Trial by Fire: Structural Engineering Challenges in a Historic Hotel Conversion

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What is today a Tribute Portfolio Marriott Hotel in Frederick, Maryland, was once an all-girls Roman Catholic school that dates back to the Civil War era.

The Visitation Academy, founded in 1846, originally consisted of a large three-story building and was later expanded through multiple additions. The main building and its additions are constructed primarily of mass brick masonry walls with wood framed floors and large, heavy timber roof trusses. After nearly two centuries of establishment, the Visitation Academy was seeing a decline in enrollment and ultimately decided to close its doors in 2016. A developer purchased the property in 2017 with plans to convert the building into a boutique hotel. Wanting to keep as much of the history of the building as possible while also modernizing the space, the Visitation Hotel became a quintessential adaptive reuse project.

An adaptive reuse project typically involves the renovation of a building or space for a new purpose while keeping the majority of the structural framing and components. Often times, strengthening or other modifications are required to meet the new function and aesthetics of the space as well as updated code requirements.

Originally primarily used for classrooms and sleeping quarters, the majority of the building was subjected to roughly 40 pounds per square foot of live load. Today, some of these same spaces are being used for the hotel lobby, fitness center, egress pathways, and dining areas which have higher loading requirements to meet today’s building code. In several areas, the existing floor joists required strengthening with new laminated veneer lumber (LVL) sisters to meet new loading requirements as well as deflection criteria for occupant comfort. In other areas, it was desired to keep more of the historic fabric intact, thus strengthening of the existing floor framing was not an option. The existing floor framing in these areas could not support the new live loads required to comply with the designated occupancy per the International Building Code. Instead of sistering, the existing floor framing was evaluated for a reduced live load that was determined based on the size of the space and the number of people that were expected to use the space at a given time. This approach is allowed per the International Existing Building Code for alterations and requires placards to be displayed in the area where the live load is limited.
In addition to upgrading the floor framing to meet new loading requirements, the new programming of the space required several new, large openings in the existing load-bearing brick masonry walls. These openings required wide-flange steel beam lintels to support the weight of the mass masonry wall and floor framing above while also meeting tight deflection criteria.

Several areas of the building also needed upgrades to meet current Americans With Disabilities Act (ADA) requirements. Ramps were constructed throughout the building and three new elevators were added. At two of the elevators, the depth of the elevator pit exceeded the bottom of the existing footing bearing elevation, requiring underpinning of the existing foundations. Additionally, where the elevator shafts utilized existing masonry walls, several masonry repairs were required to establish a suitable substrate for the elevator rail attachments. The elevator in the east wing of the building also required a pop-up at the roof level to provide enough clearance for the elevator overrun. From a historic standpoint, it was important that the construction of the overrun blend with the original construction since it was on a prominent corner of the building.

Construction began in early 2022 and was targeting completion in late spring of 2023—just in time for wedding season. A couple of months before construction was anticipated to be complete, the schedule was significantly impacted by a fire in the west wing of the building during a severe thunderstorm on the night of April 1, 2023. The fire damage was localized to one wing of the building and in areas with two distinct structural framing systems. Existing roof framing in the southern portion of the west wing consisted of heavy timber trusses spaced approximately 12 feet apart and spanning roughly 40 feet. The trusses were supported on masonry pilasters within 25 foot-tall mass masonry bearing walls. Wood purlins and rafters spanned between the trusses and were topped with wood decking. Existing framing in the northern portion of the west wing consisted of 3x6 wood rafters spaced 24 inches apart supported on masonry bearing walls, and a series of timber posts and beams which also framed an exterior balcony.

The fire caused severe damage to the building. Before repairing the historic building, it was critical to understand the extent of structural damage. When assessing a damaged structure, safety of personnel is of paramount importance. The first step in the assessment included a survey around the exterior perimeter of the building to understand the general locations of damage and identify any potential hazards such as unstable masonry, damaged handrails, and compromised floor and roof areas. Engineers then inspected the interior of the building starting at the lowest levels and working their way up, ensuring they did not step on fire-damaged wood framing that could no longer support weight. The extent of the fire damage presented significant challenges when it came to accessing the attic framing and roof trusses. Ultimately, the team determined that a custom-built scaffolding system was necessary to facilitate a hands-on inspection of these components.

Hands-on inspection is important to gain an understanding of the remaining cross-sectional properties of fire-damaged wood structural members. When exposed to fire, the outer layer of timbers becomes charred, but this outer char layer can often be scraped away revealing a reduced, but still potentially viable, structural cross-section. The zone beneath the char layer (i.e., the pyrolysis zone) experiences thermal degradation, affecting the load-carrying capacity of the wood framing. However, wood below the pyrolysis zone retains its strength and a residual cross section of a fire-damaged timber can be analyzed for structural loads. The United States Department of Agriculture’s (USDA) Wood and Timber Condition Assessment Manual and the 2024 Edition of the National Design Specification (NDS) provide guidance to determine section properties of residual cross sections.

After inspection and review, the engineering team determined that the fire damage was too extensive, and the remaining cross-section of the attic and roof framing was not adequate and thus needed repairs. Several different options for repairs to the fire-damaged structure were explored. Ultimately, replacing the framing in-kind (particularly the heavy timber trusses) was deemed problematic due to cost and schedule concerns, and the team decided to remove much of the fire-damaged framing and replace it with new metal plate-connected (MPC) wood trusses.
Given the lightweight nature of the new roof trusses, uplift forces due to wind had to be carefully considered. New anchorage details and lateral bracing were designed to counteract potential uplift, ensuring the roof system remained stable under wind loads. Coordination with the architect and contractor was crucial to integrating these structural elements without compromising the historic character of the building.

The significant damage to the roof also put the existing exterior masonry walls at risk of collapse due to compromised bracing. To provide stability, temporary wall bracing was installed that consisted of a combination of diagonal wood and steel members anchored to stable portions of the structure. This temporary support system remained in place until the permanent structural repairs were installed. The design of temporary bracing was delegated to a specialty shoring engineer and carefully reviewed by the Structural Engineer of Record.

MPC trusses are commonly used for their efficiency and cost-effectiveness, but they are also prone to fabrication and installation flaws. Typical issues include improper handling and on-site storage of trusses, truss plates installed with wane or wood with other defects, and improperly installed bridging or bracing. Each defect requires careful evaluation and coordination with the MPC truss delegated design to determine whether repairs or replacements are necessary.

Adaptive reuse projects can often create more challenges than new construction due to constraints of the existing structure and unforeseen conditions.

One of the greatest lessons learned during this project was the importance of confirming existing conditions early on in the design and establishing construction contingencies to account for both cost and schedule impacts for unforeseen conditions. The original structural drawings for the building were not available to the design team; therefore, exploratory openings were made at select locations prior to the start of the design phase to verify the existing framing. However, these openings were limited, and several conditions were made much more apparent once the full demolition of finishes for construction took place. This resulted in several Requests for Information (RFIs) during construction and redesign of several elements based on the existing conditions.

Additionally, since several areas of the building were heavily modified to meet the new function of the space, it was important to understand the load path of the original construction and verify that the new structural framing could follow the same load path or that a new load path would be established to the building foundation. For example, the columns supporting the balcony in the chapel did not have a clear load path down to the building foundation. A new steel beam was installed to transfer the balcony column reaction to two new steel posts and concrete foundations. Another example is a unique framing system was designed for the MPC trusses. Typically, structures framed with MPC trusses consist of closely spaced trusses supported on load-bearing walls or beams. However, this framing scheme was not consistent with the existing load path in the southern area of roof damage. The new framing plan consisted of 2-ply MPC trusses sistered to the existing timber trusses and supported on the existing masonry pilasters to mimic the load path of the original timber trusses and wood purlins.

Developers can easily purchase a property and demolish the entirety of a building to create something new and more modern. However, as sustainability gains more and more traction in the built environment, projects like the Visitation Hotel will continue to be of great importance. Not only is adaptive reuse often a greener alternative to new construction, the majority of the building, including its historical integrity, was saved.

The Visitation Hotel in Frederick, Maryland, is a beautifully reimagined space and serves as a great place to stay, grab a bite to eat, or hold a special event. Although the fire damage and necessary repairs set the construction schedule back from the original completion date, the Visitation Hotel officially opened for business in December of 2024. The hotel and its acclaimed restaurant by the Voltaggio brothers, who are known for their appearances on Top Chef and Food Network, cement the project as a landmark destination in Frederick. ■

About the Author

Chelci E. Dell is a Senior Consulting Engineer in the Structural Engineering Division of Simpson Gumpertz & Heger's Washington, DC, office.

Jeffrey D. Viano is a Senior Project Manager in the Structural Engineering Division of Simpson Gumpertz & Heger's Washington, DC, Office.