The Official Publication
of the Mason Contractors
Association of America
If there is anything typical in restoration, it is perhaps that nothing is typical. Things rarely turn out to be as they first appear. this challenge is both exciting and satisfying when the project is complete. This is certainly true in the case of One Shell Square, in New Orleans.
One Shell Square was built in 1972 and was, for several years, the tallest structure in Louisiana. The building is a 52-story, double tube system, with a steel core and concrete perimeter. The exterior cladding is in Italian travertine with bronze insulated glass units set in a structural gasket. It was the first southern skyscraper to reach 200 meters in height, and has a total square footage of about 1,732,000 square feet. The restoration project started life in 2004 as a Panel Stabilization/Caulking job, but after Hurricane Katrina in August of 2005, it became a catastrophic, multi-disciplined restoration endeavour.
As is correct procedure, the consultant first tested and verified the suitability of using the most economical solution for panel stabilization, helical wall ties. Travetine from the building was shipped up to the consultant’s office in Dallas, Texas, and tests were conducted to establish the optimal tie diameter and drilling technique to maximize the pull-out capacity of the tie in the stone.
Helical wall ties are the most cost-effective way of retrofitting a connection between the veneer and the structural back-up of a building. The system entails pre-drilling a pilot hole though both components of the wall. Then, using the hammer action of an SDS hammer drill through a special installation tool, the helical tie is driven into place down the pilot hole to make a threaded connection, rather like a self-tapping screw, between the two wall components. No torque is applied during this operation, and the possibility of over-torquing and stripping the thread is, therefore, eliminated. Since the size and form of the tie and the material itself are a given, the only variable is the pilot hole diameter. Varying the pilot hole diameter to optimize the tie pull-out capacity is really the issue when conducting such testing. As a rule of thumb, the softer the material, the smaller the pilot hole required. This, like most engineering, is just common sense. Hard material is more difficult to cut, and the helical tie has the propensity to “ground out,” rather than cut a thread form through the material. Similarly, a softer material needs more bearing surface on the thread form to achieve an equivalent pull-out load bearing capacity.
The travertine stone from One Shell Square is considered a relatively soft material, and because of its inherent pourosity and hidden fissures, a 10-mm diameter helical tie was found to consistently produce the best results. After a series of tests in both wet and dry stone, an installation protocol was established for the travertine, which consistently achieved a pull-out load bearing capacity of between 900 and 950 lbf. Setting helical ties in poured concrete almost always generates a pull-out strength in excess of 1,000 lbf, so an ultimate connection strength of 900 lbf, with the travertine being the weakest link, was established as the design parameter. The die was cast, the specification written, and the job was bid.
After the contract was awarded, mock-ups were performed on the building. Unknown to all parties at the time of undertaking the initial series of tests, poured concrete in Louisianna, is the hardest concrete to be found anywhere in North America. A little puff of white dust while setting the helical tie through the travetine and into the poured concrete could easily have been overlooked. But that tell-tail puff of white dust evidenced the destruction of the thread form in the travertine as the the tie vibrated while being set in the hard concrete backup. This required further investigation.
A travertine panel was removed from the building and mounted on 2 X4 boards, so that once a helical tie had been fullly installed, the tie could be cut, the stone removed, and a load test conducted. That little puff of white powder translated into a reduction of the pull-out capacity of the travertine from 900 lbf to 400 lbf. If a safety factor of four is applied, then the design strength of the connection between the stone and the concrete back-up became 100lbf, which on a 52-story building in a hurricane zone, is a little too close for comfort. Clearly, another solution was necessary, one which would not have a hugely negative impact cost-wise, since the contract had already been awarded based on the original design.
A torque-activated mechanical anchor was modified to enable it to expand within the body of the 30-mm thick travertine stone, while enabling it sufficiently below the surface of the stone to enable a patch to be applied to complete the repair. A series of tests was conducted with this anchor in both the travertine and the poured concrete back-up. The results showed a pull-out capacity in the travertine of about 1,500 lbf, and in excess of 2,500 lbf in the concrete back-up. Work then commenced installing this new anchor system. Only two lengths of anchor were used on the whole building with any variance in the cavity between the stone veneer and the structural back-up be accommodated by over-drilling into the concrete and setting the anchor deeper. Bore-scope analysis showed positive engagement of the anchors in both the travertine and concrete back-up.
Hurricane Katrina swept through New Orleans in August 2005 and quadrupled the scope of work as the protocol changed to ensure that all veneer panels that appeared loose were anchored as an emergency repair. Due to the instability of the travertine panels and the glass, the entire building had to be roof rigged. This entailed the utilization of a custom engineered and installed tower scaffolding system in order to make all stage moves from the top of the building. Naturally, the additional cost of this work caught the attention of the insurance companies, and they brought in their peer review engineers to review the work being done. The anchor system passed with flying colors.
In addition, all of the travertine panels had to be removed from the tower penthouse due to storm damage. A new engineered system was developed and 1,128 pieces of new stone were installed and secured using a mechanical torque activated anchor in the CMU back-up. The panel itself was sandwiched between a recessed wide flanged nut, and a stainless steel toggle on the back of the stone. This effectively transferred both tensile and compressive live wind loads through the anchor into the structural back-up. This will also ensure that the stone panels will remain secure during future hurricanes, and that means peace of mind.
The consultant for the project was Stone & Glazing Consulting, the restoration contractor was American Restoration Inc, and the anchor systems were supplied by Blok-Lok Limited, a Hohmann & Barnard company.
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A Few Bucks of Prevention
Before it was over, those leaking windows turned into a nine-month, $1,750,000 remediation nightmare. It included a total re-cladding and numerous other repairs, and the replacement of its copper fabric flashing with a product that didn’t even exist when the building was being designed.
Since settlement negotiations are still in progress, the complete details of why this brand-new building could need so much remediation are hard to come obtain. However, some background information from the building’s architect, Edwin Elberson, AIA, a principal of Somdal Associates in Shreveport, La., was available. (After designing the building in 2000, Elberson handed off the project to a colleague, but returned to oversee the remediation.)
“When wetness was discovered at the window heads,” Elberson says, “it became apparent that the windows hadn’t been flashed.” He thought it was no big deal, and that some brickwork could be removed from around the windows, flashing installed, everything replaced, and it’d be done.
But the state’s inspectors for this project suspected that the leaking windows could be just the tip of a larger iceberg. So, they insisted on having all the brickwork removed, and they eventually prevailed.
“Frankly, I’m glad they did,” Elberson says. Then he lists some of the workmanship flaws that were uncovered when the building was stripped of its brick veneer.
“Lap-joints on the copper fabric flashing were erratic, and often weren’t adhered properly. The flashing had been cut too far back from the building’s face, leaving no drip edges. The cut-back flashing wasn’t adhered adequately, leaving space for water to enter the building. The heads of the lag-bolts holding the ledge angles had often punctured the copper flashing. Many of the ledge angles didn’t meet properly, either, creating gaps for water to pass through.”
His solution: “We welded the gapped ledge-angles together wherever possible, but we still had to replace perhaps 15 percent of them. Then, we installed TotalFlash in place of the poorly installed copper flashing. Finally, we replaced the brick veneer.”
Note that there was just one new ingredient in this mix: TotalFlash, the “all-in-one” flashing panels made by Mortar Net USA. Why the change from copper flashing? “Back when I was designing the building, TotalFlash hadn’t been invented,” Elberson explains. “Otherwise, we might have avoided most of these problems.
“TotalFlash’s ‘automatic’ overlaps were a huge plus,” he continues. “So were the multiple drainage elements and the stainless steel drip edges – all of them built right into the flashing panels. It also installed more neatly than anything else I’d seen, making it extremely easy to inspect.
“After what we’d been through with this building, I needed the most dependable moisture control, and I needed it installed quickly. TotalFlash gave us both.”
To install the TotalFlash, Elberson turned to a 60-year-old company that had never touched the product before.
“It was no problem at all,” says Russell Bagwell, owner/manager of Thomas & Parker, in Shreveport, La., which specializes in waterproofing and historical restoration. “Mortar Net USA gave us lots of help, even though the product is so user-friendly that we would’ve figured it out pretty easily ourselves. They even sent a couple guys to give us on-the-job training. They were terrific people to work with.”
He says the job went smoothly. “From the start, we were installing each 5.5-foot panel in two to four minutes. Once we got a system down, it went even faster.
“I was a little worried about those bolt-heads that had punctured the copper flashing, but the 40-mil. panels covered them easily,” Bagwell continues. “Since the building was bare, we used the regular-sized TotalFlash panels. But I learned it comes in sizes for restoration jobs, where we just remove a few courses to install the flashing. We’re using it on another job right now.”
Perhaps surprisingly, Mortar Net USA itself has mixed emotions about big remediation jobs like this one. On the one hand, Earl Bickett, general manager of the Gary, In., company, is definitely happy that TotalFlash can help buildings acquire a new lease on life. “Everyone’s trying to extend building longevity these days,” he says, “which means making sure the exterior walls don’t fail.”
What bothers him, though, is the environmental cost of tearing apart a brand-new building. He says, “Just think of the energy it took to make all that brick, and then transport it to the jobsite. Having to do it twice is a downright shame.
“Sure, I’m glad we can help put buildings like this back into long-term service,” Bickett continues. “But like Mr. Elberson, I’d rather see the moisture protection done right the first time.”
Whoever foots the bill for that $1,750,000 remediation job would probably agree.
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Quikrete Supports Transformation of Historic Jail
Historic Boston jail restored and
Since the property was situated in the heart of the Beacon Hill neighborhood, city historic and development organizations sought to renovate and preserve the building, which at one point was an international model for prison architecture. Cambridge Seven Associates (C7A), a full-service architectural design firm, coordinated efforts to preserve much of the original architecture in converting the jail into the modern, upscale Liberty Hotel. Phoenix Bay State Construction Corp. (PBS Construction), a historic masonry restoration company in Boston, aided in the conversion of the 157-year-old jail and building of a new, 16-story, 280-room tower situated behind the old jail.
In renovating the jail, the goal was to maintain the existing granite block exterior and preserve as many interior brick walls as possible. In some cases, this meant pulling down brick walls, saving original hardware and jail doors, and rebuilding walls using QUIKRETE Mason Mix Type N. The former jail was transformed through meticulous planning into 18 suites and a variety of public spaces, including a lobby and reception areas, two restaurants, a bar, a grand ballroom and meeting rooms.
The transformation of the site into a luxury hotel was the work of the architect collaborating with historians, conservationists and masonry restoration experts to ensure that the end result was a careful balance between preservation and modern functionality. To restore the historical landmark, PBS Construction salvaged existing granite and incorporated it into exterior landscaping and the connection between the new and old buildings. Because the 16-story tower was composed of brick and not granite, like the former jail, a smooth transition between structures was created using re-fabricated granite sized to align with the brick on the new building. This resulted in a clean, level line where the buildings meet.
The masonry work was at the heart of the five-year renovation. More than 350,000 bricks were laid with 100, 80-pound bags of QUIKRETE Mason Mix Type N and 280 bulk bags (3,000 pounds each) of QUIKRETE Type N Aspen Tan mortar. More than 20 masons completed the brick and stone work during an 18-month span, using a total of 848,000-pounds of QUIKRETE materials.
“The QUIKRETE Companies prides itself on being a resource for renovation and restoration projects, including work on the Martin House Complex by Frank Lloyd Wright in Buffalo, N.Y., and Boston’s own Fenway Park,” says Dennis Winchester, QUIKRETE executive VP. “We were privileged to be part of this most recent project to preserve the great architectural history of Boston.”
Work crews made extensive efforts to preserve existing brick, which was eventually used to rebuild the Scampo restaurant, Italian for “escape,” and Alibi lounge, formerly the “drunk tank.” Portions of this project phase, in particular, were tedious. For example, to make doorways bigger, crews had to remove entire walls, which made the structure shift. All the while, workers took care to preserve old hardware and original wrought-iron bars, now adorning the three-story arched lounge and lobby windows. Among the other features preserved were remnants of jail cells within the hotel lobby bar and the historic catwalks that wrap around the central atrium.
One of the challenges faced during the project was the Massachusetts climate, because a majority of the work was done during the winter months. In order to keep mortar from freezing, masons were careful to keep temperatures above 40 degrees using enclosed scaffolding and running heaters 24 hours a day.
In addition to this challenge, the building was close to the street, making the mixing site extremely tight. This increased the importance of logistics and inventory management. Since the area designated for mixing was confined to a small alleyway, the QUIKRETE bulk mortar and Spec-Mix silo system proved to be an invaluable resource to masonry crews.
“We wanted to work with The QUIKRETE Companies, because the Spec-Mix silo system accommodated our limited work space and helped save labor costs without need for shoveling sand piles,” says Joe Goncalves, general field superintendent at PBS Construction. “By using QUIKRETE bulk bags, we were able to keep the color consistent throughout the whole project. To top it off, QUIKRETE offers a variety of colors, so we had no trouble matching the original mortar to preserve the historical aspects of the building.”
Built in 1851, the original granite edifice of the Charles Street Jail was innovative for its day, comprising a cruciform-shaped structure complete with a 90-foot central rotunda and cupola. The jail was originally designed to house one inmate per cell, but was forced to double up occupancy. As the physical conditions grew worse, with peeling paint, outdated plumbing and increasingly overcrowded cells, the jail was forced to close in 1990. Before closing, the prison hosted many famous inmates, such as former Boston Mayor James Michael Curley, who served time for fraud after he took a civil service exam for a friend in 1904. Since opening in September 2007, the hotel has welcomed many notable dignitaries and celebrities from around the world as guests. Additional information on the project and Liberty Hotel can be found at www.LibertyHotel.com.
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|Last Updated on Friday, 01 May 2009 09:43|