The study confirmed that windows and caulking were among the worst offenders, and the building's pre-cast concrete exterior was showing early signs of deterioration.

"The original windows were a single-pane design," Jones said. "They probably weren't the best choice for a coastal high-rise, and they wouldn't meet current codes for new construction."

Although the entire building was re-caulked in the 1980s, the urethane sealants were also showing signs of failure at the time of the study. In addition, water repellents applied to the building's exterior 10 years prior needed re-application, as they had delivered inconsistent protection and were causing parts of the building to show dark blotches.

The engineering consultant on the Atlantis renovation is Joe Shuffleton, a professional engineer and owner of Engineering and Technical Consultants Inc., Sterling, VA, who has been involved with the building since the 1980s. Based on 30 years of experience in construction, Shuffleton specified Dow Corning‚ 795 Silicone Building Sealant, a neutral-cure, high-performance material, for more than 600 new double-pane aluminum windows and sliding doors in the 200-unit structure.

"We needed sealants that would stand up to pounding rain, chlorides from the ocean air and windblown sand that comes blasting in from the beach," he said. For control joints in the pre-cast concrete, Shuffleton selected 790 Silicone Building Sealant, an ultra-low modulus formulation with a reputation for excellent service in buildings with extreme movement.

Exterior Walls: A Sealing Challenge

Sealing the hairline cracks that were developing in the precast exterior required something of a novel approach. Shuffleton wanted to avoid painstaking hand sealing work, and he knew that the building's aesthetics also needed to be addressed, so he investigated a silicone exterior coating that he'd seen on other buildings in the area.

"The typical clear masonry sealers wouldn't bridge the small cracks that we'd observed at the Atlantis," Shuffleton said, "and they wouldn't have brought a significant improvement to the appearance. But we examined nearby structures that had solved this problem by using a unique elastomeric coating."

To address both the cracking and the appearance issues, Dow Corning's AllGuard Silicone Elastomeric Coating was chosen for all of the building's exterior walls.

"We observed several buildings in this area that have used AllGuard successfully to combat the same sorts of problems found at the Atlantis," said Mike Blair of Kenseal Construction Products, Baltimore, distributor for the Dow Corning materials. "Some of those structures were coated more than 10 years ago, and the silicone formulation has withstood the effects of the oceanside environment and countless freeze-thaw cycles very well. That kind of track record has been a key factor in the material's growing popularity in the Northeast."

Testing

Once the products were selected, the engineering team worked with general contractor Structural Maintenance Systems, Malvern, PA, investing about $75,000 on a mock-up and testing of all the weathersealing components to confirm their performance before proceeding.

"We started with one unit and completed the entire rehab on it: windows, sliding doors, caulking and exterior coating," said Rick Delargey, a principal at Structural Maintenance Systems.

"With Dow Corning's help, we then conducted a battery of tests to make sure that our materials and installation techniques produced a weatherproof system." Evaluating the mock-up included pull tests on the sealants and elastomer coating, as well as pressurized water testing to simulate severe environments.

"The entire weatherproofing system and the installation process were verified before we progressed to the rest of the building."

Delargey estimated that by the time the project is complete later this year, his crews will have installed approximately 25,000 lineal feet of 795 Silicone Building Sealant around doors and windows, and approximately 20,000 lineal feet of Dow Corning's 790 Silicone Building Sealant in concrete wall joints.

Perhaps the most apparent of the changes is the elastomer coating applied to the exterior.

"Aside from the deterioration, this building was just bare concrete," Shuffleton said. "Now the structure is a warm, appealing color, and the AllGuard has helped us seal up the building envelope without extensive exterior renovations."

After minor repairs to some 750 square feet of the vertical wall surface, structural maintenance crews applied two coats of the paint-like elastomer with rollers and brushes to cover approximately 125,000 square feet of the building's exterior. They used one standard color and one custom color for the project. The coating was applied without a primer, after a high-pressure wash.

As the work progresses, tests are performed regularly to spot-check sealant installation and coating thickness, and to confirm the overall integrity of the building envelope.

"Dow Corning is an integral part of the ongoing quality assurance program on this project," said Delargey. "It's pretty unusual to find a sealant manufacturer who repeatedly brings personnel to the job site to perform inspections and provide technical assistance, but it really helps us ensure that we end up with a watertight structure."

Dow Corning provides performance-enhancing solutions to serve the diverse needs of more than 25,000 customers worldwide. A global leader in silicon-based technology and innovation offering more than 7,000 products and services, Dow Corning is equally owned by The Dow Chemical Co. and Corning Inc. More than half of Dow Corning's annual sales are outside the United States.

For more information, contact Dow Corning Corp., P.O. Box 0994, Midland, MI 48686-0994; phone (989) 496-6000 or (800) 637-5377; fax (989) 496-8026; or visit www.dowcorning.com/construction. Reference no. P2083.