Book Cadillac Hotel – Detroit, MI

Built in 1923 at a cost of over $14 million the Book Cadillac was the shiniest jewel in Detroit’s crown. At 33 stories in height and with three basements, the Book Cadillac was not only the tallest building in Detroit it was the tallest Hotel in the world.

Constructed with a steel column and frame, riveted together, supporting the formed concrete floor slabs and exterior façade. The horizontal beam elements were encased in concrete as part of the floor construction operations. Large built-up steel trusses on the 6th floor (original Duct floor) transferred the column loads from the hotel rooms above to clear span the meeting, banquet and ballrooms below. The structure extends three levels below grade with the basement levels housing the back of house equipment such as laundries, coal fired boilers etc. The exterior walls were constructed of a complex mix of materials with clay tile backup bearing on exterior spandrel beams tied to exterior brick, sandstone, terra-cotta or copper veneer. Vertical and horizontal bands of sandstone, terra-cotta with columns, statues, balconies and water-tables decorated the main elevations.

The Book Cadillac Hotel stood vacant since the mid 1980s. It was stripped of its interior architectural features, the site of a number of fires, home to vagrants, and the subject of demolition discussions. Standing vacant for over two decades resulted in moderate to severe deterioration to the exterior façade and structural skeleton. Water leaking into the interior upper and lower levels resulted in corrosion of steel members and the disintegration of concrete floors due to freeze/thaw action. Water leaking into the exterior façade and horizontal water tables resulted in corrosion of the exterior steel beams, connections and sandstone/terra-cotta embedded connections. The Ferchill Group’s $170 million restoration project, undertaken as a preservation tax credit incentive project, was carried out in three parts: Interior Building Stabilization Project, Exterior Façade Restoration Project and New Addition Project.

The Interior Building Stabilization Project began with a detailed condition assessment that included the visual inspection of all walls, columns, beams, slabs and connections. Structural components that were suspected of deteriorations were tagged for further testing or selective demolition for further review. Concrete core test and rebound hammer tests were used to determine the condition of the concrete floor slabs. Test specimens taken from steel beams and columns were analyzed to determine the weldability and the yield stress of the steel.

Floor framing plans, based of the original structural drawing were used to detail building stabilization work required on each floor. Various details and techniques were developed and used to reinforce/repair or replace existing elements that had deteriorated, fill in existing openings, or reinforce existing framing for new loading conditions.

The Exterior Façade Restoration Project was lead by Sandvick Architects with Desai/Nasr Consulting Engineers providing structural engineering services. A detailed visual review of the exterior façade was carried out from the contractors swing stages. Areas of concern or showing signs of deterioration were identified and investigated. Inspection pockets in the brick veneer were used to assess the condition of the steel spandrel beams, columns and connections buried in the exterior façade. Sandstone and terra-cotta element were removed to review the condition of the existing connections.

Vast lengths of existing terra-cotta water tables and back-up steel support beams were removed and replaced with new galvanized steel members and molded glass fiber panels to maintain the historic appearance of the façade. Over 1000 lintels were removed and replaced with new galvanized steel lintels with proper flashing and weeps. Large areas of brick were removed and replaced with new brick.

The entire north tower was deemed to be structurally un-safe and was completely demolished down to the 29th floor before being re-constructed out of steel framing with brick and stone veneer to preserve the historic architecture.
Every window in the building was replaced with new aluminum framed windows. Special details were developed to support the new window sub-bucks back to the existing masonry walls. New steel or cold formed metal stud post and header framing was introduced at the large window openings to provide lateral to resist wind loads as required by today’s building codes.

The New Addition Project included a three story addition to the north side of the existing building. Constructed over the site of various previously demolished building with existing basements and foundations, the new addition is supported by deep drilled piers supporting the steel framed building and reinforced concrete grade beams and structural concrete ground floor slab. The structural ground floor slab supports the new swimming pool, loading dock, restaurants and other back of house facilities for the new Westin Hotel. The upper levels of the new addition house part of the hotels main kitchen and a new banquet areas located above the new swimming pool.

Lessons learned:
Desai/Nasr was introduced to the project after the construction documents were presumed to be 65% complete. On careful review it was found that new structural framing added to support floor openings and other modifications could not be practically installed. The new steel beams detailed below the existing floor structure would not leave sufficient head room below these areas. This resulted re-design of all the additional framing, substantially reducing the amount of additional steel required.

Over 1200 existing openings in the floor slabs needed to be filled throughout the tower. Desai/Nasr and Marous Brothers (the Contractor) spent time and effort developing the most cost effective solution. Communication between the design engineer and contractor, along with a few thousand dollars spent on load tests, saved the project hundreds of thousands of dollars.

Dealing with a historic building that had been left abandoned for 20years resulted in areas with significant concrete deterioration and corrosion of structural steel. Many of these issues were not visible during the initial assessment of the building as they were concealed by finishes, inaccessible or flooded. Desai/Nasr was “on call” during the entire construction phase, available to be on site to assess exposed conditions provide input and keep construction teams working. Adequate time allowance and quick response by the Structural Engineer is required for a successful project when dealing with historic buildings.

“Desai/Nasr was flexible with their design and through value engineering efforts saved the project more than a million dollars in material and labor costs. Whenever unforeseen conditions presented themselves on site a Project Engineer would come out to assess the condition and would quickly issue a solution…..” Lee Tucker, Project Manager Marous Brothers Construction.