vertical accessquarterly  Industry news and perspective from Vertical Access LLC    Volume 2, Issue 1, March, 2005

helping architects and engineers deliver superior design documents  


In this issue...

Guastavino and VA

Technical Highlight: Radar NDE

Hanging Flume Update

New York City Center: In Construction

Flying in Michigan


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Guastavino Projects

Vertical Access first gained exposure to Guastavino tile while inspecting the interior vaults at St. Thomas Church in New York City in 1996.  Almost ten years and half a dozen Guastavino projects later, Vertical Access has developed an expertise in the inspection and evaluation of this remarkable structural and decorative material.

old guastavino tileRafael Guastavino adapted a form of the timbrel (or Catalan) vault in which thin bricks or tiles are adhered together with a quick-drying mortar to create a laminated, thin shell-type structure. After earning a reputation in his native Spain building factories, mills and elaborate homes, Rafael Guastavino left for the United States in 1881.  Eventually endorsed by the architectural community here, Guastavino contributed to more that 1000 historically significant buildings in the United States.

Guastavino tile has experienced a resurgence of interest in the past five to ten years, owing to the work and forsight of three individuals.  The construction technique was ultimately made available to preservationists through the work of George Collins, a long-time faculty member in the Art History and Archeology Department at Columbia University. Having followed the rise and fall of the Guastavino Company, when he learned of the company's impending dissolution, Collins facilitated the donation of the archive to the Avery Fine Arts Library at Columbia.  Since Collins' death in the late 1980's, Janet Parks and Alan Neumann were instrumental in cataloging all the components of the archive, which culminated in a gallery show and book: The Old World Builds the NewAPTI (The Association for Preservation Technology International) and NYLC (New York Landmarks Conservancy) increased exposure when it presented a one-day symposium in 1999 on the subject of Guastavino.  The proceedings of this symposium, along with reproductions of the Guastavino patents are collected in a dedicated issue of the APTI Bulletin.

guastavino tile in st. thomas churchWhen we first worked with St. Thomas Church, it had a fixed budget to spend on renovation and wanted to ensure that the interior of the Guastavino vaults were sound to preserve funds for the higher-priority exterior renovation work.  A close visual inspection and live-feed video were employed to investigate four suspect areas.  In the end, Vertical Access was able to complete the inspection for about 15% of the cost for scaffolding to be built for the same purpose.

Another recent VA project was the sounding at St. Paul's Chapel on Columbia University's campus.  VA was brought on by Robert Silman Associates to aid in sounding the Guastavino from a DENKA lift.  This lift has a 90 foot vertical reach with the 10 foot jib boom extended and allowed VA to reach every area of the Guastavino.  The structural Guastavino was found to be in excellent condition, with problems only in the small Maltese cross tiles lining the windows.  These ornamental tiles were applied over the structural Guastavino tiles, and had delaminated. 

Highlighting Vertical Access exposure to Guastavino projects, Kent Diebolt gave a presentation at Les Estructures Historiques...Substiticio o Conservacio in Barcelona in December.  Chuck DiSanto of Walter Melvin Associates also spoke on the Queensboro Bridge project.  Also, an in-house research pilot study of using ultrasonic frequency response for the evaluation of delaminated Guastavino tiles has shown very positive initial results.  Kelly Streeter presented the findings of this pilot study at the APT northeast chapter meeting in New York in March.  Funding is currently being sought to continue this research.

Upcoming Guastavino projects for Vertical Access include the Oyster Bar and the Federal Reserve Bank, both in New York City, and the Plymouth Monument in Massachusetts.-Kelly Streeter, Photos by Jon Reis

Both The Old World Builds the New and The APT Bulletin published in conjunction with the February 1999 symposium are still available.  Please go to and the Avery Library site for more information.

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Technical Highlight: Ground Penetrating Radar

ground penetrating radar reflections
Figure 1

Ground penetrating radar, also referred to as georadar, earth sounding radar, or surface penetrating radar, has been an emerging technology since its commercialization in the 1970's.   It is used in a wide range of applications including utility detection, forensic investigation, archeology, and the inspection of concrete, bridges, highways, architectural facades, rail beds, and airports.  GPR can provide valuable information about the subsurface of the ground or a building component by nondestructively revealing voids, layers, and the presence of other materials such as metal or plastic.

Radar works well for examining any material with low electrical conductivity.  Electromagnetic energy travels through substances at velocities determined by the dielectric of a material.  Reflections of this energy are caused by changes in dielectric properties of materials.  As the signal travels through a medium like a concrete slab, materials such as steel can cause a reflection due to the difference in dielectric between the two substances.  This reflection is visualized as a hyperbola on the time domain (Figure 1).  A series of survey lines in two perpendicular directions can be used to create a grid.  This data can be analyzed to create depth slices (Figure 2) or a 3D interpretation of targets at various depths in a scanned area (Figure 3).

surface penetrating radar graph
Figure 2

Equipment for performing a GPR survey includes a radar control unit, antenna, and data storage device.  The control unit sends a trigger pulse to the transmitter in the antenna which is transformed into an electromagnetic pulse.  At the same time, the storage device is alerted to start recording data.  The size, shape, and configuration of the transmitting antenna determine the frequency, bandwidth, and beamwidth of the signals emitted.  After transmitting the pulse, the antenna switches to receive mode, and energy reflected from changes in dielectric is picked up and passed back to the control unit, which converts the signal to digital form.  Individual radar pulses are generated and reflections are recorded continuously at a rate chosen by the user, but typically 50 to 100 pulses are recorded each second.  The subsequent series of reflected waveforms is analyzed by the equipment operator, ranging from hyperbolic shapes for pipe-like targets to planar reflections from larger anomalies.  Alternatively, data may be stored on the processor for later analysis in the office with post processing software.

Ground penetrating radar is an effective tool for looking at what may be beneath a surface nondestructively.  This technology could aid in determining the structural configuration of existing structures and finding voids or fractures in facades.  In many cases, the use of nondestructive techniques is the most cost effective means of acquiring desired data about a structure. -Shan Wo of Atkinson-Noland and Associates, Inc.

3D ground penetrating radar diagram

Figure 3

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Hanging Flume Update

vertical access workers at the hanging flumeSince Vertical Access's involvement with the Hanging Flume Project in April of 2004, the 120 year old structure has had much exposure in the historic preservation community both at home, in Colorado, and abroad.  Ron Anthony of Anthony & Associates gave a talk to the Denver Mining Club in late January. Ron and Kent Diebolt of Vertical Access co-authored and presented at The Colorado Preservation Inc. (CPI) in early February. Justin Spivey of Robert Silman Associates, P.C., gave a talk at the International Conference on Conservation of Historic Wooden Structures in Florence, Italy, entitled "Investigation of the Construction of a 19th Century Wooden Flume Suspended on a Cliff." Jack Pfertsh of Alpine Archaeological Consultants, Inc. gave a paper on the archaeology of the flume at The Colorado Council of Professional Archaeologists (CCPA) in March.

Separate from the structural engineering condition survey of the flume was a cultural resource survey, including four oral interviews, which has been recorded and transcribed, and the archaeological findings and GIS mapping of the flume by The Alpine Archaeology Co.

Project manager Ron Anthony, who supplied the information for this update, continues to be active in supplying the State Historical Fund with progress reports on behalf of The Western Colorado Interpretive Association. Ultimately, they will receive from him a condition report which will include a plan for the mitigation of future deterioration of the flume, as well as a compendium of all the research that was done by the various participants in the project. Facilitated by the data collected during this project, Cultural Resource Planning will then complete their "master plan" for the flume.

The Hanging Flume was nominated for The World Monuments Fund Watch List of 100 most endangered sites. The outcome of this nomination is still pending. If the nomination is accepted, the hanging flume may be eligible for funding for preservation and community education.

For an in-depth article on the background of the hanging Flume Project, visit the July 2004 Vertical Access Quarterly.-Stardust Atkeson, Photo by Jon Reis

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New York City Center: In Construction

new york city center buildingThe ornate New York City Center building was originally constructed by the Shriners with faux-Moorish details by the architects, Harry P. Knowles and Clinton & Russell.  Nearly turned into a parking garage in the 1940s, the building was rescued by Mayor LaGuardia, who opened it as the city's first performing arts center in 1943.

In recent years, City Center has been a performance space for the Alvin Ailey American Dance Theater, the Paul Taylor Dance Company and the American Ballet Theater, as well as for theater presentations like the ''Encores! Great American Musicals in Concert'' series.

Although the present renovation is to include a large general restoration, the crux of the project has always been the renovation of the monumental terra cotta dome, which Vertical Access inspected in February 2002, in conjunction with Helpern Architects.  

Constructed of Spanish tile commonly found sheathing more traditional roof types, the 104 foot diameter dome is the only graduated clay-tile dome in the Northeast.  It is constructed of 28,475 clay tiles that become increasingly narrow from bottom to top.

One of the great challenges for the dome's reconstruction is to maintain its authentic appearance.  To achieve this, three different colored terra cotta tiles were chosen to be laid in a random pattern.  These new tiles were fabricated by Ludowici Roof Tile of New Lexington, Ohio, creators of the original tiles for the dome. 

The full article can be downloaded from the New York Times website: -Kelly Streeter

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Flying in Michigan

flying in michiganAfter the recent mid-year APT Board of Directors meeting at the Cranbrook Institute, near Detroit, Past President Kent Diebolt and Director Steve Kelley took turns flying with "ace" Staley, former treasurer and secretary of APT.

Ron owns a 1943 T-3 Texan airplane, which was an used as an advanced fighter pilot trainer during World War Two. -Kent Diebolt


flying in Michigan 2 flying in Michigan 3
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