Waterproofing through the ages: From ancient Pyramids to modern day techniques

by arslan_ahmed | July 17, 2023 4:00 pm

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By Rockford Boyer, B. Arch. Sc., MBSc, BSS

Water is the source shaping the environment, connecting all living things, and is critical for all forms of life. However, despite its fundamental importance, water poses a significant threat to the long-term strength and durability of buildings. Its infiltration, whether in the form of bulk water or vapour, can have detrimental effects.

Traditionally, drying mechanisms were essential to address moisture within the enclosure system. When controlling moisture below ground, the only solution is to completely prevent its entry into the foundation system. Moisture ingress can cause various damaging functions that degrade the foundation system, including corrosion of reinforcement, freeze-thaw damage, and chemical attack. To ensure the longevity, operation, occupant comfort, maintenance, and sustainability of a building, it is necessary to use high-quality and high-performing waterproofing materials. This article explores the history of waterproofing materials and strategies over time. It also explores a highly advanced and one of the most durable waterproofing materials on the market today—polyurea.

A brief history

The origins of waterproofing and moisture management can be traced back more than 13,000 years ago. In the ancient world, the demand for skilled waterproofing was remarkably high, given its crucial role in various domains such as agriculture, construction, and transportation. This led to the emergence of the “waterproofing trade” as one of the most essential and sought-after professions, ranking behind masonry and carpentry.

Understanding the origins and history of waterproofing provides designers, architects, builders, and owners with real historical information and data on how previous groups developed and applied waterproofing solutions for their specific geological region and period. Historical records, buildings, and relics can provide valuable performance data, including nonperformance data, which can potentially increase the success rate of future waterproofing applications and materials. Previous examples of waterproofing performance, education and material used will ultimately elevate the designer’s knowledge about which solutions have the best potential for success. Manufacturers deal with scenarios like this every day when a new product is brought to market, designers often ask “how does this compare to competitive product which has been on the market for 10 years?” Those in the Paleolithic Period did not have the opportunity as today’s industry professionals do to have 1000s of years of waterproofing experience.

During the Paleolithic Age, mankind was transitioning into a “permanent resident” phase, rather than a nomadic hunter gatherer, and a moisture protection solution was needed for their agriculture surplus. Straw and clay were used as the typical solutions for grain surpluses; however, ceramics and bitumen vessels were developed to assist in the transportation of water and liquids. Bitumen emulsion on the underside of boats allowed for fishing, transportation, and longer land and sea explorations. These developments and advancements in waterproofing technology assisted in the progressions of the early day man and their transition to becoming a permanent resident.

In ancient Egypt, bitumen emulsion and dry reed fibres were used to waterproof the deep foundations of the great temples and pyramids. Archeological excavations have proven the effectiveness of ancient waterproofing, as the interior spaces of the pyramids remained dry, even during the annual floodings of the Nile River. During the Roman era, waterproofing techniques relied on sturdy masonry and concrete foundations and structures. Roman engineers incorporated volcanic ash, seawater, and lime in their concrete mix, to create a “pozzolanic” reaction that enhanced the concrete’s durability and resistance to water.

In Medieval Europe, security was of utmost importance. In situations where castles, forts, or towns lacked elevation or natural land features for protection, water-filled moats were employed as a defensive measure. Medieval engineers traditionally used lime plaster and/or a bitumen emulsion (sometimes mixed with horsehair) to waterproof these foundations from the water occupying moat. Another method utilized by engineers was the use of lead plates in conjunction with the bitumen emulsion to provide added protection against water ingress from the moat.

Bitumen was a viable waterproofing solution for foundations until the 1900s, when a more dependable “liquid” bitumen became commercially available. Rubber and resin waterproofing solutions dominated the industry until the mid-1900s, however, in pursuit of increasing the durability and quality of the waterproofing membrane, synthetic materials made their debut.

Waterproofing manufacturers in the 1960s and 1970s developed and implemented what they believed were the next generation of waterproofing solutions. Materials such as styrene butadiene, polyester varieties, acrylic, and acrylic emulsion were being used by the industry to enhance and increase application rates in below-grade waterproofing. Today, waterproofing commercial buildings typically consists of liquid- or sheet-applied materials that are derived from asphalt, bitumen, and plastic-type raw materials. Foundation waterproofing has advanced over thousands of years; however, construction materials and techniques have fundamentally changed since the laying of the first foundation stone of the great Pyramid of Giza.

Despite the vast knowledge and extensive history of waterproofing materials and techniques, there are still basic failures in waterproofing that persist daily. To mitigate the risk of in-situ waterproofing failures, it is crucial for the materials to address four key elements of operation: ease of full application, resistance to damage, monolithic protection, and a high level of chemical resistance. There are many variables that can lead to a waterproofing system failure, and removing some of these key problematic variables can contribute to a higher success rate in performance.

According to Building Diagnostics Associates, a building diagnostic firm in Florida, their findings through surveys and reviews revealed that approximately 60 to 70 per cent of failures can be attributed to poor construction, 20 to 25 per cent to inadequate design considerations, and the remaining 10 per cent to non-performing materials.¹

An insight on polyurea

With its exceptional durability and versatility, polyurea serves as a reliable solution that can be applied on-site, bridging the gap between subpar construction practices and insufficient design considerations. As a spray-applied membrane, it offers an efficient and effective means of achieving long-lasting waterproofing protection.

The construction industry has come a long way from the basic application of foundation waterproofing through brushes, buckets, and nose plugs. The modern waterproofing movement is directed toward resilient, free of volatile organic compounds (VOCs) and asphaltic, monolithic, high-performing resins, whether the advanced formulation is polyurethane or polyurea.

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Many polyurea’s in Canada have been tested to traditional “asphaltic” standards; however, it does not typically represent the true characteristics of the polyurea. To ensure the polyurea sold in Canada meets and exceeds the traditional waterproofing standards, testing protocols have been set up to ensure it outperforms its intended roll. It has been demonstrated polyurea can be unsupported when testing the resistance to hydrostatic pressure at various depths (other sheet goods, asphalt should be tested supported). Out of scope testing by leading building science/engineering firms have determined protection boards can be eliminated in front of the polyurea membranes due to their superior structural characteristics. Military branches around the world have also used polyurea for blast mitigation based on the products resistance to movement, abrasion, and impact.

Polyurea was developed more than 30 years ago by chemical engineers who formulated these resins to possess low VOCs, superior fire performance, a wide range of modulus options, and exceptional versatility and strength, surpassing the current leading waterproofing materials.

These waterproofing materials are applied by trained installers that utilize computerized plural component equipment to achieve a more uniform and effective system application. The computerized plural equipment (Figure 1) combines the isocyanates (A side) and resin blends (B side) at the tip of the nozzle to create an inert and durable urea-linkage waterproofing membrane. The initial curing of the waterproofing material happens within 20 seconds and the full cure occurs within the following few hours, resulting in a high tensile, high abrasion-resistant, and totally monolithic waterproofing membrane.

 The application of polyurea

Due to its ease of application, polyurea offers numerous possibilities on the jobsite. However, the most common applications of polyurea are for waterproofing and protecting vertical and horizontal concrete surfaces below-grade.

Blindside and positive side waterproofing using spray-applied polyurea has witnessed a surge in demand due to factors such as cost-effectiveness, speed, application quality, and effective resistance to damage during construction. However, the primary contributing factor is the application of polyurea to fresh concrete. The chemistry of the polyurea waterproofing allows application onto a damp substrate, whereas a polyurea/polyurethane blend could not.

Like any other waterproofing material, proper substrate preparation is imperative to the success of polyurea. As the saying goes, “the application is only as good as its substrate.” The surface of the substrate must be sound, clean, and free of oil, grease, wax, dirt, sealing compounds, or any contaminant which may act as a bond breaker.

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A concrete surface profile (CSP) reference guide on the quality and condition of the concrete substrates was created to assist building professionals, contractors, and applicators determine if the substrates require remediation prior to the application of the waterproofing (Figure 2). The CSP reference guide identifies a concrete condition ranging from CSP1 (smooth) to CSP10 (pitted), and should be reviewed prior to any application of a waterproofing membrane.

Application of a polyurea waterproofing membrane should be applied to concrete surfaces with a CSP between one to four, or the potential for blisters can occur (due to expanding gas). Primers should always be used on a concrete substrate to minimize the potential for waterproofing delamination and blistering. If it is not a CSP 1-4 concrete, it must be remediated to bring the concrete surface profile up to a CSP 1-4 prior to the application of a polyurea.

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Blindside waterproofing

Blindside waterproofing involves installing the drainage course and waterproofing membrane prior to placing the concrete vertical walls. In this process, the excavation is typically supported by soldier piles and lagging, soil nailing, shotcrete, or caisson walls. In addition, a drainage mat is applied overtop of the shoring wall, with the fleece side directly facing the wall. This configuration facilitates proper drainage and a reduced hydrostatic pressure.

When using a polyurea membrane, a fleece carrier sheet on the reverse side is typically used to receive the spray-applied waterproofing membrane (Figure 3). The spray-applied membrane is installed over the interior fleece, at a thickness specified by the manufacturer (typically 80 mils), although deeper foundations will require a thicker application. The added thickness of the polyurea waterproofing helps resist the higher water pressures at greater depths.

After detailing is complete and the monolithic waterproofing layer is applied, the concrete foundation wall is poured into place. Polyurea serves as an efficient solution to blindside waterproofing, expediting the installation process while delivering a seamless, resilient, and durable waterproofing layer.

Positive side waterproofing

Positive side waterproofing is an external system of waterproofing applied directly to the exterior surface of the structure being waterproofed (i.e. foundation wall). An effective positive side waterproofing system will protect the structure and its components from moisture ingress. Prior to the application of the polyurea waterproofing membrane, it is good practice to ensure the CSP aligns with the manufacturer’s written instructions.

After the primer is installed and cured as recommended, the polyurea waterproofing system can be sprayed directly to the exterior concrete face, creating a damage-resistant monolithic waterproof barrier around the structure. Typically, the use of drainage and protection boards placed over the top of the membrane have been used to protect the integrity of the membrane, and to relieve the hydrostatic pressure from the surrounding area. Recent testing has shown these drainage and protection boards can be eliminated due to the waterproofing’s structural characteristics.

Canada experiences numerous cold months, however, construction does not stop. Even in such conditions, polyurea membranes can be applied to substrate temperatures as low as -10 C (14 F). To meet energy requirements, insulation can be installed over the waterproofing membranes. Traditional exterior below-grade options could include closed-cell sprayed polyurethane foam (ccSPF), extruded polystyrene (XPS), expanded polystyrene (EPS), and mineral wool.

Conclusion

Whether it is historical structures such as the Great Pyramids of Giza, or addressing the Sunken Foundations of Gatineau, waterproofing materials and techniques play a vital role in preventing water infiltration into structures.

Water stands as the primary cause of building component degradation, making it crucial to prevent its entry into the assemblies, particularly below-grade ones. While adequate design and construction practices must be at the forefront, incorporating advanced materials such as polyurea can significantly enhance performance.

A high-performing waterproofing membrane should be easy to install, monolithic, damage-resistant, chemical-resistant, and capable of withstanding high levels of pressure—these are all attributes of polyurea.

Polyurea is a reliable and durable material suitable for various applications beyond blindside and positive side waterproofing, and adhering to manufacturer’s written instructions and following the guidance of the contractor can help ensure a long-lasting waterproofing system. Lastly, trained third-party installers equipped with state-of-the-art computerized application reactors can help minimize the risks associated with poor and inconsistent application.

Notes

¹ Learn more about water intrusion,
www.architectmagazine.com/technology/when-it-leaks-it-pours[5]

[6]Author

Rockford Boyer is an experienced building science leader at Elastochem, with more than 20 years of expertise in sustainable building design. He holds an undergraduate degree in civil engineering and architecture, as well as a masters in building science, and is a member of Passive House Canada and the Ontario Building Envelope Council (OBEC). He is also a part-time professor at Sheridan College, where he teaches in the architectural technology program, sharing his knowledge and expertise with future generations of architects and designers

Source URL: https://www.constructioncanada.net/waterproofing-through-the-ages/

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