Although you often have to look for it, there usually is a rich history in the shadows of the high rises and conspicuous edifices that have become the modern American city. St. Paul is no exception. Start out at the behemoth that is the Xcel Energy Center and walk west down Exchange Street and you come across the Victorian home of Alexander Ramsey, the first territorial governor of Minnesota. Continue down this path and you will be treated to similar architectural time pieces until you come across something that again seems out of place, but as it turns out, no less historically significant to its Victorian neighbors. Little Sisters of the Poor has been a mainstay in St. Paul as a home for the elderly poor for 123 years.
It all started in France, due to the charity of their founder Jeanne Jugan, who is credited with the care of a poor blind woman in 1793. That act of kindness inspired some 307 senior homes throughout the world. In this context the mission of Little Sisters is clear, they take in the aged who have no other place to go. They also take a vow of hospitality to the people to whom they administer their care.
Assessing the ProblemIt was in August of 2004 that architect Burnell Olson, of Adkins Association Architects Inc., asked the Bureau to meet at the St. Paul Little Sisters House, to discuss some of the more obvious issues afflicting the exterior wall facade of this structure that was built in 1976. The wall system can be classified as a Minnewall installation, which was marketed by the Minnesota Lath and Plaster Bureau at the time. According to the specification contained in Bureau files, this consisted of 18-gauge metal studs, over which, 1.5 inches of Styrofoam TG (tongue & groove) insulation was installed. Interestingly enough, the Styrofoam was considered to be a rigid enough base in lieu of any type of sheathing for the stucco installation. One layer of #15 asphalt-saturated felt was then applied over the Styrofoam.
Lathing components consisted of #3.4 galvanized self-furring lath, corner aids at exterior corners, zinc control joints for all the first-floor joints and back-to-back casing beads for all joints above the first floor. These were spaced 1/4 inch apart for a subsequent caulk joint. The portland cement plaster skin consisted of conventional materials in the composition of the scratch and brown coat, with a 1/8-inch manufactured cementitious finish coat. A note dated May 3, 1976, corroborates “Exterior wall system to be installed per drawings and specifications.” Coincidentally, no loose fill insulation was used between the metal studs and no vapor retarder was installed between the drywall and the framing. Add that no sheathing was used, and it might be easy to dismiss these anomalies from traditional building practice as a physics experiment gone awry. The fact is that these omissions were calculated and probably contributed to the survival of the building from mold issues over the years.
1980 - 1982Archived files maintained at the Bureau confirm a long litany of water infiltration issues that date back to when the building was first occupied. The contractor to the project noted “the leaks have usually appeared on the ceilings of the first floor, immediately below the exterior stucco walls of the tower ... We have gone to all kinds of trouble and expense to try to find the cause of this leakage. After it rains, they have buckets to catch water.” A testing company hired in the summer of 1980 concluded that water leaks in the lower floors of the building could be entirely sourced to large cracks (5/32-inch) in the stucco. Interestingly enough, the testing company provided this information after minimally testing the efficacy of the windows and concluding that they were not leaking. In their recommendations “the casing beads, which are continuous through the wall, contribute to the cracks due to thermal movement of the wall ... Further evaluation should be performed by the designing engineer to ensure the expansion joints are adequate for the amount of thermal movement encountered in the building.” According to their calculations the expansion and contraction of the stucco panels was approximately .7-inch per 100 feet of length. The logical implication was that the joints were not wide enough and there were not enough of them.
By September 1980, the preponderance of evidence escalated into aggressive correspondence between the parties involved in the construction of the building. Other observations offered were that the stucco was not properly moist cured, that the lath ran continuously through the control and expansion joints, and that the #15 felt lapped over the flanges of casing beads used to form the expansion joints instead of continuously behind them. All of these issues were contested by the stucco contractor, who noted that “to the best of their knowledge the panels were moist cured and that the inspections and reports revealed contradictory conclusions on whether the lath was indeed continuous or broken at the joints.” A final note by the stucco contractor was made that their position “is (was) that it never was the intent of the #15 felt paper punctured by numerous screw holes to be the waterproofing membrane for the building. Rather, the #15 felt was used to protect the Styrofoam from yellowing due to direct sunlight prior to the stucco application.”
Nearly one and a half years passed before the realization that more was afoot with the building than just stucco issues. In the spring of 1982 the testing company came back with yet another report that concluded that “The water infiltration problems at this structure were caused by more than one factor in the construction.” Joining the stucco as suspect causes were the “built-up roof membrane, caulking for stucco joints and poor window factory fabrication.” Gone was the adamance that the stucco itself was the stand-alone issue. The new report even seemed to acquiesce, in that the ... “water infiltration has caused damage to the exterior stucco panels,” rather than the other way around.
Water intrusion issues resulted in a new PVC membrane being added over the existing roof. Window joinery was sealed and interior repairs included replacing water-damaged ceiling tiles, and in some areas, 18-24 inches of drywall at the bottom outside walls of many of the rooms. It was also at this time that the decision was made by the testing company to “cut out all the stucco vertical and horizontal joint intersections, removing the caulking and back-up rod stock material.” As noted, this involved “carefully cutting out the stucco edge beads to complete the separation.” The testing company also urged, “If the waterproof membrane (15-pound felt) becomes cut or in areas where it is not encountered, apply an approved sealant material to the back of the joint space with a long nose gun.” This action, it turned out, was easier said than done.
Fast Forward to 1997By 1997 Maintenance Supervisor Larry Andrews realized that serious issues with both the roof and the existing windows continued long past those original repairs. “There were three successive roof failures,” noted Andrews. “The first was the failure of the original concrete pour, the second was the PVC cladding installed over the concrete, and the third was a failure of the seams of an EPDM covering.” In consultation with architect Burnell Olson, Principal of Adkins Association Architects, it was decided that something needed to be done to alleviate the continuing roof problems. “We decided that the roof needed to be stripped to its bones and reconstructed,” noted Andrews. “The roof we have on the building today was reconstructed in 1997.”
With that headache fixed, problems with the original windows used on the project began to be revealed. The same manufacturer of the original windows stepped in with new replacement windows that they claimed would not leak. “That lasted about two years after they were installed,” Andrews said.
2004“The testing company we hired in 2004 brought in spray racks and tested about seven windows, but none of them seemed to even leak a trickle,” noted Andrews. “That’s when I made the suggestion that maybe they should turn off their vacuum. The water began to just pour in,” Andrews proclaimed. Apparently the negative vacuum was just enough to cause suction between the sash and the frame of the windows.
Architect Burnell Olson took special care in researching the type of windows necessary for replacement. “What is not readily apparent,” said Olson, “is that the building is not only eight stories tall, but it sits on top of a cliff high above the river. That makes our eight-story building essentially a 15-story building. The new windows were considered because they met the wind load requirements of a much taller building.”
When asked whether the stucco contributed to the water problems on the building, Adkins Association was unequivocal in responding yes, but they also corroborated the position of Larry Andrews on the state of the building before the repairs. “Look at this stuff,” exclaimed Mike Ostlie of Adkins Association Architects. “This was taken near the top of the building,” he said, displaying a piece of stucco approximately 1.5 inches thick. Apparently, as the construction of the eight floors of the building progressed, it increasingly became more slightly out of plumb. This was made up for in the thickness of the stucco. Ostlie went on to note that the repair of the expansion joints in 1982 did more to the building’s detriment than it helped. In cutting out the existing expansion joints the #15 felt was breached and over time the joints failed. This not only contributed to moisture infiltrating the wall, but it also caused the lath and their attachments to the framing to rust and become suspect.
Even with all of the moisture problems associated with the building over the years it seems divine intervention allowed it to hold up as well as it did for 30 years. Water that had gotten into the wall assembly had not created any significant mold issues and the metal framing that made up the curtain wall did not rust. “Water would simply find its way to the bottom,” said Andrews. The fact that there was no interior vapor retarder or interior batt insulation was perhaps the saving grace in a calamity of problems with the construction of the building. Possibly due to a robust air exchanger, the building dried out effectively between rain events.
2006“I thought the stucco looked pretty good,” noted recladding project foreman Rich Willox of Mulcahy Inc. “Aside from a little cracking here and there, I thought we could have put the EIFS directly over the stucco,” he acknowledged. “I thought it was a little like removing cement block,” added Jake Boerboon, Project Manager for General Contractor Kraus Anderson. As per typical operating methods on plastering deconstruction, the stucco was first cut into smaller, easier to remove panels with circular saws equipped with diamond tipped blades. “The building was then canvassed into twenty-four segments or drops,” noted Boerboon.
Reconstruction began with the installation of Densglass Gold sheathing that would subsequently be covered with Senergy’s trowel-applied Senershield water-resistive membrane coating. “This is a Cadillac,” offered Willox. “No water is going to go through this stuff,” he added. Given that there were no balconies or unusual details other than the windows, the reconstruction settled into ensuring the same quality standards in a repeating pattern. The hardest part seemed to be the integration of the window flashing to the Senershield membrane. “Nine times out of 10 we had to replace some part of the wood buck that held the window in place,” noted Boerboon. Rotted wood, mostly at the sills, was replaced with pressure treated materials.
What made this point interesting was the configuration of the EIFS in lieu of the stucco that it replaced. Three inches of EPS supplanted the thermal shortfall in changing from the original extruded polystyrene insulation value. This had its good and bad attributes with respect to the flashing of the window installation with the new trowel-applied membrane and EIFS. The original wood bucks used to frame the rough opening were set proud to originally accommodate the Styrofoam and stucco. This now made a rather awkward step around the opening that had to be accommodated by the flashing membrane and the added thickness of insulation.
The flashing issue was addressed by wrapping a polyester-faced, adhesive-backed membrane called Senerflash over the rough wood bucks and onto the plane of the sheathing. The Senershield water-resistive membrane was then trowel-applied over the polyester face of the Senerflash, effectively integrating the window flashing directly to the water-resistive barrier. Drainage for the EIFS system was effected by adhering the insulation board with vertically oriented beads of adhesive.
The other tricky part to the whole execution of this detail was the thickness of the insulation board in relation to the step configuration created by the window buck. “We had to notch the foam board all the way around the opening,” explained Willox. “Each ‘L’ shaped piece of insulation board at each corner had to be back cut to conform with the rough buck that framed the opening,” he added. Additionally, the head, jamb and sill all had a different return configuration. All of these pieces were then pre-coated with base coat and reinforcing mesh in the shop, then integrated to one another with mating middle pieces of similar configuration on the jobsite. A rather daunting task you might conclude considering there were over 215 new windows installed on the project. “It went like clockwork,” noted Brian Mulcahy, Vice President of Mulcahy Inc. “Making a mock-up in the shop helped considerably,” he added. “That helped iron out a systematic approach that was followed on every window.” As it turned out, the approach to these issues also had its advantages. By notching out the back of the foam board, a concealed sealant joint was created. “We felt that the design actually aided in protecting the sealant joint,” responded Olson. “Sealant joints are typically a maintenance item, so whatever can be done to minimize that exposure of the joint to the elements must be considered a plus.”