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Waterproofing Underlies Plaza Snow-Melt System

Friday, March 23, 2018

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Case Study By Tim Sullivan and Jason Walton, Kemper System America Inc.

 

Hartford, Connecticut, is no stranger to winter weather. There is about a 30 percent chance the ground will be white on any given day, and snowstorms with accumulation of a foot or more are not uncommon. This puts special emphasis on the details for a snow-melt system that was part of a major renovation project that consolidated offices for the State of Connecticut into two downtown towers.

 

THE PROJECT

The system, specified by Tecton Architects, of Hartford, was embedded below paver walkways and stretches across a pedestrian bridge above Columbus Boulevard. It also underlies a raised terrace between the two towers and Constitution Plaza, and heats multiple paths leading to the main entrances. The plaza level was designed for other seasons as well, with a public café and outdoor seating to foster intradepartmental and community connections.

Photos courtesy of Frank Capasso & Sons Inc. unless otherwise noted

The system, specified by Tecton Architects, of Hartford, was embedded below paver walkways and stretches across a pedestrian bridge above Columbus Boulevard.

The towers at 450 Columbus Boulevard, which feature a lobby between the two towers, required extensive upgrades to its 26 floors and five-story parking garage. A terrace dotted with planters extends over part of the garage, so like the heated walkways and plaza around the buildings, waterproofing was integral to the terrace design.

“The primary heat-melt for the walkways and terraces is a hydronic system with water and glycol running through plastic tubes, and that keeps ice from forming on top,” explained Tecton Architects Project Coordinator Bob Holmes. “We also did electric heat trace around the rest of the plaza where we were using pavers on pedestals so that all that melting water would not stay there, but melt and drain,” he said.

Heat-melt systems can reduce the need for salt and chemical ice melters, which can harm vegetation, and they also reduce the labor for winter maintenance.

The new system replaced a radiant heating system embedded in the original concrete. In this case, the hydronic tubing is flexible 3/4-inch PEX (cross-linked polyethylene) with the runs set about six inches on-center in compacted sand under pedestal pavers. The pedestals level the paver walking surface and create a space underneath for water flow. Below the pavers, the concrete deck for the walkways, terrace and plaza is sloped for drainage. The drains and the PEX runs for the heat-melt system could pose a special waterproofing concern because they penetrate the structural slab.

A cold liquid-applied reinforced membrane system from Kemper System America Inc. (West Seneca, New York) was selected to address the waterproofing challenges on the project, which included the base of the planters as well as the concrete topping slab, the curbs and the many penetrations.

“The penetrations were mostly for the snow-melt system, and the piping had to go through the slab to get connected underneath,” Holmes said. He noted that the team modified the original layout so pipes would pass through the base vertically rather than at an angle to achieve a better seal.

“The primary heat-melt for the walkways and terraces is a hydronic system with water and glycol running through plastic tubes, and that keeps ice from forming on top,” explained Tecton Architects Project Coordinator Bob Holmes. “We also did electric heat trace around the rest of the plaza where we were using pavers on pedestals so that all that melting water would not stay there, but melt and drain,” he said.

The Kemperol 2K-PUR membrane system was specified for the waterproofing. The solvent-free and odor-free system fully adheres to substrates and is reinforced throughout with a polyester fleece and protects at edges, corners and around drains and other penetrations. This seamless, self-terminating, fluid-applied membrane system is applied to details first, and is then installed into the field.

 

DRAINAGE AND WATERPROOFING

Frank Capasso & Sons Inc., of Northford, Connecticut, performed the installation as well as the restoration of the entire plaza. The original plaza construction, completed around 1982, consisted of a brick paver in a mortar setting bed and then a hot-applied waterproofing system on a structural deck.

The overall project included the demolition and removal of soil in the planters and brick paver system, as well as the installation of new walkways, the waterproofing and the pedestal pavers.

“When we removed everything, the plaza was pretty level, so we created slope with the concrete in the topping slab, pitching everything toward the drains, and then laid the waterproofing,” Project Manager Mike O’Neill said.

Before the waterproofing installation began, Kemper certified workers from Capasso & Sons on the application process, which started with the Kempertec epoxy primer with sand to key adhesion to the slab.

“We had about 10 guys on the job at any one time and they worked in different crews. Some laid out the primer, and a few more followed up and laid down the membrane system. Another worked on cutting the reinforcing fleece for the penetrations, the curbs, transitions and other details,” O’Neill said.

The fabric reinforcement is rolled into the polyurethane resin and then another layer of liquid resin is applied on top with a nap roller. Once cured, the result is a continuous membrane that can stand up to ice and ponding water, and resists rot, roots and most chemicals, as well as ultraviolet light.

The fabric reinforcement is rolled into the polyurethane resin and then another layer of liquid resin is applied on top with a nap roller. Once cured, the result is a continuous membrane that can stand up to ice and ponding water, and resists rot, roots and most chemicals, as well as ultraviolet light.

After waterproofing the field areas, crews installed a drainage mat and drainage board on top, then poured and packed the sand. In the areas with the snow-melt system, the tubing is set in the sand about an inch below the pavers.

Among the many waterproofing details were anchors for the pre-cast planters. The crew made a mortar with the system epoxies, and smoothed it over the anchors inside the planters so they could then apply the waterproofing. The planters drain onto the (waterproofed) terrace, but the waterproofing inside protects both the pre-cast concrete and the steel anchors. Exposed areas of the cured membrane system were coated with a Kemperdur DEKO finish to match the decorative planters.

The pedestrian bridge brings the advantage of the liquid-applied waterproofing system into focus. The bridge is about 20 feet wide, and the snow-melt system creates a 10-foot-wide path down the center.

“We had to place concrete curbs and dowel down into the deck. The curb was actually placed on top of the waterproofing system to contain the sand and keep it from spilling out onto the pavers,” he said. The waterproofing membrane was applied not only beneath the snow-melt system and paver areas, but up and over the curbs, including the inside rise at the sides of the bridge, O’Neill explained.

The plaza, terrace and walkway portion of the renovation project were completed in about three months.

“That curb went up 15-18 inches and then travelled horizontally across the top flat surface another 6 or 8 inches. All of that was waterproofed with the membrane,” he said. For the curbs around the raised plaza, the membrane was applied about 6 inches up the inside curb wall. Again, the membrane is self-flashing and self-terminating—there are no metal sheets or fasteners to cause leaks later.

The waterproofing membrane is water-resistant in about two hours and fully hardens to full traffic in three days. Weather delays after the waterproofing had been installed allowed heavy rain to leak-test the system before the next step.

The plaza, terrace and walkway portion of the renovation project were completed in about three months.

“It was a win for everybody, and the snow-melt system can help reduce the costs associated with snow and ice removal,” O’Neill said. “It is one of those jobs where everyone walks away with a smile.”

 

ABOUT THE AUTHORS

Tim Sullivan brings over 20 years of experience in roofing and waterproofing to his role as New England Regional Manager of Kemper System America Inc. He is responsible for business development with architects, engineers and building envelope consultants. Sullivan is an active member of CSI, RCI and AIA. Jason Walton brings over 17 years of experience in building restoration and construction to his role as Site Quality Control Manager for Kemper. He is responsible for overseeing critical projects across the U.S. as well as managing the warranty services department. Walton is an active member of ICRI.

   

Tagged categories: Case History; Kemper; Renovation; Waterproofing

Comment from Harman Metzger, (3/23/2018, 12:28 PM)

Interested to know what type or duration of warranty was provided for the plaza as a whole?


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