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The One Percent of Cost That Can Become 90 Percent of Trouble

The Economic and Practical Benefits of Standardization for Building Seals and Sealants

by Thomas F. O'Connor

The scope and activities of Committee C24 on Building Seals and Sealants includes materials and systems that amount to approximately one percent of the construction cost of a typical large building project. However, when a building develops water leaks, these materials and systems can become 90 percent of the problem, with remediation and damage correction costing many times the installation cost (see Figure 1). C24 members have recognized the significant role of standard specifications and guides in helping reduce the occurrence of such problems, and also their usefulness as tools to educate the designer, user, and installer.

Without construction standards, the growth of national design and construction firms would probably not have occurred, as we know it today. As the United States grew and prospered in the early part of the 20th century, the regional variety of sizes and shapes of construction products (e.g. brick, lumber, and fasteners) would surely have hampered the growth of a national construction industry. However it was early recognized, by at least the burgeoning railroad industry, that national standards were needed to achieve uniformity of sizes, shapes, and dimensions, from region to region, to make economic sense for continued growth. Having to manufacture, handle, or stock multiple sizes and shapes to respond to a particular region was not economically justifiable. As a result, the formation of standards writing societies has played a major role in the growth and prosperity of the construction industry. Committee C24 on Building Seals and Sealants is proud to have contributed to this effort.

Building sealants are used to seal many types of joints during the construction and maintenance of buildings. Often a sealant joint becomes the sole means of preventing the entry of unwanted air and water into a building. The need for industry-wide sealant standards was recognized in the mid 1950s. This was coincident with the development of modern glass and aluminum curtain walls when traditional putty type materials were found to be performing inadequately. ASTM Committee C24 on Building Seals and Sealants was established in 1959 to develop standards for emerging high-performance sealing materials. C24’s first standards, for caulking, had been originally developed by Committee D01 on Paint and Related Coatings, Materials, and Applications and were transferred to C24.

Presently, C24 has over 220 members from at least 30 states and five countries drawn from a cross-section of the international construction industry including architects, engineers, contractors, specialty consultants, manufacturers, suppliers, government representatives, and installers.

Since its founding, C24 has developed over 100 standards and, significantly, one-third of these standards are specifications and guides. A large part of the users of C24 standards is building professionals such as architects, engineers, and code officials. They rely on and include specifications and guides in their documents to ensure proper use of building seals and sealants. Presently C24 has about two dozen standards in various stages of development.

C24 was formed initially to develop building sealant standards, however, it was recognized soon after its formation that its scope and activities should enlarge and they currently include the following general topics described in the balance of this article.

• Weatherproofing sealants for buildings;
• Structural silicone sealants for curtain walls and windows;
• Glazing gaskets and accessories;
• Building deck and foundation waterproofing;
• Plumbing and sewer pipe couplings and gaskets; and
• Representation to the International Organization for Standardization.

Weatherproofing Sealants

The building industry relies heavily on the performance of sealants. Sealants are used to seal joints between materials on the facades and other areas of buildings. Frequently the sealant joint is the sole means of preventing water intrusion into the building’s construction or its interior spaces. The need for high-performance sealants and standards became readily apparent in the mid-1950s with the failure of traditional putty-based caulking materials used with newly developed metal and glass curtain walls (see Figure 2). Committee C24 was formed to develop these sealant standards. Early on, in conjunction with the then-U.S. National Bureau of Standards (now the National Institute of Standards and Technology), and using test methods developed by its scientist Arthur Hockman, Specification C 920 for Elastomeric Joint Sealants was developed for chemically curing sealants. This standard has been recognized worldwide for its quality. C 920 is a living document that has been continually updated to include new materials and advances in technology. In conjunction with C 920, two standards — C 1193, Guide for Use of Joint Sealants and C 1472, Guide for Calculating Movement and Other Effects When Establishing Sealant Joint Width — provide design professionals excellent tools to enable them to properly use weatherproofing sealants.

Structural Silicone Sealants

Early in the 1970s a new technology, structural sealant glazing, was developed to adhere glass to metal framing systems using a sealant (see Figure 3). During the 1980s and ’90s it was generally recognized that at least one-third of building curtain walls and windows were installed using this technology. C24 began developing standards for this technology with its potential high liability of relying on the adhesion of a sealant to retain glazing materials while using no mechanical fasteners. Currently only a silicone sealant is acceptable for structural glazing of materials. Among others, C24 has written Specifications C 1184 for Structural Silicone Sealants and C 1369 for Secondary Edge Sealants for Structurally Glazed Insulating Glass Units; these are installed in structural sealant applications. C24 has also developed Guide C 1401 for Structural Sealant Glazing which, at 55 pages in length, is recognized as the most comprehensive document available that describes this glazing technology. After construction, the inspection and maintenance of these systems is equally important to limit potential liability. C24 has developed three guides: C 1392 for Evaluating Failure of Structural Sealant Glazing, C 1394 for In-Situ Structural Silicone Glazing Evaluation, and C 1487 for Remedying Structural Silicone Glazing.

Glazing Gaskets and Accessories

The development of modern curtain wall and window systems identified a need for quality standards for glazing gaskets and accessories. Among the first specifications developed by C24 was C 509 in 1963 for Elastomeric Cellular Preformed Gasket and Sealing Material, which was followed shortly thereafter by C 864 for Dense Elastomeric Compression Seal Gaskets, Setting Blocks, and Spacers. Prior to their development, design professionals and others had been unable to discern the quality of gaskets — and deficient durability was fairly common. These two specifications established minimum quality levels for the first time and are still the standards of choice for specifying quality glazing gaskets and accessories. Additionally, several standards were also developed for lock-strip gasket glazing. This technology is not commonly used today by the construction industry; however, the standards are still important for the remediation and maintenance of these glazing systems. Lastly, with the development of silicone rubber technology, Specification C 1115 for Dense Elastomeric Silicone Rubber Gaskets and Accessories was developed.

Building Deck and Foundation Waterproofing

New waterproofing materials became available shortly after the founding of C24, however their early use included notable failures. These failures were not so much due to the materials themselves, but more to a lack of system information for proper design and application of the waterproofing membranes. Recognizing a need, C24 convened a meeting in the late 1960s with approximately 200 in attendance to discuss developing comprehensive guides and practices for the design and application of waterproofing systems for the waterproofing industry. Since that time, C24 has developed four guides and two specifications with related test methods for proper specification, design, and application of liquid-applied and bituminous membrane systems (See Figure 4).

Plumbing and Sewer Pipe Couplings and Gaskets

Specification C 564 for Rubber Gaskets for Cast Iron Soil Pipe and Fittings was first published in 1965. Approximately 20 years ago a need was identified to recognize other types of materials and coupling systems to join drain, waste and vent piping for plumbing systems. Although this activity had a difficult start, the subcommittee members, with a lot of hard work, achieved consensus and have produced seven specifications for a variety of couplings using different materials for differing applications. This subcommittee’s work is an excellent example of the value and worth of the ASTM consensus standards development process.

ISO Participation

For over 25 years C24 has actively participated in the development of ISO (International Organization for Standardization) standards. The committee plays a preeminent role in the ISO process by housing the U.S. Techical Advisory Group to ISO Technical Committee 59 on Building Construction’s Subcommittee 8 on Jointing Products. C24’s involvement has ensured that U.S. sealant products are represented in ISO standards and that appropriate ASTM standards are proposed as a basis for the development of ISO standards. With the globalization of the construction industry, ISO participation has become a necessity and not a luxury.

Work in Progress

As indicated earlier, approximately two dozen standards, ranging from sealant mildew resistance to waterproofing drainage issues, are currently under development by C24. Most significantly, a need has been recognized by C24 members for updating weathering standards to real-world weathering mechanisms.

Currently, several sealant and waterproofing test methods use a variety of artificial weathering procedures, which have a poor relationship to actual weathering conditions and provide inconsistent and misleading predictions of potential durability. C24 members, in conjunction with the international scientific community, have for several years been participating in a worldwide program of sealant testing under actual weathering conditions at sites located around the world. This testing will be correlated with artificial weathering in the laboratory to arrive at sets of data that will permit reasonable predictions of sealant durability for various climatic conditions. For example, 500 hours of exposure in a laboratory-weathering device may be equivalent to a year’s exposure in northern Michigan but only a summer’s worth in St. Louis, Mo. It is anticipated that soon the industry will be able to adequately test sealants and waterproofing in the laboratory, resulting in reasonable predictions for durability. A specifier or user could then select products based on local climactic conditions and planned durability or service life. Today that is not possible objectively.

C24’s Contribution

C24 is continuing to establish a strong base of standards as it moves into its 45th year. These standards are resulting in better performing sealant, waterproofing, glazing, and pipe gasket and coupling products and systems. C24’s activities result in standards that direct the construction industry toward better quality materials, systems, and appropriate design and installation information and practices. The creation of these standards results in the economic benefit of less material and system failure, less leakage and resultant damage, and the creation of a level playing field. With continuing C24 standards development and industry education the one percent of a construction cost will truly become one percent of a building owner’s problem. //

Copyright 2003, ASTM

Thomas F. O’Connor, FAIA, FASTM, is an architect and vice president and director of the Building Technology Studio at SmithGroup. O’Connor’s focus is the development of enclosure systems including curtain walls, skylights, and waterproofing. He is a past chairman of ASTM Committee C24.

The following illustrates the range of materials and products that is within the scope of C24.

Sealant Materials:

• Chemically curing silicones, polyurethanes, and polysulfides
• Water-based latexes and acrylics
• Solvent based butyls and acrylics
• Hot-applied sealants
• Oil- and resin-base caulking compounds
• Preformed butyl tape sealants
• Precured, molded, and extruded silicone shapes
• Foamed-in-place polyurethanes
• Precompressed polyurethane based foams

Glazing Gaskets and Accessories:

• Cellular ethylene-propylene-diene terpolymer (EPDM) and neoprene rubber gaskets
• Dense EPDM and neoprene rubber gaskets
• Lock-strip gaskets
• Dense silicone rubber gaskets

Waterproofing Membranes:

• Liquid-applied urethanes
• Built-up bituminous
Pipe Couplings and Gaskets
• Rubber gaskets
• Thermoplastic elastomeric gaskets
• Flexible polyvinyl chloride gaskets
• Flexible transition couplings
• Shielded couplings
• Mechanical couplings