Fountain Place in Dallas is an architectural wonder known for its “dancing” water gardens at the base of a dramatically sculpted, reflective glass office tower designed by I.M. Pei. When the time came for the water features to be renovated, the building’s ownership group and primary engineer wanted the garden to be leak proof well beyond the level the original waterproofing materials afforded.
“The water gardens were originally constructed above a parking garage with thousands of concrete cold joints, using separate pours not really designed to be waterproof,” says Gary Bennett, owners group representative. “Vertical to horizontal concrete components were sealed with various waterproofing products that were not completely designed for the condition in which they were used.”
The Fountain Place renovation consists of nearly two acres of cascading waterfalls, pools, fountains, and elevated walkway pavers, and proceeded under Mobile Enterprises, the specialty commercial architectural and structural contractor whose water garden contract called for concrete repair, waterproofing, and paver replacement.
Elastomeric coatings had been primarily used to waterproof Fountain Place’s water features, but deteriorated over time and led to water leaking into the parking garage below. “The original design used polyurethane based elastomeric coatings over 20 years ago,” notes Mobile Executive Vice President John Pierce. “While these have UV resistant topcoats, over time exposure to chlorine in the water as well as outdoor UV rays begin to bake those membranes. They become soft and chalky … susceptible to substrate movement and prone to leaks.”
Water feature location presented additional challenges, he adds: “The fountains are built over a concrete parking structure that is moving as cars drive around looking for spaces. The parking deck’s top slab is made up of precast planks with a topping slab.”
Any water feature waterproofing must also accommodate daily and seasonal temperature changes, which can cause concrete substrate movement—likewise leading to leakage over time. “Mid Texas summers are hot and winters are cold,” Pierce explains. “This will cause water feature concrete expansion as higher temperature water flows in summer and contraction as colder water flows in winter. Thermal cycling between day and night can also cause some substrate movement.”
According to Bennett, all the substrate movement was well beyond the original waterproofing products’ capability to maintain constant performance. Despite these challenges, any waterproofing used in the rennovation had to endure concrete substrate movement and still not leak.
Pierce says that some of the Fountain Place’s pools above the parking garage had been remediated with a PVC roofing membrane with heat welded seams, but still had leakage issues. “Most waterproofing materials with heat welded seams must remain fully adhered to the substrate,” he notes. “However, moisture in the concrete can diminish the membrane’s adhesion, leading to gaps and water leakage. This is one reason that a seamless system is often preferred over a seamed system.”
Many traditional materials would also not be up to the task of waterproofing, he adds, noting, “Materials like plaster, epoxy, or tile would need to have an underlying elastomeric membrane to function because anything rigid would crack and leak. Being constantly submerged and not being chemical resistant can also cause problems to the underlying membranes.”
Instead of less durable coatings and traditional pool membranes, Fountain Place’s ownership group and primary engineer selected an elastomeric polyurea basecoat and topcoat combination from VersaFlex, a global supplier of high-performance architectural coatings, liners and joint sealants. As part of Fountain Place’s restoration, Mobile Enterprises removed water feature materials down to the original structure, as well as paver stones in plaza area walkways.
|A 60-mil basecoat of FSS 45DC and a 20-mil layer of GelFlex, both by VersaFlex, were used to create a tougher, more aesthetic membrane for the Fountain Place.|
After completing necessary concrete repairs and priming water feature areas, the company sprayed a 60-mil basecoat of VersaFlex FSS 45DC or waterproofing. The spray-applied polyurea basecoat creates a seamless, waterproof, durable protective liner that stops leaks and strengthens the integrity of the entire structure. It exhibits superior physical properties such as high elongation, crack bridging, hardness, and tensile strength to create a robust, resilient, puncture resistant liner. It is also designed to withstand wide variations of temperature and humidity including decades of freeze-thaw cycling.
“The polyurea basecoat provides a seamless, flexible, waterproof membrane system,” says Pierce. “It is flexible enough to accommodate structural garage movement, ground movement, as well as daily or seasonal expansion or contraction due to temperature changes. Anytime you deal with concrete, crack bridging properties are important.”
On top of basecoat, Mobile Enterprises sprayed a 20-mil layer of GelFlex, an aliphatic chemical resistant, UV color stable, 100 percent solids, polyurea topcoat. “GelFlex bonds seamlessly, tenaciously to the basecoat,” says Pierce. “It provides chemical and UV resistance as well as a high gloss, color stable, aesthetic look designed to last decades.”
Together, the polyurea basecoat and topcoat “provide a much tougher, more aesthetic membrane for the long haul than other softer elastomeric coatings,” adds Pierce, who also reinstalled an elevated paver pedestal system at Fountain Place by Wausau.
Spraying of the polyurea basecoat and topcoat is achieved with a plural component spray gun connected to a long heated hose and pump machine. Unlike a traditional two-part epoxy topcoat with a short pot life, the polyurea products’ components are mixed in the spray gun nozzle during application so there is no pre-mixing needed and essentially no waste in the process.
Pierce notes that the fast setting polyurea basecoat and topcoat offer other advantages in application as well. “Since they each set within 30 seconds, you can walk on them in a minute,” he says. “After an hour, you essentially have a fully cured membrane, so if you have some afternoon rain, it will not set your project back.”
“The polyurea basecoat and topcoat combination works really well, both functionally and aesthetically, for Fountain Place,” Pierce concludes. “Any property with water features— such as hotels, resorts, parks, convention centers, or commercial pools—would benefit from such an application.” — Prepared by Del Williams, Torrance, Calif., for VersaFlex Inc., Kansas City, 800/321-0906