During the course of my career, I have on many occasions worked on projects of historic significance, where historic preservation boards governed any proposed work, particularly work affecting exteriors. In my experience, such boards have at times insisted on absolutely unwavering adherence to the original design, even when that original design—wonderful and beloved though it may be—makes serious technical errors, which plague the buildings and their occupants and owners.Therefore, it is my contention that buildings of historic significance are best preserved by using judgment to maintain or duplicate the building’s original appearance while taking the opportunity to enhance performance and correct technical errors. We already upgrade historic buildings structurally to enhance the survivability of their occupants and the buildings themselves in earthquakes, as well as retrofit insulation to enhance energy efficiency. Correcting technical errors and enhancing a historic building’s enclosure performance, particularly where such enhancements can be largely concealed and not visually distract from the original design, makes overwhelming sense in my opinion.
I have been involved with the re-cladding and seismic upgrade of the Alaska State Capitol, Juneau, for 11 years. Alaska has no historic preservation boards with which to contend. Therefore, the capitol project, which is scheduled for completion at the end of the 2016 construction season, illustrates “rational historic preservation” of notable buildings.
The Alaska State Capitol was designed as the Federal Territorial Building in 1929 and completed in 1931, just as the Great Depression was in its infancy. It consists of a concrete frame structure with some riveted steel girders at the house chambers and multi-wythe masonry infill walls, which include brick, limestone, granite, marble and colorful terra-cotta elements.
My involvement with the building began in 2006 when I was asked to take a brief look at its exterior masonry and provide a verbal summary. This examination unexpectedly revealed severe masonry degradation and cracking, relatively widespread leakage to the interior, spalling of the stone cladding from anchor corrosion, among many other symptoms. The brick appeared as if it had been sandblasted and contained various cracks, some extending more than 10 feet. In short, the building’s exterior masonry was in rather poor condition, particularly in view of the building’s relatively young age.
Further, the stone entry portico appeared to suffer severe water infiltration and associated damage, as well as seemingly dangerous cracking of stone beams supporting the portico’s roof.
These issues were brought forth in my summary, which recommended the portico, in particular, be more closely evaluated because of its seemingly dangerous cracking and degradation.
My next opportunity to see the building came in 2010 when I was asked to take a much closer look at the portico and provide a report for it. This inspection confirmed my earlier concerns.
Although the focus of my second investigation was the portico, this element was so inte- grally intertwined with the building’s exterior wall that analyzing the problems plaguing the portico unavoidably required analyzing the full height of the building’s exterior wall above the portico. Because much of the entire building is built identically, my portico-focused investigation ended up analyzing much of the building’s exterior by default.
For example, the severe leakage plaguing the portico ceiling did not originate with its roof, but rather resulted from the downward migration of moisture within the building’s multi-wythe exterior masonry walls above, which—reflecting construction methods of the time—did not incorporate through-wall flashings or weeps to capture and drain water out of inherently absorbent masonry. Instead, the builders attempted to rely on the masonry thickness and mass to limit infiltration to the interior. While this “mass masonry” approach may suffice for many exterior detailing conditions in much drier climates, it has little chance against Juneau’s 220 days of precipitation annually.
In short, my closer look revealed the portico had suffered seismic damage in the past and appeared very vulnerable to potentially severe damage in any future earthquake. It obviously had been plagued by severe infiltration for 80 years, compromising the integrity of its stone ceiling panels and possibly its concrete roof structure through corrosion of its reinforcing, embedded steel tie-straps and steel beams. Further, the entire building appeared vulnerable to severe damage during future earthquakes. In addition, by virtue of the absence of through-wall flashings and drainage provisions within its exterior walls, infiltration to the interior and damage to interior finishes, as well as to the masonry, would continue to plague various parts of its exterior walls.
PHOTOS: PAUL LUKES: Building Envelope Consulting Services LLC
In view of the already extant damage to its masonry, my report cautioned that seemingly random shedding of fist-sized masonry chunks off the building’s facades should be expected.
About two years later, a senator’s aide was entering the building for work when a fist-sized chunk of masonry came crashing down 80 feet and shattered next to him. This crystallized the potential risks of inaction, leading to my third visit to the building at which time I was asked to assemble a team of experts to evaluate the building in its entirety and develop corrective options. The team included architect Wayne Jensen of Juneau-based Jensen Yorba Lott Inc. Greg Coons and Paul Faget of the Seattle-based structural engineering firm Swenson Say Faget formed an integral part of the team by virtue of their recent design of similar structural retrofitting at the Washington State Capitol.
All examined the building and its detailed design from their disciplines’ perspectives over several days to begin developing appropriate corrective options addressing the building’s multi-layered problems. This afforded the opportunity to examine portions of the building’s exterior I had not previously accessed, revealing more of the degradation symptoms expected, namely serious weathering of its masonry.
For example, starting at the building’s top, the roof-level masonry band that replaced the original cornice was spalling extensively, in particular along a projecting narrow band, posing appreciable risk to pedestrians below.
In short, the Alaska State Capitol, perhaps the state’s historically and architecturally most significant building—one more than worthy of preservation—was in quite poor condition with many of its exterior masonry elements very near, in many cases beyond, their safe, usable lifespans. The capitol was posing life-safety risks to pedestrians below its walls because of the extant damage to its masonry; experiencing interior leakage in many locations; and its very structure was vulnerable to complete seismic collapse, thus risking the state’s effective decapitation just when the government’s resources would be most critically needed following a significant earthquake.
The “expected” pathway for addressing the host of issues plaguing this venerable building—the pathway which based on my prior experience would have been absolutely mandated by any overseeing historic preservation boards—would be to do all possible to preserve all existing masonry while addressing the structural and other deficiencies.
Yet, it was clear given the full constellation of problems plaguing this structure, this would involve a massively costly effort while still yielding at best marginal results. Plus, it would only extend this building’s day of reckoning by 40 years at most. This approach would require removal of all hollow clay tile lining the inner faces of all exterior walls to allow new concrete shear walls to be shotcreted against the existing masonry to provide the structurally needed shear walls. It would require costly retrofitting of through-wall flashings to preclude infiltration into the portico ceiling and below many windows. It would similarly require all existing masonry be anchored to the new concrete shear walls with tens of thousands of steel pins. The masonry would need to be patched with suitable repair mortars and treated with consolidating agents to help stabilize its degraded integrity, which even under the best circumstances would have bought 40 years before another round of very costly repairs would be needed.
In this approach, the overall building would become heavier by replacing thin hollow clay tile with thick concrete shear walls, thus exacerbating seismic stresses and requiring addition of yet beefier foundations and shear walls. The exterior masonry would still continue to erode away and drop chunks onto sidewalks be- low, though hopefully with less frequency for some years. Further, this approach allowed no significant enhancement of the building’s energy efficiency, leaving its exterior walls largely uninsulated with total R-values ranging between R-3 and R-4, depending on location. Although insulation could in theory be added inward of the new shotcrete walls, this would not only reduce already tight interior space, but posed a risk of accelerating further degradation of the masonry and was thus inadvisable. Our team proposed this option—“Maximum Preservation”—with a cost of roughly $18 million.
This approach made no sense, so I suggested another approach be considered: complete reconstruction of the building’s exterior to match as closely as possible the original design while taking advantage of the opportunity to technically enhance the cladding’s performance and correct the technical flaws inherent in the existing design. Although this seemingly radical suggestion at first met with understandable hesitation, the potential advantages of this approach afforded compelling arguments.
This approach would ironically simplify the work: All exterior walls would be re- moved to allow easy access for installing new concrete shear walls, which would then remain fully accessible to allow new masonry to be anchored to them. It would lighten the building, replacing in many locations 16 inches of masonry with 8 to 12 inches of concrete and brick, thus further reducing seismic risk and the amount of new concrete shear walls. It would provide a new masonry cladding closely resembling the original but with a plausible lifespan of 100 to 150 years even in Juneau’s masonry-challenging climate. It would also allow major enhancement of energy efficiency, increasing the exterior walls’ insulating value to roughly R-20 in some locations and more than R-40 in many other areas. This approach would also allow easy correction of the original design’s technical flaws, by installing suit- able flashings atop all ledgers and lintels, below window sills, and at similar suitable locations to drain water back out of the cladding; to cap over ill-advised, skyward-facing masonry surfaces with historically compatible copper flashings; and make similar enhancements with very limited visual impact. This option—“New Masonry Veneer with Concrete Walls” —would cost roughly $22 million.
With either approach, I strongly recommended the original roof-level cornice be reconstructed of precast concrete; this would not only restore the building closer to its original appearance, but would appreciably help protect the new masonry from weathering, helping extend its lifespan.
Recognizing the powerful advantages of the “New Masonry Veneer with Concrete Walls” option, the state of Alaska accepted this recommendation.
PHOTOS: PAUL LUKES: Building Envelope Consulting Services LLC
Corrective Design and Construction
Given the Phase 3 team’s expertise and deep familiarity with the Alaska State Capitol’s extensive problems, the same team was selected to carry forth the corrective design.Because of the potential life-safety risks posed by the seriously damaged portico, corrective design was actually divided into two sub-phases, the first of which pertained to the reconstruction of the portico structure while the second described work at the remainder of the building. This allowed the most critically needed corrective construction at the portico to proceed in 2013 while the design for the following years’ corrective work continued.
Corrective work at the portico began with removal of all portions of its structure, except for its four marble columns, which were core-drilled through their entire height to allow reinforcing strands to be grouted through these to tie the separate marble sections together and to the foundations. A new concrete-frame structure of beams, pilasters and a roof slab was cast atop these columns with a temporary EPDM roof over this to protect the structure until the following year when this skeleton was clad with precast concrete cladding to match the existing, severely damaged stone.
In brief, corrective work at the rest of the building, executed during 2014-16, consisted
of complete removal of all exterior masonry to fully expose the building’s concrete skeleton; installation of new shotcrete shear walls for seismic enhancement; and over-cladding the structure with a new masonry cladding to closely resemble the original building while also incorporating many technical enhancements, including insulating the building with rigid insulation outside the concrete structure and adding interior insulation for maximum energy efficiency. Because the existing brick face was 9 inches outside the concrete structure in many locations, this allowed addition of 4 1/2 inches of rigid insulation. Elsewhere, where the masonry fell closer to the concrete skeleton, lesser amounts of insulation could be placed within the masonry cavities, where added interior insulation was of greater consequence. Depending on location, the new exterior walls had insulating values ranging from about R-20 to more than R-40.
The original terra-cotta roof-level cornice band, removed decades ago because of its degradation (which reflects its inadequate design), was replicated using precast concrete. To preclude infiltration and protect its integrity, the cornice was capped with EPDM membrane, a thin vent mat and standing- seam copper roof.
To allow the masonry to dry out as rapidly as possible following each rain, the masonry design incorporated weeps, which allow air to enter behind the cladding, at panel bot- toms. Outward-sloping panel-top vents were installed to exhaust air out from behind the cladding, thus setting up a thermosiphon drying effect.
In summary, this venerable capitol had been designed as many of its contemporary peers, which proved woefully inadequate for Juneau’s very masonry-challenging climate. Consequently, its exterior elements displayed a level of degradation far beyond the building’s relatively young age. Further, the building’s overall structure was not designed to perform adequately in earthquakes of plausible magnitudes, had suffered seismic damage to various exterior masonry elements and was at risk of complete collapse when the inevitable significant earthquake takes place.
This building’s many serious issues could have been addressed in the expected fashion, namely by exerting all effort to maintain its exterior masonry elements and installing interior shotcrete shear walls to enhance seismic performance. Based on past experience, I am very confident that this restoration pathway would have been mandated by many historic preservation boards.
Yet, this “preservation” approach would have proved very costly; produced a building whose exterior masonry would still continue to crumble away onto pedestrians below; continued to consume inordinate amounts of heating energy each year; made the building yet heavier, thus requiring additional seismic upgrading to address the increased movement stresses; and reduced already tight interior space by thickening the exterior walls inward. Further, this approach would at best have extended the lifespan of the building’s exterior by perhaps 40 years, at which point further attempts to preserve the existing masonry would have proved futile, requiring very costly replacement in just a few decades.
In contrast, the “reconstruction” approach actually allowed the building to become lighter and seismically safer; made the exterior walls much more energy-efficient, reducing heat loss through the masonry by roughly 90 percent; and gave the building a new lease on life, probably extending the lifespan of its exterior cladding 100 to 150 years. It allowed the building to regain its originally designed appearance while accommodating barely perceptible corrections of its technical errors. In short, the “reconstruction” approach vastly improved the building’s seismic performance and safety, greatly extended its lifespan and improved its energy efficiency immensely at only marginally higher initial cost than the largely futile “restoration” approach would have cost.
Client: State of Alaska, Legislative Affairs Agency, Juneau
Architect: Jensen Yorba Lott Inc., Juneau
Structural Engineer: Swenson Say Faget Inc., Seattle
Building Envelope Consultant: PAUL LUKES: Building Envelope Consulting Services LLC, Seattle
Electrical Engineer: Haight & Associates Inc., Juneau
Mechanical Engineer: Murray & Associates P.C., Juneau
General Contractor, Portico: Alaska Commercial Contractors, Juneau
General Contactor, Building: Dawson Construction Inc., Juneau
PHOTOS: PAUL LUKES: Building Envelope Consulting Services LLC
Download a PDF (click on the image to the left) for a more in-depth report—along with photographs and illustrations—about the Alaska state Capitol’s problems and solutions. Author Paul Lukes also touches upon related technical subjects, including how buildings get wet and how this affects building envelope configuration.