To accommodate community growth, the Clarksville-Montgomery County School Board recently initiated a $44.8 million project to build a new elementary school on a 17.96-acre lot off Fort Campbell Boulevard in Clarksville, Tennessee. The new school, designed by Rufus Johnson Associates of Clarksville, was named Freedom Elementary School to honor the nearby Fort Campbell community. The school is nearly 105,000 square feet and will accommodate Pre-K through fifth-grade students.
The new construction project includes about 112,000 square feet of roofing on 14 different roof areas, at heights ranging from 15 to 30 feet, and several different shapes and slopes, including single slopes, hips and gables, and a barrel roof over the school’s main entrance. Modern Heating Cooling & Roofing (Modern) of Clarksville was selected as the roofing contractor for this critical project. “This is a critically important project for our community in terms of keeping up with population growth and student needs,” says William (Bill) Kimbrough Jr., vice president of Modern. “So, it’s important that we deliver a roofing system that will protect the facility for years to come.”
Most of the school was constructed with a 22-gauge steel deck; however, a 7,000-square-foot section along the front of the school building was constructed with a structural concrete deck. “The architects originally specified a standing seam roof for the sloped and visible sections of the roof,” Kimbrough says, “but that turned out to be quite expensive. So, with the help and input from the Carlisle Field Service Rep, we recommended using the Carlisle Contour Rib Profile system, which simulates the look of a standing seam roof with but with the performance of a PVC single-ply membrane.” Both the architect and the school board accepted the recommendation, and ultimately selected Carlisle’s 60-mil Sure-Flex PVC membrane in Slate Gray for the project.
The Sure-Flex PVC membranes is easy to install and weld, but it is also highly fire resistant, provides outstanding chemical resistance, and has higher breaking strength, tear resistance, and elongation properties than ASTM D4434 Type IV Specification Standards. “We like installing Carlisle PVC membrane,” Kimbrough says. “It’s easy to handle on the roof, welds well and is not as stiff or boardy as some other single-ply membranes. Our guys typically get great productivity with it.”
The Low Roof
The lowest section of the new school’s roof located across the front of the building is a rectangular shape approximately 233-feet long. The roof varies in width from 10.6 feet to 22.5 feet, with the short leg measuring 65-feet deep by 28-feet wide. This portion of the roof has a structural concrete deck with a series of seven internal drains. As a result, the entire roof required a fully tapered system to efficiently move water to the drains; this proved to be one of the more challenging parts of the installation. For this section of roof, the team from Modern first adhered two layers 2-inch InsulBase Polyisocyanurate Insulation with Flexible FAST Adhesive, followed by a complete tapered insulation to each of the drains.
Each of the drains required four-way sumps, which resulted in a series of ridges and valleys across the long axis of the roof. In addition, the Modern team installed a variety of two-way crickets along the front and rear edges of the roof, as well as between some of the tapered sections.
“The roof was very narrow, sloped in four different directions, and had multiple HVAC stands that had to be carefully flashed, so the work was slow and the guys had to be extra careful,” Kimbrough says. On top of the tapered insulation, Modern then installed ½-inch SecurShield HD Polyiso with Flexible FAST Adhesive. “The Flexible FAST Adhesive is very easy and efficient to use, and we can get some great productivity with it,” Kimbrough adds. Once the SecurShield HD was installed, the team could move forward with adhering the membrane using Sure-Flex PVC Low-VOC Bonding Adhesive, a high-strength contact adhesive specially formulated for PVC membranes.
The team applied the adhesive to both the polyiso and the bottom of the membrane, allowed it to flash off, and then rolled the membrane in place for maximum contact. Once the membrane was down, they heat-welded the seams and terminated the membrane around the perimeter.
The Contour Rib System
The sloped and visible sections of the roof all had steel decks. For those sections, the Modern team loose laid two 2-inch-thick layers of 4 x 12-inch InsulBase Polyiso Insulation, which went down quickly due to the size of the boards. This was followed by a layer of ½-inch SecurShield HD that was mechanically fastened through the insulation below to the deck using InsulFast Fasteners and 3-inch insulation plates.
“The 12-foot insulation was a real productivity driver for us,” Kimbrough says. “We like using it whenever we can because it goes down fast and really helps to move projects along quickly.” After installing the membrane, welding the seams and terminating the membrane with shop-bent drip edge fascia made with matching Slate Gray clad metal, the Modern team started to install the Contour Ribs. “Getting each of these sections dried in quickly was important so that the internal work could continue on time,” Kimbrough says, “but we still had work to do in terms of installing the ribs.”
Sure-Flex PVC Contour Rib Profiles are 1 ¼-inch tall and 2 1 ⁄8-inch wide (including the welding flange) and come in 10-foot lengths. Each has a 1⁄8-inch alignment hole and a fiberglass reinforcing pin that is installed between each section to ensure that they remain in a straight line. Ultimately the ribs are heat-welded in place. “This was our first job using the Contour Rib system,” Kimbrough says. “There was definitely a bit of a learning curve because it’s immediately apparent that the ribs must be installed perfectly straight and align perfectly with the structure. Any variation would be very noticeable from below and would ruin the look we are going for.”
To get the alignment correct, the Modern team first snapped chalk lines but decided that the ribs could “walk” a bit during the alignment. “To ensure that the ribs remained perfectly straight, we fabricated a wooden ‘guide’ as a straight edge that we used to keep the welder running straight. We had one person running the robot welder, and four people moving the wooden guide to keep up with the welder.” Modern finished the installation using a variety of custom-fabricated boots and corners to match the Slate Gray membrane.
In addition, around the perimeter of the main roof areas, they installed Carlisle SecurEdge 200 snap-on canted fascia. The fascia is ANSI/SPRI/FM 4435/ES-1 tested and Factory Mutual approved for wind uplift and offers maximum protection for the new school’s roof.
ABOUT THE AUTHOR: Information provided by Carlisle Syntec Systems. For more information, go to carlislesyntec.com.
TEAM:
ARCHITECT: Rufus Johnson Associates, Clarksville, Tennessee, rufusjohnsonassociates.com
ROOFING CONTRACTOR: Modern Heating Cooling & Roofing, Clarksville, (505) 514-9488
MATERIALS:
ROOFING SYSTEM: Sure-Flex PVC membrane –Slate Gray; Sure-Flex PVC Contour
Rib Profile; Sure-Flex PVC Bonding Adhesive; ½-inch SecurShield HD Polyiso, Carlisle Syntec Systems, carlislesyntec.com
