THE PERFECT STORM: RESTORATION OF THE MEMORIAL HERMANN HOSPITAL TEXAS MEDICAL CENTER AFTER HURRICANE IKE

Transcription

1 THE PERFECT STORM: RESTORATION OF THE MEMORIAL HERMANN HOSPITAL TEXAS MEDICAL CENTER AFTER HURRICANE IKE AMY PEEVEY, PE, RRO, CDT BUILDING EXTERIOR SOLUTIONS, LLC 6975 Portwest Drive, Suite 100, Houston, TX Phone: Fax: T H R C I I N T E R N AT I O N A L C O N V E N T I O N AND TRADE SHOW MARCH 15 20, 2012 PEEVEY 81

2 ABSTRACT The Memorial Hermann Texas Medical Center is a certified level-one trauma hospital essential for providing emergency care for Houston. On September 13, 2008, Hurricane Ike struck the Houston area. The Center s signature clay roof tiles were damaged and became airborne, impacting the underlying buildings. Exterior glazing and roofing system damage was sustained throughout the Center. Building Exterior Solutions, LLC, (BES) was retained as the engineer-of-record to evaluate, make repair recommendations, develop associated repair documents, and perform construction observations for the Center restoration. As a part of the restoration design, BES s major concern was allowing the hospital to remain in operation with little to no occupant and patient disruption. In addition, BES strived to retain the existing Center s aesthetics while providing effective repair solutions that would prevent future occurrences of global failure, as well as provide long-term repair and/or replacement solutions. SPEAKER AMY PEEVEY, PE, RRO, CDT BUILDING EXTERIOR SOLUTIONS, LLC HOUSTON, TX Throughout her career, AMY PEEVEY has participated in a wide variety of projects for the investigation, evaluation, repair, and construction of structural, architectural, and material-related building problems. Her experience includes the investigation, evaluation, analysis, repair design, and construction monitoring/administration of building envelope and building structural problems. Ms. Peevey specializes in design peer review; building envelope commissioning; and failure investigation, evaluation, repair design, and construction monitoring of building envelope systems. She is an active member of several professional societies and has published in an ASTM International special technical publication on inspection of natural stone façades. 8 2 P E E V E Y 2 7 T H R C I I N T E R N A T I O N A L C O N V E N T I O N A N D T R A D E S H O W M A R C H ,

3 THE PERFECT STORM: RESTORATION OF THE MEMORIAL HERMANN HOSPITAL TEXAS MEDICAL CENTER AFTER HURRICANE IKE The perfect storm occurs when a number of rare factors come together to create an extraordinarily negative outcome. On September 13, 2008, when Hurricane Ike struck the Galveston, TX, coastline approximately 50 miles south of the Texas Medical Center as a Category 2 hurricane, the main campus of the Memorial Hermann Hospital felt that was the case for this storm. The hurricaneforce winds caused portions of or whole clay roof tiles to disengage from several buildings of the campus s steepslope roofing systems. The resulting damage was due to a domino effect. The damaged clay tile roof systems (Figures 1A and 1B) resulted in wind-borne debris that impacted the exterior wall and roof systems of the underlying buildings throughout the campus. Damage to the exterior wall cladding, glazing, skylights, and roofs was sustained (Figures 2A and 2B), resulting in water infiltration. Additionally, a portion of the newly installed Heart and Vascular Institute roof system delaminated, resulting in failure of the single-ply roof membrane (Figure 3) and subsequent water infiltration into the building. The widespread damage throughout the campus appeared overwhelming. However, the Memorial Hermann Hospital System personnel quickly assembled a team of professionals to assess and remediate the damaged campus. The result was an effective and efficient restoration of the Memorial Hermann Texas Medical Center Campus. The following presents the manner in which the project team developed the project objectives, approach, and design to make the restoration a success. Figure 1A Disengaged and broken clay tile at Jones Pavilion. Figure 1B Missing and disengaged clay tile at Cullen Pavilion. Figure 2B Broken glass units of Hermann Pavilion monumental skylight system. Figure 2A Broken glass units of Hermann Pavilion curtain wall system. 2 7 T H R C I I N T E R N A T I O N A L C O N V E N T I O N A N D T R A D E S H O W M A R C H , P E E V E Y 8 3

4 were determined or modified as necessary to meet the project requirements. In addition, the project team made sure that the FEMA documentation and requirements were satisfied. Figure 3 Broken glass units of Hermann Pavilion monumental skylight system. Arrow denotes HVI roof failure area. THE CAMPUS The Memorial Hermann Hospital Texas Medical Center campus is located in the northern portion of the Houston medical center (Figure 3). This level-one trauma center provides essential emergency and medical care to the Houston area. The campus is comprised of five major sections that were constructed between the 1920s and These sections are the Cullen Pavilion, Robertson Pavilion, Jones Pavilion, Hermann Pavilion, and the Heart and Vascular Institute. The buildings within these sections range in height from a single story to 13 stories. Overall, the campus contains over 200 low-slope and steep-slope roof areas that are constructed of built-up, modified-bitumen, single-ply, and clay tile roof systems. Additionally, several of the buildings contain aluminum-framed glass skylights. The campus s exterior cladding systems generally consist of a combination of precast concrete or limestone panels, stucco, and brick masonry façades with aluminum-framed glass curtain walls and wood-framed or aluminum-framed punched window openings. The Project Team Prior to the arrival of Hurricane Ike, Memorial Hermann Hospital System assembled a team to be ready in the event that damage was sustained. Many team members were on site during and immediately following the storm to begin the evaluation and repairs from the hurricane damage. The key project team members were the Memorial Hermann Hospital System as owner, project manager, and building engineer; Manhattan Construction as the general contractor; Curry Boudreaux Architects as the project architect; and Building Exterior Solutions, LLC (BES) as the building envelope consultant. BES s responsibilities were to evaluate the posthurricane conditions, assist with the scope development and prioritization of repairs, design the associated repairs and/or replacements, and perform construction observations for the campus restoration. The project team developed an overall restoration plan that required collaboration from each of the team members so that the hospital s requirements could be met. Initially, the owner s requirements and corresponding project objectives were established. Then the approach for the fulfillment of each of these objectives was developed. As a result, the project team prioritized and divided the restoration scope so that the restoration repairs could begin at critical areas while evaluations and designs for other portions of the restoration work were being developed. As a part of the project team collaboration, weekly meetings were conducted to review key project elements such as schedule, budget, safety, sequencing, access, etc. During these meetings, the current restoration work, the analysis from current evaluations, and the design for previously evaluated systems were reviewed, and the scopes THE OBJECTIVE As a part of the campus s restoration design, the most critical objective was to allow the hospital to remain in operation with little to no disruption to hospital personnel or patients. In addition, the project team strove to retain the existing campus aesthetics while providing cost-effective repair solutions that would avoid future occurrences of global failure, as well as providing long-term repair and/or replacement solutions. Special considerations for the project included asbestos-containing materials, salvaging clay roof tile and architectural stone elements, constructability on steep-slope roofing systems, internal roof drainage systems, historic structures, design and coordination with Life Flight helicopter operations, construction impact on other building systems, accessibility of areas that were to undergo repairs, and maintaining the safety of hospital occupants while providing cost-effective, longterm repair and replacement solutions. THE APPROACH To achieve the project s objectives, the team divided the rehabilitation scope into two phases: Phase 1 initial assessment and temporary repair phase; and Phase 2 comprehensive evaluation and long-term repairs. Dividing the rehabilitation into immediate versus long-term repairs enabled the buildings to initially be dried while the long-term comprehensive repairs were developed. Phase 1 Immediate Repairs Immediately following the storm, the hospital staff, general contractor, and subcontractors began repairs on the most significantly impacted areas. Meanwhile, the project team s most critical priority was assessing the damage and initiating temporary repairs to ensure the buildings were dry. In order to develop the planning necessary for these temporary repairs, a full survey of the campus was conducted to determine locations of damage that were at risk for water infiltration. As a part of this assessment survey, aerial photographs were taken of the campus in the days following the storm (Figure 3). These pho- 8 4 P E E V E Y 2 7 T H R C I I N T E R N A T I O N A L C O N V E N T I O N A N D T R A D E S H O W M A R C H ,

5 Figure 4 Removal of broken glass units and installation of plywood for temporary protection at Hermann Pavilion. Figure 5 Rope access for removal of broken and disengaged clay tiles. tographs assisted the team with identifying the most heavily impacted areas and with the assessment of areas that were not easily accessible. With this information, the project team was able to prioritize the immediate repairs. Corresponding temporary repair designs were developed in order of priority to address the existing damaged conditions. These designs included the installation of temporary coverings, removal of glass and installation of plywood at window openings, installation of concrete curbs within the penthouses to prevent water infiltration to lower floors, securement of damaged operable windows, and other necessary measures. These temporary repair packages were issued individually as dictated by project need so that the buildings were quickly dried, and corresponding interior repairs could be performed. As the temporary repairs were conducted, the project team assessed the damage to evaluate the need for precautionary measures to address potential unsafe conditions. In order to develop the scope for these measures, a binocular survey was performed of the entire campus to identify potential fall hazards of the exterior wall and roof system components. The survey documented and logged all identified potentially unsafe conditions that posed a threat to the hospital occupants and underlying areas. From the survey results, plans and elevations of potential unsafe conditions and associated protocols for how each condition should be remediated were provided. The remedial measures were then put into place, which included stabilization of components, temporary protection such as the installation of netting or overhead protection, and removal of potential fall hazards. Specifically, the damaged large monumental skylights of the Hermann Pavilion (Figure 2B) were initially cordoned off. Safety netting and overhead protection were later installed to protect building occupants. In addition, the broken glass units and disengaged clay tiles were removed by hand (Figures 4 and 5), and overhead protection was provided at some building entrances and other locations as required. Phase 2 Comprehensive, Long-Term Repairs Once the buildings were dry and the campus was protected from potential hazards, a comprehensive evaluation of the damage and long-term strategy for restoration were developed. BES initially per- formed visual field observations of each damaged roof and wall area. During these observations, each area was documented with photographs, field notes, and sketches. Then the field data were evaluated; and each area was inventoried by location, type of system, and extent of damage. With this information, the project team ranked each area by priority based on the level of distress and its importance, as well as sequencing of adjacent roof replacements. The damaged campus areas were placed into one of three priority levels: immediate, short-term, and long-term priority. This plan allowed the team to evaluate the entire campus and break up the restoration work into packages according to critical needs for hospital operations, priority level of repair, locality, and accessibility. Following the establishment of priority areas, the scopes of roof and exterior wall rehabilitation were divided into individual packages with the immediate priority areas sequenced first, the short-term priority areas next, and finally, the long-term priority areas. This portioning of the work enabled the rehabilitation to begin at the most critical areas, while simultaneously evaluating and designing repairs for others. The resulting phased approach allowed the hospital to begin restoration to reduce the risk of additional failures or damage-related problems (such as fall hazards, additional 2 7 T H R C I I N T E R N A T I O N A L C O N V E N T I O N A N D T R A D E S H O W M A R C H , P E E V E Y 8 5

6 were conducted to confirm the as-built construction of each assembly (Figure 6). At metal and lightweight concrete roof decks, field-testing was performed to determine the strength of the systems (Figure 7) so that appropriate repair designs could be developed. Finally, water testing was performed at exterior wall locations to determine the source of water infiltration for proper development of a remedial repair plan. Figure 6 Roof investigative opening (test cut). water infiltration, etc.) while allowing adequate time for proper evaluation and restoration design of systems that were lower priority. Once the restoration packages were established and as the initial immediate repairs were under way, BES designed the repairs for the next package and simultaneously conducted additional field evaluations for the design development of subsequent packages. These evaluations included field observations and testing of the existing systems to determine the scope of the repair or replacement design. Visual observations and field measurements were conducted to evaluate the condition of the systems and determine the as-built construction. In addition, investigative openings (test cuts) Figure 7 Pull testing of metal roof deck fastener. 86 PEEVEY 2 7 T H R C I I N T E R N AT I O N A L C O N V E N T I O N THE RESTORATION DESIGN At the onset of the campus restoration, general repair strategies and bases-ofdesign were developed that set precedence for the repairs. The standard for the restoration repairs and replacements was to reduce or eliminate the risk of future failures such as those that had occurred during Hurricane Ike. It was determined that replacement roof systems were to incorporate more safeguards to protect from wholesale failure, which the existing single-ply roofing systems did not provide, and to reduce the possibility for the creation of wind-borne debris as a result of roof damage. Therefore, the following strategies and corresponding bases-of-design were developed for the restoration of the low-slope roofing systems and clay tile roof systems. Low-Slope Roof Replacements The single-ply roof failure of the Heart & Vascular Institute resulted in significant impact and damage for the hospital because critical patient care was located directly below the roof failure. The resulting water infiltration affected hospital operations. Specialty patient services had to be relocated to other areas in order to provide continuity of patient care. Because a majority of each of the campus sections also provides patient care, it was determined that the roof replacement systems should provide redundancy and a means to contain failure to the damaged portions. As a result, BES proposed that the roof areas requiring replacement be replaced with a two-ply modifiedbitumen roofing system. Two-ply systems offer improved puncture resistance and are less likely to have global failures because the area of damage is limited to the portion immediately impacted. While the two-ply roofing system was slightly more costly than a single-ply system, it provided the redundancy and localization of failures that the hospital desired to reduce the risk of system-wide failures in the future. In addiand TRADE SHOW MARCH 15 20, 2012

7 Figure 8 Steep-slope roof replacement system with two-piece clay-tile roof mechanically attached and set in foam adhesive. tion, the two-ply system increased the wind-uplift rating of the roof assemblies that further limited the potential of future global failures. Steep-Sloped Roof Replacements For each of the campus s clay tile roof systems, the project team developed a twopart strategy. First, it was determined that the risk of the clay tile becoming windborne debris was unacceptable due to the widespread damage to adjacent roof and cladding systems. Therefore, the clay tile roofs were analyzed to determine which roof areas posed this threat. The analysis generally indicated that the high-rise clay tile roof areas of the main patient-care sections Cullen, Jones, and Hermann pavilions should be removed and replaced, as these systems contained mechanically fastened clay tile that resulted in damage, and each of these roofs was overlying lower roof and glazed-wall openings that contained patient-care facilities. With the scope of the clay tile roof replacements defined, the replacement roof system options were analyzed. Initially, the project team considered other types of roof cladding to replace the existing clay tile such as metal or single-ply roofing systems. Because of the potential for wind-borne debris, FEMA Design Guidelines (FEMA 577) do not recommend the use of clay tile 2 7 T H R C I I N T E R N AT I O N A L C O N V E N T I O N AND roofing systems for hospitals in hurricaneprone regions. However, as the clay tile roofs of the Memorial Hermann Texas Medical Center are the signature feature of the campus, it was determined that they should be retained. As a result, BES developed an alternative method of clay tile attachment to avoid the potential for portions or whole clay tiles from disengaging in the future, even when damaged. In addition to mechanically fastening each tile in place, which secures a small portion of the tile should it become damaged, each clay tile was also set in a full bed of low-rise foam adhesive (Figure 8). Therefore, if a clay tile were damaged, the portions that were no longer secured by the mechanical fasteners would remain in place. For the clay tile roof replacements, the original barrel-type clay tile units were to be salvaged and new clay tile ordered to replace the hurricane-damaged roof tiles or other roof tiles damaged during salvaging or construction operations. Another consideration for the clay tile roof areas was the steep slope of these areas and the ability of workmen to safely perform the roof replacement. A new self-adhered underlayment was included in the basis-ofdesign as a part of the clay tile roof replacement system. Many common self-adhered underlayments incorporate a polyethylene sheet at the exterior face. This polyethylene facing can be slick and can make it difficult for workers to maintain footing on steepslope working surfaces. As a result, BES selected self-adhered membrane products that had facings with irregular-surface profiles or that incorporated a fabric scrim facing to reduce the slickness of the exterior self-adhered membrane surface (Figure 9). Basis of Design From these general repair strategies, the Figure 9 Worker on underlayment of steep-slope mansard of Jones Pavilion. TRADE SHOW MARCH 15 20, 2012 PEEVEY 87

8 resulting in a global uplift failure of the single-ply membrane, which resulted in water infiltration into the building. Consequently, the main eighth floor roof was prioritized as the first package for restoration. The roof replacement system consisted of the standard low-slope design adhered to the concrete roof deck. In addition to the roof replacement at the eighth floor and penthouse roofs, the waterproofing of the eighth floor penthouse was incorporated into the restoration work to prevent water infiltration at the penthouse level from traveling to lower levels. These repairs included the installation of curbs at the perimeter of the penthouse floor slab and at slab openings, as well as the installation of a waterproof floor-coating system throughout the upper penthouse floor area. Figure 10 View of HVI from the northwest. following basis-of-design roof replacement systems were established. For low-slope roof systems, the new roofing system was designed in general accordance with the FEMA design guidelines (FEMA 577). However, the secondary membrane below the insulation was not provided. The design consisted of polyisocyanurate insulation set in low-rise foam adhesive; a ½-in. cover board; and a torch-applied, two-ply, SBSmodified bitumen roofing system with a reflective cap sheet. For the steep-slope clay tile roof systems, the roof replacement consisted of self-adhered membrane waterproofing over a plywood substrate, vertical stringers wrapped in self-adhered membrane waterproofing, and two-piece clay barrel roof tiles each fastened in place and set in low-rise foam adhesive. There were a variety of roof deck types throughout the campus, which are indicated for each pavilion below. Heart & Vascular Institute The Heart & Vascular Institute (HVI) is an eight-story building constructed at the northwest corner of the campus in 2008 (Figure 10). The pavilion has a concrete frame and roof deck. The original low-slope roof system at the eighth floor and lower levels was a single-ply TPO roof membrane over cover board and adhered tapered insulation. In addition, there is a clay-tile-clad roof screen at the eighth floor roof and clay88 PEEVEY tile steep-slope roofing system at the penthouse. The pavilion cladding generally consisted of precast concrete wall panels with punched windows and curtain wall. A large portion of the resulting hospital disruption and interior damage occurred to the HVI as a result of the hurricane-damaged single-ply roof failure. A portion of the roof delaminated during the hurricane, Cullen Pavilion The Cullen Pavilion (Figure 11) is the oldest pavilion of the campus with the initial portion constructed as the original hospital building in the 1920s. Two wings were added at the north and south ends in the 1960s. The pavilion construction consists of limestone panel and stucco cladding with punched window openings and steep-sloped clay tile roofs; low-sloped, single-ply EPDM; and a modified-bitumen roof. Generally, for this and the other pavilions, the upper roof areas consist of the steep-slope clay tile sys- Figure 11 Overall view of Cullen from the southwest. 2 7 T H R C I I N T E R N AT I O N A L C O N V E N T I O N AND TRADE SHOW MARCH 15 20, 2012

9 tem, and the lower roof areas are low-sloped single-ply or modified-bitumen systems. The main entry s open courtyard for the original hospital was closed in with a lowslope EPDM roof system over metal deck that incorporated new skylight systems (Figure 11). Low-Slope Roof Areas The single-story main entry EPDM lowslope roof area sustained significant damage from the debris of the overlying sixthfloor steep-sloped clay tile systems. As a result, this main entry-roof low-slope area was prioritized with the HVI main roof in the first restoration package. The existing single-ply roof system was replaced with the low-slope design system that was mechanically fastened to the metal roof deck and adhered to the concrete deck areas. The skylight system underwent replacement of the broken insulated glass unit during this phase of repairs. Clay Tile Roof Areas The Cullen Pavilion clay tile roofs consisted of a two-piece barrel clay tile system set on stringers with underlying built-up membrane over wood, steel, or concrete decks. The clay tile roof at the main entry roof and the sixth floor steep-sloped roof areas were not addressed during the lowslope roof replacement. These areas were incorporated into the restoration design in a future package. Once the potential fall hazards of these areas were remediated in the precautionary measures phase, they were placed as lower priority because they maintained a weather-tight performance despite undergoing hurricane damage. However, these roof systems posed significant issues regarding accessibility and repair design considerations. First, the steep-sloped clay tile roofs of the Cullen Pavilion were not easily accessible. Their only means of access was through openings at the penthouses that required scaling ladders and maneuvering through small openings. In addition, no provisions for fall protection were incorporated into the original roof designs due to the lack of requirements during initial construction, which spanned the decades from almost a century ago. Therefore, exterior scaffold access and roof tiebacks were installed as a part of the restoration design for access and safety during the roof repairs. In addition to access and safety issues, the Cullen Pavilion clay tile roof areas posed Figure 12 View from north of Robertson Pavilion. other concerns. As a part of each roof predesign evaluation, BES conducted visual observations to document the as-built conditions and performed field-testing to verify the condition and strength of the existing substrates. BES conducted visual observations of the underside of the roof areas to identify the existing construction and any conditions that needed to be addressed as a part of the design. During these observations, BES determined that the original 1920s hospital had a concrete roof deck and the 1960s wing additions had metal decks. In addition, the 1920s roof deck had a built-up coal tar roof system as the underlayment for the clay tile system. Due to the era of construction, the project team had the original Cullen concrete deck and overlying built-up roof system tested for hazardous materials. The testing revealed that the concrete and scrim of the built-up roofing contained asbestos. Because the Cullen Pavilion is an operating hospital with patient care at the lower levels, abatement of the concrete deck and overlying built-up roofing system was not feasible. Therefore, the project team elected to encapsulate the concrete roof deck and overlying built-up roofing as a part of the clay tile roof replacement. This approach overcame the hazardous material issue because the materials were enclosed so that they did not pose a threat to the hospital occupants. The final clay tile roof replacement design encapsulated the existing deck and built-up underlayment with a new ½-in. plywood deck that was fastened into the existing roof deck. Then the standard design steep-slope roof replacement system was installed over the new decking. Exposed interior gutters were lined with TPO membrane. The nonexposed interior gutters were lined with the self-adhered membrane and overlaid with new stainless steel gutters that incorporated bird screens to keep debris from entering the system. Robertson Pavilion The majority of the Robertson Pavilion was constructed in the 1950s (Figure 12). The pavilion comprises a series of interconnected buildings ranging from single-story to eight stories in height. The upper levels of the pavilion accommodate hospital administration, and the lower levels provide patient care. The exterior cladding is predominantly brick masonry with stone accents and punched window openings. The majority of the roof areas have low-sloped, built-up, single-ply or modified-bitumen roof systems with four clay tile steep-sloped roof areas at the eighth floor. The hurricane damage was predominantly at the low-slope roof areas. However, some of the operable windows were also damaged. The scope of the Robertson Pavilion restoration included roof repairs and roof 2 7 T H R C I I N T E R N A T I O N A L C O N V E N T I O N A N D T R A D E S H O W M A R C H , P E E V E Y 8 9

10 tems was overwhelmed by the volume of water at the hurricane pressures. As a result, water was forced to the building interior. Therefore, a repair design was developed to wet-seal the existing curtain wall and punched window openings. Wetsealing replaces those parts of the window system that deteriorate over time, such as gaskets and seals, with new sealant to extend the window system service life. These wet-seal repairs prevent bulk water from entering the window systems and, therefore, prevent the system s drainage from taking on more water than it can manage. Once the wet-seal design was developed, mock-ups and field water testing were performed to evaluate the performance of the repairs. Then the window repair work was sequenced and performed in conjunction with the other Jones Pavilion restoration scope. Figure 13 Aerial view of Jones Pavilion from the southwest. replacements, as well as securement and sealing of some of the operable windows. The low-slope roof replacements were the design system adhered to concrete roof decks, installed over vented base sheets that were mechanically fastened to the lightweight roof deck, or mechanically fastened to the metal roof decks. The window systems were permanently secured in place so that they were no longer operable and could not pose a future threat of disengagement. One of the difficult aspects of the Robertson Pavilion reroofing was providing adequate drainage for the roof replacements. In order to accomplish this task, many of the existing roof slopes were increased, resulting in elevated flashing heights that had to be coordinated with existing door and window openings. Drains, scuppers, and related gutters and downspouts were also added. Jones Pavilion The Jones Pavilion (Figure 13) was constructed in the 1960s with the addition of the eighth floor in the 1970s. The pavilion is L-shaped in plan. The exterior wall construction consists of limestone panel cladding with punched window openings and curtain wall systems. The roof systems include low-slope built-up roofs over a concrete deck at the main roof level and builtup or single-ply EPDM roofs over a metal deck at the penthouse levels. A steep-sloped clay tile roof mansard is located at the building perimeter. The Jones Pavilion roof replacements were conducted as a single package. However, the sequencing of the work had to be coordinated to prevent damage to newly installed roofing systems. Therefore, so that the low-sloped roof systems were not damaged by the clay-tile roof replacements, the upper clay tile roofs were replaced first, with the underlying low-sloped roof replacements last. Additionally, the punched windows and curtain wall also underwent repairs during the hospital restoration. Window Systems A large amount of water infiltration occurred through the Jones Pavilion window openings during Hurricane Ike. BES conducted visual observations and field water-nozzle testing to determine the source of the water infiltration. It was determined that the drainage of the existing sys- Low-Slope Roof Areas A majority of the low-slope roof systems were sequenced so that their replacement was performed after the replacement of the clay tile roof mansard. This sequencing was performed to prevent potential damage to the low-slope roofing systems from the clay tile roof replacement operations. However, the single-ply EPDM roof along the west side of the elevator penthouse was integrated with the clay tile roof mansard. As a result, this EPDM roof was one of the initial roofs replaced for the pavilion. The remaining main roof and penthouse roof areas were replaced after the completion of the clay tile roof mansard replacement. Each low-slope roof area was replaced with standard low-slope roof replacement adhered to concrete roof decks and mechanically fastened to the metal roof decks. Clay Tile Roof Areas The clay tile roof mansard sustained significant wind damage resulting in windborne debris that caused damage to the underlying window, skylight, and roofing systems. BES conducted visual observations and test cuts of the existing roof systems to determine the as-built construction so that an appropriate replacement design could be developed. The roof mansard construction consisted of metal decking with plywood sheathing and two-ply felt for the clay tile underlayment. Due to age, a large portion of the plywood decking, as well as the clay tile stringers, were deteriorated. In addition, along the eave, the mansard con- 9 0 P E E V E Y 2 7 T H R C I I N T E R N A T I O N A L C O N V E N T I O N A N D T R A D E S H O W M A R C H ,

11 tained an internal gutter system. The internal gutter system was not fully operational as a result of debris buildup within the system. The clay tile mansard replacement included new mechanically fastened plywood decking to replace the deteriorated plywood. This plywood was fastened to the existing metal roof deck as the substrate for the clay tile roofing replacement system. The drains of the gutter system were cleared, and the existing interior stainless steel gutters were replaced with new stainless steel gutters that incorporated bird screens to prevent infiltration of debris. As demolition and salvaging of the clay tile clad mansard was under way, it was determined that the construction operations were resulting in delamination of the fireproofing at the underside of the metal mansard roof deck. As a result, the restoration scope now included an interior repair component to replace the fireproofing. This additional work required close coordination between the general contractor and Memorial Hermann for access to the building interior. Hermann Pavilion The Hermann Pavilion consists of a 13- story tower and adjacent single-story to four-story buildings (Figure 14). The pavilion is clad with architectural precast concrete panels with punched windows and curtain wall and has a modifiedbitumen low-slope roof and clay tile steep-slope roofing. The pavilion houses Life Flight, which is the only hospital-based emergency air medical transport in the Houston area. The helipad and Life Flight operations are provided on the top two floors of the Hermann Pavilion 13-story tower. Significant hurricane damage was sustained throughout the pavilion, including damaged clay tiles, damaged glazing at window and skylights, damaged low-slope roofing, and water infiltration at louvered rooms housing mechanical equipment. Jones, and Cullen pavilions. This rotunda has a large aluminum-framed monumental skylight system for daylighting of the area (Figure 3). During original construction in the 1980s, impact-resistant glazing was not required. This skylight system sustained significant damage from wind-borne debris (Figure 2B). While outer panes of the laminated glass units were damaged from impact of clay tile debris, the lower panes remained intact, which prevented water infiltration to the building interior. The window systems of the Hermann Pavilion also sustained damage (Figure 2A). These systems were not originally required to have impact-resistant glazing. Even if they had, the majority of the damage to these systems was at the upper levels where impact-resistance glazing wouldn t have been required (greater than 60-ft. elevation). The window system glazing was composed of untempered insulated units, resulting in shards of glass from the impact of the clay tile debris but were held in place by the perimeter-insulated unit seal. To safeguard the building occupants, the area below the broken window units and skylights was cordoned off during the storm. During temporary repairs, safety netting was installed below the skylights, and overhead protection was provided within the rotunda so that it could be safely accessed by building occupants. Additionally, the broken units were removed and replaced with plywood while awaiting replacement glass. After the units were replaced with new glass units, the safety netting and overhead protection were removed. Low-Slope Roof Areas The lower low-slope roofs sustained damage from the wind-borne debris and were patched or replaced depending on the extent of damage. The low-slope roof replacements consisted of the replacement system that was adhered to concrete roof decks. The upper low-slope roofs did not sustain as much damage because these systems were at or just below the clay tile roofs. Membrane patch repairs and flashing repairs were performed at the upper lowslope roof areas. Clay Tile Roof Areas The clay tile roofs of the Hermann Pavilion sustained significant hurricane damage. These roof areas were suspected of causing a majority of the damage to the underlying roofing systems because they are the most elevated roof areas of the campus. There was also a concern regarding wind-borne debris damage and falling hazards during roof replacement operations. Therefore, safety netting was placed at the building perimeter to protect the occupants and underlying buildings during the roof replacement. Skylight and Window Glazing A portion of the Hermann Pavilion provides an open threestory rotunda for integrated access among the Hermann, Figure 14 View of Hermann Pavilion from the southeast. 2 7 T H R C I I N T E R N A T I O N A L C O N V E N T I O N A N D T R A D E S H O W M A R C H , P E E V E Y 9 1

12 Figure 15 The clay tile roof construction consisted of metal decking with plywood sheathing and a self-adhered underlayment with the two-piece barrel clay tiles set on stringers. An internal stainless steel gutter system was provided at the eave. The roof systems of the Hermann Pavilion were relatively new, and a majority of the clay tile roof assembly components were in good condition. Therefore, BES wanted to retain as many of these components as possible. However, the clay tile low-rise foam adhesive system had not been tested for compatibility and adhesion to the existing selfadhered membrane system. In addition, the membrane underlayment manufacturers that were approved by the foam adhesive manufacturer would not support the installation of their membranes over the existing membrane system. Removal of the existing membrane was costly and exposed the building to a higher potential of water infiltration during reroofing operations. Therefore, BES determined that the existing self-adhered membrane would remain in place and be overlaid with a new system. The replacement design incorporated a new separation layer of ¼-in. plywood decking over the existing membrane. The final roof replacement design was similar to that of the Cullen Pavilion, with a new plywood substrate mechanically fastened over the existing underlayment and the standard system overlaid on top. While BES was not able to reuse the existing membrane underlayment, the existing stainless steel flashing and gutter systems were retained as a part of the replacement design. In addition to compatibility issues within the replacement roof system design, there were construction issues. A major priority for the Hermann Pavilion restoration was that Life Flight operations would not be disrupted. Therefore, the roof replacement operations had to be carefully coordinated with Life Flight operations. In order to limit the potential for disruption, a system was developed so that BES, the general contractor, the subcontractor, and other personnel were notified of Life Flight activity and could take measures to secure all materials and allow personnel to evacuate the roof areas. These measures successfully allowed the roof replacement to take place with little down time, while allowing Life Flight to remain fully operational. Mechanical Room The louvered mechanical room on the 13th floor experienced a large amount of water infiltration during the hurricane. The water entering through the mechanical room s louvered openings migrated to the floor slab perimeter and through slab openings, infiltrating to the Life Flight Control room below. As a part of the restoration project, concrete curbs, vertical waterproofing for the wall finishes, and a waterproof floorcoating system were installed at the louvered mechanical room to prevent future water infiltration to the building interior below the mechanical rooms. Drainage at the louvered area was directed to the existing floor drains of the mechanical room. THE RESULT After about two years, the campus restoration was complete. The outcome was much more far-reaching than simple repairs. The campus not only was restored following the substantial hurricane damage, but preventative long-term solutions were incorporated into the restoration to prevent future catastrophic occurrences and to ensure the long-term performance of the campus s building envelope systems. Throughout the restoration, the project team coordinated with FEMA to ensure that the repairs met its guidelines and that all necessary documentation was provided to obtain funding. This coordination included periodic meetings and site observations with FEMA representatives, as well as collection of FEMA-required documentation. Documentation included records of the hurricane-damaged conditions, explanations of the extent and impact related to the hurricane damage for each roof area, descriptions of the repairs including code requirements that were met, and associated costs. The data were summarized by pavilion and provided to FEMA for its approval. In addition, the hospital was provided with a comprehensive evaluation of each of the campus s building envelope systems. BES created roof matrices (Figure 15) for each of the sections that provided detailed information for each roof system of the pavilion. A matrix for each pavilion was developed that inventoried each roof area s type, estimated square footage, condition, repairs performed, and anticipated remaining service life. These matrices have since been utilized for a roof maintenance management program for the campus, including the development of capital improvement budgets for the upcoming years. The end result to the perfect storm became the perfect solution with much hard work and collaboration of the perfect project team. 9 2 P E E V E Y 2 7 T H R C I I N T E R N A T I O N A L C O N V E N T I O N A N D T R A D E S H O W M A R C H ,