Cover Story

The Rev. Thomas Connolly had a lot riding on the tear-off and reroof of St. Charles Parish and School 
in Spokane, Washington.  Not only did the building complex serve as his home and the worship 
center for hundreds of families, the structure has historical significance.  Its construction preserves 
an important era in the evolution of modern architecture, featuring what is believed to be the only 
unbalanced hyperbolic paraboloid roof in the world.  Father Connolly also expected that the roofing 
work would be difficult.  But only an expert could predict just how challenging this roofing project 
would be.  Fortunately, the parish chose an experienced roofing contractor to handle the work and a 
world-class roofing manufacturer that offered a one-source guarantee on the myriad products this job required.
When discussing the details of the project with John Kidwell, president, and Darrell Kidwell, vice president, of All Surface Roofing and Waterproofing Inc. in nearby Deer Park, Washington, Father Connolly made the job sound relatively simple.  But any knowledgeable architect or roofing professional would know it was anything but easy.  First, Kidwell’s demo crew had to remove a layer of spray polyurethane foam (SPF) roofing that was breaking loose at the roof perimeters.  The SPF accounted for approximately 350 squares of existing low-slope roofing.  Beneath the SPF were two built-up roofing systems (BURs) and various coating products, some of which were asbestos containing.  What’s more, this conglomeration of roofing systems had to be carefully removed from existing wood and concrete decks.
As a state licensed asbestos abatement contractor in Washington, Kidwell’s crew was ready to don their moon suits and conduct the required air monitoring while removing the old roofing.  The contractor used a wet method for the abatement.  This involves dampening the roof surface before removing the asbestos-containing materials with tear-off spades and shovels.  After several days, laboratory tests confirmed that the asbestos materials would remain non-friable and not break loose and become airborne.  A dumpster was lifted to the roof surface for safe transport of materials to a truck where the debris was double-bagged, labeled, and taken to an appropriate disposal site.  At this point, the low-slope roof portions of the complex were ready for reroofing, and the existing steep-slope areas prepared as well.  As it turned out, the concrete hyperbolic paraboloid roof was the easiest to prep and reroof.

Three Roof Systems and One Guarantee
What made All Surface Roofing’s initial bid so attractive was its ability to link together three different roof systems:  high-definition asphalt shingles, TPO single-ply roofing, and the coating for the wing-like concrete roof, all under one roof manufacturer’s guarantee.  This also included roof underlayments, polyiso insulation, gypsum coverboard, and a large number of flashings and accessories.  “We’ve always had good experience using GAF products, but the company’s one-source guarantee was the key factor that sold the client on our specifications,” says Kidwell.  “Although this was a $500,000 project, quite frankly, it was an easy sell.  Our competitor did not think to offer a one-source guarantee.”
The list of products offered by the New Jersey-based roofing manufacturer is a long one.  GAF’s Tiger Paw(TM) roofing underlayment was used for the steep-slope roofs, and its WeatherWatch® Leak Barrier for the eaves, valleys, chimneys, and other vulnerable roof areas.  The asphalt roof shingle of choice was GAF Timberline HD® in Barkwood color.  On the low-slope roofs, GAF EnergyGuard(TM) PolyIso insulation and 1/4” gypsum coverboard were mechanically attached to the wood decks.  A tan-colored, 60 mil, EverGuard® TPO membrane was then fully adhered to the gypsum coverboard.
Over the low-slope concrete decking, All Surface Roofing spot-adhered the two layers of polyiso insulation and the gypsum coverboard with low-rise foam adhesive before fully adhering the TPO membrane.  With only 2” of existing perlite insulation on the low-slope roof sections, and spotty insulation coverage under the roof decks, the church structure was in dire need of insulation upgrade.  “You can often grandfather in the old insulation values on a reroof, but the parish opted for an R-30 insulation value from the double layer of polyiso, which should significantly enhance the energy efficiency of its buildings,” says Kidwell.  In addition, wherever any of the roofing systems met a vertical surface, Kidwell’s crews replaced all the flashing components.  If siding was present, it was removed, re-flashed and felted, and then re-sided.  The company also used 18 GAF Adjustable M-Vent flashings around all tall or awkwardly-positioned vent pipes and protrusions.

When Architecture Takes Flight
The concrete hyperbolic paraboloid roof was the easiest to waterproof, according to Kidwell, but was the most unique in terms of its design and historical significance.  Appearing like some sort of giant wing sitting above a building’s outer walls, the hyperbolic paraboloid roof structure was a startling and exciting addition to towns and cityscapes of the late 1950s.  Probably the most familiar hyperbolic paraboloid roof in the U.S. was the iconic TWA building at Idlewild (now JFK) International Airport in New York.  This bird-like roof was constructed in 1956.  The hyperbolic paraboloid roof offers a number of advantages to architects and building owners.  Because of its tensioned and curved structure, the roof requires no internal supports and only minimal contact with exterior walls and the anchoring concrete buttresses.  This makes them an ideal and expressive structure for clients requiring an open, light building design, and also makes them economical to construct.
In 1958, St. Charles Borromeo parish, founded in 1950 to serve congregants in the Shadle Park area of Spokane, set about building a new church alongside its recently completed school.  Using the local architectural firm of Funk, Murray & Johnson for design, a one-of-a-kind house of worship was erected, following a $324,832 fund-raising effort.  The church’s hyperbolic paraboloid roof is composed of a 3.5" thick shell made of concrete and reinforced steel.  It is held up entirely by the two points where it touches the ground, a construction made possible by a folding technique that makes the beams seven times stronger than normal.  This kind of construction had been used in Europe and Russia but was quite new in the U.S. at the time.  Construction began in 1959 and when finished in 1961, St. Charles church became the largest unbalanced hyperbolic-paraboloid roof in the world.  It is considered unbalanced because the sections of the shell roof that extend up and out from the two balance points are different in length, longer for the section over the seating area for 800 inside and shorter over the church entrance and baptistery.  In contrast, the TWA Building was much larger, but was a balanced design.
“Let’s just say that we were amazed by the structural capacity of that sloped concrete deck,” says Kidwell.  Fortunately for the church, the existing coating on the deck was in good condition.  The concrete surface only required a thorough pressure washing and cleaning before GAF’s TOPCOAT® was applied with a Graco HydraMax® 350 spray rig at a thickness of 32-38 wet mils.  TOPCOAT is a water-based, spray-applied liquid elastomeric roofing system, which cures to form a seamless 100% acrylic elastomeric membrane.  Kidwell considered using TPO on the irregular concrete surface but was concerned about the formation of wrinkles and air pockets after the TPO was fully adhered.  “All coating adhesion test-patch locations exceeded GAF guidelines,” says Kidwell.  “This will add years to the coating system, which only needs to be monitored and recoated as necessary.”

Never on Sunday
Kidwell and company carefully phased the four-month, 800-square project, which was completed last October.  Only the coatings crew needed to work on two Sundays to avoid inclement weather.  When school opened in the fall, the 675-family parish generated considerable pedestrian traffic, and Kidwell’s four-man shingle crew took every safety precaution possible during and after school hours.  “Despite the length and complexity of the project, we did not receive even one question from a church member or staff,” recalls Kidwell.  “Father Connolly did an excellent job of alerting and updating his congregation on the work in progress.”
Based on Spokane’s climate and light roof traffic, Kidwell estimates a 25-year service life for the three different roof systems, including a recoating of the hyperbolic paraboloid roof at an earlier date.  “Our priorities are that St. Charles remains a beautiful and safe place to worship,” says Father Connolly.  “From a roofing perspective, we also received guaranteed longevity, aesthetics, and a non-disruptive application that met our budget.”
A Heavenly Roof Design
Unbalanced Hyperbolic Paraboloid 
Roof in Spokane, Washington
by Gerry Messina, executive director, commercial marketing at GAF
Architectural West Magazine
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