioning was in. So on one hand, you have a disconnection in the memory -- both as the designer as well as the stone carver, etc. On the other hand, you have a disconnection in technologies. You have completely new technology -- completely new demands such as thermal moisture or load structural. So there is this tremendous learning curve to try and remember what we have forgotten, and to learn what we now need to know in order to go forward.
SW: How difficult is it to keep stone in the budget when it comes to value engineering and assessing what a building is going to cost per square foot?
Greco: We do a pretty comprehensive job of budgeting our projects. We have a good handle on what stone actually costs. We found that in the right applications, stone can be a fairly economical material. So that our buildings are not subject to value engineering, we usually try to make stone an integral part of the building that is not just an applied finish that can be substituted for vinyl tile or something like that. By making it an integral part of the architecture, and by choosing your dollars wisely around the entire building, you can usually make it part of the project. In some cases, pre-cast costs and cast stone costs have gotten very high. We used to think it was more economical, and now we are seeing those numbers high enough that other options become more possible.
SW: What is the feeling among people who advocate â€œgreen buildings.â€ Is stone seen as a material that is not a renewable resource that's depleting the earth or has it not been thought about that way? On the other hand, in terms of using energy, stone doesn't require much energy to dig out of the ground and to process. What's the feeling on stone as an environmental material?
Greco: It's a complicated thing because LEED actually looks at a lot of different aspects of it. Stone that's coming from 6,000 miles away has a different environmental impact than one that is local. Certainly anything seen as scrap or partial scrap or an indigenous material is seen as a very sustainable product. You're right, it uses a lot less energy than brick and other masonry products that have large concrete production processes that aren't environmentally friendly. So I think that if you can get the material close, and it's sort of a smart low-tech material, then it's very sustainable. We feel it is.
Robison: And it also makes sense if you look at the longevity of a material. I'm not going to say that the pyramids are still in use to a vigilant function, but they are still standing. If you look at buildings throughout Europe as well as many other parts of the world, there are buildings that have been in continuous use for hundreds and even a thousand years. Those uses may have changed over time, but they have been continually used; that's pretty sustainable.
Greco: On one hand it's good to recycle materials, but the very best thing you can do is to recycle a whole building and keep using it.
Robison: And in the case of any number of cathedrals, castles or monuments around the world, when one empire falls and the next one takes over, they take the stone from yesterday's gods and build new buildings with it. So it's completely recyclable in that sense.
Aeck: I heard the director of planning mention the other day that the average age of the buildings at Duke [University] is 65 years.
Greco: At Duke University, we recently completed a high-tech research laboratory called the Genome Sciences Research Building II. Of course they have a mandate that you utilize â€œDuke Stoneâ€ in all of the buildings -- at least to some measure. In this case, we used it at the lower levels to create some of the tower elements and interest elements of the building. It works in with a cast stone and pre-cast system and picks up some of the other colors and patterns on campus, but in a bit more contemporary and a little more interpretive way.
SW: How much do you get involved in selecting the installation products for your projects?
Martin: In one of our preservation projects, we are working on a fort called Fort Jefferson. It's a 19th century fort down in the Gulf of Mexico -- about halfway between Key West and Cuba. This is supposed to be the largest brick structure in the western hemisphere. It is absolutely massive. To make the mortar for this fort match the mortar that was used there originally, we are actually going to be firing a Rosendale limestone, which is a specific limestone found in New York State. It was the limestone that was fired by the military through the 19th century for the fortification building. It's a very weird roundabout thing -- and these quarries have been closed -- but just through my association with different masons in the country, one of those masons has actually bought the rights and is going to start mining that stone and firing it again, because there are so many of these buildings. Also, many of the buildings in New York City used Rosendale. They are going to start producing this again. It's a natural American cement that hasn't been in production since 1927.
SW: That's interesting. So there's no problem restarting the quarry or extraction?
Martin: No, there's plenty of stock there. It was shut down really through competition. Rosendale cement is not viable as a modern construction material, because it behaves as an older cement. It has a much longer setting time. In the way they build today, they want to go in quick. They want to get strength in 24 or 72 hours, and then they are gone. These mortars and cements aren't going to reach strength for six months to a year. So it's a very different material, but when you are doing restoration work, it makes sense to use it.
The stone used here is limited to the casemates, which are room openings. In the floors of the casemates, they actually used these slates that are about 8 inches thick. The slate flooring there is the thickest slate that I've ever seen in my life. There are also a lot of stone headers. They used stone very selectively in these forts -- usually at entries or more honorary areas.
SW: One of your ongoing projects is the Martin Luther King Federal Building in Atlanta. Can you describe your work there?
Turner: The Martin Luther King Federal Building was originally built as the post office, and it's owned by the U.S. General Services Administration. We're working currently to rehabilitate it for their Southeastern regional headquarters. There are a number of problems with the stone that resulted from shelf angles that are deteriorating and causing movement in the stonework. And so a large part of the restoration project is the restoration of the exterior stonework. In addition to that, we are doing interior restoration of the lobbies and the corridors and rehabilitation of several floors of offices.
Martin: It's a marble-clad building built in the late 1920s. It really hasn't stopped being a masonry bearing wall building, but it's not quite a reinforced beam building. So you have the present beam system that is actually tied to the masonry system. It was really just a transition of technology. I'm sure you see this in other buildings of that era, where you have a real fight between the two systems. That's exactly what we saw there -- sort of an overly tight and rigid structure and lots of things that are tied together that expand and contract in different ways. So our treatment has been to go in there, and in a sense, allow for some of that movement to put in a more flexible anchoring system. But we also wanted to leave much of it intact -- to keep as much of the tight bearing ball and positive aspects in place and make the moderate modifications that we need to make. We need to get rid of those shelf angles that happen to be rusting and expanding. We're going back in with stainless steel.
Aeck: This building started life as a post office, and somewhere along the way someone decided that they should seal up the shelf angles, and they entrapped the water that obviously penetrated the masonry, and that actually created the oxidation problem as much as anything.
Turner: We looked at two parallel approaches to doing the stone restoration. We considered a total removal scheme where we would systematically -- area by area -- take down all the stones, make the repairs that are necessary, and put them all back in place. We also considered a selective removal where we would only take out the essential bands of stone that are in front of the shelf angles. We did cost analysis com-parisons on them and constructability comparisons, and ended up opting for the least evasive, which was going in and just doing the selective removal.
SW: What other restoration projects are you involved with right now?
Martin: Fort Washington is on the Potomac River outside Washington, DC. We've been involved with an extensive conditions assessment there. This fort was built in response to the War of 1812 when the British went out and burned down a lighthouse. This has several different types of stone. Most of the base of the entire fort is rough gneiss and a sandstone that has weathered very extensively, but is still in very good shape. We don't see any problems with the stone. The only problems that we do see are inappropriate repairs or interventions that have destroyed the original drainage system. There was this very extensive and sophisticated brick drainage system that went in throughout the fort. It was destroyed, and there is a lot of water retention in the fort. On top of that, they came back and repointed with very hard modern mortar that is impermeable. So not only was the water blocked, but it was held into all the masonry.
SW: Can you tell me about some of your renovation work, where you have added new stonework to an existing building?
Greco: We did some renovation work at the University of Alabama at Birmingham [School of Dentistry]. This is a 1950s building; an old deco style building. We did renovation work throughout the building, but we added the front piece, which is a new entry lobby that previously had an entrance that was not ADA-compliant.
Robison: We added that as well as a large stone tower that was created as a stone pop-out as well as the art deco glass and metal wall.
Greco: There, we weren't exactly trying to match [existing stone], but to create something where the whole design was compatible. Indiana limestone was used.
SW: Have you done other work where you added stone to an existing structure?
Greco: The North Atlanta High School was an unusual building in that it was a rather non-descript brick building that had probably been added on to about three or four times. Our task was to double the size of the high school -- they had actually combined two different high schools into a single one. Our architectural task was to try to unify the building and give it a street presence. It sat roughly at 38 degrees to the street. It had to be a durable building, and the existing building was brick. We actually wanted to create a little bit more of a college feel about the building, so we introduced the stone as another material. Stone is also brought into the interior of the building at the cafeteria.