Blindside Waterproofing: How to Select and Specify Pre-Applied Waterproofing Systems
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Blindside Waterproofing: How to Select and Specify Pre-Applied Waterproofing Systems
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Blindside Waterproofing: How to Select and Specify Pre-Applied Waterproofing Systems
- 1. Blindside Waterproofing Best Practices in Foundation Waterproofing for Difficult Sites
- 2. ⢠Family-owned and operated company ⢠1926 - First manufacturing plant in Elgin, IL ⢠Continued growth to bring regional manufacturing to all points in North America ⢠13 facilities throughout North America (3 in Canada) Who are we ?
- 3. Regional Manufacturing and Warehousing Facilities To Serve Your Individual Market Needs Seattle, WA Benicia, CA Pomona, CA Goodyear, AZ Fort Worth, TX Orlando, FL Cartersville, GA York, PA Lloydminster, ABSherwood Park, AB Danville, VA Kansas City, MO Denver, CO Hampshire, IL Milton, ON Boonville, MO
- 4. ⢠Expansion Joint Materials ⢠Concrete Restoration ⢠Construction Liquids ⢠Joint Sealants ⢠Decorative Concrete ⢠Building Envelope ⢠BLUE RIDGE FIBERBOARD ⢠Soundproofing and Insulation Board Meadowsâ Family of Products
- 5. AIA CES Provider Statement This program is registered with the AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product. Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.
- 6. Course Objectives Understand the fundamentals of why below-grade waterproofing Is essential and the types of waterproofing available. Examine basic facts of blindside and underslab waterproofing, as well as explore when to use blindside waterproofing as a waterproofing solution. Analyze the materials used in blindside waterproofing membranes. Review best practices for surface preparation and installation techniques of blindside waterproofing.
- 7. Blindside Waterproofing vs Traditional
- 8. Why is below-grade waterproofing essential and what types of waterproofing are available.
- 9. Moisture! Excessive moisture can cause significant damage to the foundation wall or lower level interior spaces. When the below grade portion of a building is not properly addressed with a waterproofing system, negative effects can be seen. Negative Effects Addressed by: - Interior waterproofing - External drain
- 10. Addressing the Problem ⢠Deeper the foundation â higher likelihood for water damage ⢠Water protection needs to happen on the outside or positive side DenseUrbanEnvironments
- 11. Main Objectives 1) Withstand hydrostatic pressure & crack bridging capabilities 2) Prevent vapour from entering the walls Effective Waterproofing Hydrostatic pressure is the constant force of water pressure against below-grade foundation walls. Water weighs 60 pounds per cubic foot, and during heavy rains the ground can become saturated with it. Even a well-constructed foundation wall can suffer water damage under those conditions.
- 12. Main Objectives â˘Prevent water vapor from entering the walls Effective Waterproofing Water can enter a foundation wall as a liquid through a crack, joint, or the concrete pores, or as vapor due to temperature and humidity variances between the interior of the structure and the exterior soil. If the structure is built on a slope and/or heavy rains or melting snow are concerns, it is always a good idea to be aware of how much water pressure might be present.
- 13. Choosing a Waterproofing System (positive, negative or integral) ⢠Choose a system that is designed to act as a barrier against water infiltration ⢠Must be applied evenly to all sides of a wall ⢠Needs to be continuous ⢠Areas need to withstand jobsite and environmental exposure ⢠Must be strong, flexible, and tear resistant ⢠Can accommodate movement
- 14. Positive-Side Waterproofing Positive-Side Waterproofing Advantages ⢠Most often used on new construction ⢠Best option when possible, protects structure from water damage before water even has a chance to penetrate ⢠Provides freeze-thaw protection ⢠Protects concrete against corrosive elements in groundwater and soil contaminates Disadvantages ⢠Difficult and expensive to repair (injection, etc) ⢠Needs extra attention during construction (GC, waterproofer, 3rd party inspector, manufacturer, etc)
- 15. Negative-Side/Interior Waterproofing Advantages ⢠Can be performed on existing construction, elevator pits, and tank liners ⢠Prevents water from entering the structure (but not the foundation wall) ⢠Repairs are easy (due to the exposed substrate) Disadvantages ⢠Lack of protection against freeze-thaw cycles ⢠Foundation is susceptible to water damage if not applied continuously Negative-Side Waterproofing
- 16. Free Space Capillary, micro-cracks in hydrated cement Choosing a Waterproofing System Integral Waterproofing Advantages ⢠Turns concrete into a water barrier ⢠Crystalline admixtures block the natural pores, capillaries, and microcracks ⢠Durable, easy application, reduced time and expenses Disadvantages ⢠Once the concrete breaks, so does the waterproofing barrier ⢠Joints and penetrations cannot be waterproofed Free space Filled with dendritic (needle-like) structures
- 17. Choosing a Waterproofing Material ⢠Cementitious ⢠Fluid-Applied Membrane ⢠Sheet Membrane ⢠Built-Up System ⢠Bentonite
- 18. Choosing a Waterproofing Material Cementitious Waterproofing Materials ⢠Effectiveness depends on the concrete itself, the site and applicators ⢠Mixed in with wet concrete on- site and react chemically with the concrete to add a water barrier to the mix ⢠Can be installed on the surface or can be integral within the mix ⢠Admixtures can be densifiers, water repellents or crystalline ⢠Limitation: These materials do not give and will not tolerate any joint or crack movement
- 19. Fluid-Applied Membrane ⢠An elastomeric coating for waterproofing Blindside applications ⢠Cold applied system using a spray system to impregnate a geo-textile ⢠fabric to create a durable, seamless membrane ⢠Limitation: Rely on applicator for thickness and the liquids can sometimes contain dangerous VOCs ⢠Need to purchase particular equipment in order to spray Choosing a Waterproofing Material
- 20. Sheet Membrane Choosing a Waterproofing Material ⢠Can be Self-adhering or mechanically fastened ⢠Requires skilled labour to install ⢠Critical to ensure proper detailing at the overlaps and penetrations of the membrane ⢠Advantages: Uniform thickness and repairs are easy ⢠IMPORTANT: Ensure the full manufacturersâ system is installed â all accessory products should be from one manufacturer to avoid any compatibility issues or warranty concerns
- 21. Bentonite Clay Membranes Choosing a Waterproofing Material ⢠Moisture resistant ⢠Ease of installation ⢠Limitations: Inability to test prior to installation; can be affected by certain chemicals found in the soil that may not allow it to swell when in contact with water ⢠Important: Bentonite is not an effective vapor retarder; however, it is often combined with sheets of geotextiles or plastic to increase its strength and provide a vapour barrier
- 22. Built-Up Waterproofing System Choosing a Waterproofing Material ⢠Time-intensive ⢠Requires a concrete primer, hot tar, and two or three felt sheets ⢠Provide good moisture resistance when applied properly ⢠Limitations: Not flexible and harmful VOCs can be released into the air ⢠NOTE: Built-up waterproofing systems have been around since the early 1900s and were the original blindside waterproofing solution
- 23. Examine basic facts of blindside and underslab waterproofing, as well as when to use blindside waterproofing as a waterproofing solution.
- 24. Blindside Waterproofing, is becoming an increasingly popular choice in new construction Increasingly popular in new construction and unconventional building sites Membrane needs to be able to withstand the weight and pressure of ongoing construction
- 25. Underslab Moisture Barriers The best blindside waterproofing material to use depends upon correctly specifying the underslab barrier ⢠High humidity levels in buildings leading to structural deterioration ⢠Moisture contribution to microbial growth, mildew and offensive odors ⢠Condensation on slab surfaces ⢠Flooring failures, ⢠De-bonding & blistering of coatings breakdown of floor covering adhesives ⢠Buckling of wood flooring and carpets
- 26. Analyze some materials used in blindside waterproofing membranes.
- 27. Drainage System Blindside Waterproofing Materials ⢠Act as the protection of the waterproofing membrane ⢠In many blindside situations, a composite drainage board is used ⢠Composite drainage board is fastened to the soil retention system prior to installation of the waterproofing membrane
- 28. Blindside Waterproofing Materials (attached or unattached) Materials currently used in blindside waterproofing include: ⢠Bentonite clay-based compounds and hydrophilic polymers laminated to Ethylene Interpolymer (EIP): ONLY thermoplastic materials recommended for below-grade waterproofing due to their ability to withstand water penetration and corrosive chemicals sometimes found in soil; ⢠High Density Polyethylene Based Homogenous (HDPE): Thermoplastic self-adhesive sheets coated with a layer of modified bentonite. (Not to be confused with thin HDPE sheet membranes, which are not recommended for below-grade waterproofing because of their inability to withstand water penetration) Thermoplastic HDPE sheets come in two types: chemical adhesion to the concrete slabs and foundation walls and forming a water-resistant barrier between the soil and concrete using the natural properties of bentonite; ⢠Geotextiles: Permeable fabrics can filter or drain water away from concrete foundation; woven, felt, or heat-bonded. They are used in conjunction with other waterproofing systems to strengthen the soil retention system, which helps to increase the effectiveness of other blindside waterproof applications; ⢠Self-adhering Sequenced-Butadiene-Styrene (SBS) laminated to a polyester fleece: Combine styrene and butadiene to form synthetic rubber; Excellent elongation properties, resistant to extreme weather conditions, and is extremely stable and durable. These types of materials adhere well to most substrates and installation can be done in a variety of ways; or, ⢠Butyl alloy laminated to thermoplastic polyolefin (TPO): TPO waterproof membranes are a thermoplastic rubber-like material coated with a polyisobutylene rubber. The adhesive on these sheets is made to be used below-grade in underslab waterproofing because it can withstand construction traffic above-grade.
- 29. Blindside Waterproofing Membranes (when to use them?) 7 criteria to evaluate a siteâs waterproofing needs 1. Soil condition 2. Hydrostatic pressure 3. Water table 4. Substrate stability 5. Building occupancy 6. Construction method 7. Site access
- 30. Betonite Clay Membranes Blindside Waterproofing Membranes Requires adequate hydration at the right time to effectively work ⢠Effective water sealant because of their natural chemical properties, high tensile strength and ability to withstand high levels of hydrostatic pressure ⢠Benefits: Works best in new construction for below-grade waterproofing
- 31. Sheet Waterproofing Blindside Waterproofing Membranes ⢠Self-adhering and cold-applied; limited release of harmful chemicals; Increased tensile strength and elongation ⢠Thicker and less sensitive to changes in temperature ⢠Bond with most surfaces and create a mechanical bond with the concrete ⢠NOTE: key differences between self- adhering blindside products and mechanically fastened products
- 34. Challenges: There were zero property lines, limited site access, and the waterproofing system could not allow any water infiltration before concrete was poured. A huge rainstorm happened after the first day of waterproofing installation, but everything remained intact.
- 35. Review best practices for surface preparation and installation techniques of blindside waterproofing.
- 36. Even the best waterproofing systems can experience failure: - substrate! - seams are not sealed completely Best Practices for Installation
- 37. Fasteners - Are the correct fasteners being used? - Do they need to be sealed? - Correct placement â one foot apart? Across the top or down the sheet? Best Practices for Installation
- 38. Weak Points Sheet membranes are highly effective at keeping water out, but the systems, weak points are the overlaps that need to be addressed. 3 Ways To Seal Seams 1. Taping 2. Heat-fusing 3. Self-sealing factory edge Test - RAIN Best Practices for Installation
- 39. Transitions Seam transitions are most vulnerable between horizontal and vertical planes. Welding, flexible sheets at the corners, tapes, and liquid components will create a better angle that is impermeable to water than adhesives or bentonite flaps alone. Best Practices for Installation
- 40. After Membrane Installation ⢠Clean the membrane with a vacuum and blower â the membrane must be dry and free of any standing water to ensure the concrete can form a bond. ⢠Inspect the membrane for damages prior to the pour ⢠Recommendation: Train all the crewâŚ. not just the foremen, on the installation details Best Practices for Installation
- 41. Project Considerations ⢠Due to the large variety of jobsite conditions, including environmental conditions and delays in construction, various membrane manufacturers offer a variety of materials to address jobsite uncertainty. ⢠It is very important to review all aspects of the project and the material being selected to ensure success in the project. Best Practices for Installation
- 42. Conclusion As construction of new buildings and renovations of existing ones becomes more complex, architects and builders are challenged with new ways of addressing water infiltration. Old methods of waterproofing are giving way to more advanced systems. Difficult sites that used to be only accessible for negative-side waterproofing can now be addressed from the outside-in using blindside waterproofing applications. Understanding what options are available and how best to apply blindside membranes will help the construction industry build better structures that are protected from water damage for years to come.
- 43. Thank you for your time and interest in the course, âBlindside Waterproofing: Best Practices in Foundation Waterproofing for Difficult Sites.â Thank You Contact Information: Stacey Bogdanow sbogdanow@wrmeadows.com
- 44. This concludes the AIA portion of this presentation. Visit wrmeadows.com or call 800-342-5976. BIM Models CAD Details Guide Specs #wrmeadows info@wrmeadows.com
Editor's Notes
- Welcome to, Blindside Waterproofing: Best Practices in Foundation Waterproofing for Difficult Sites, presented by Stacey Bogdanow with W.R. Meadows Canada. ( I am the outside sales rep that looks after ½ of Toronto & eastern Ontario (not Ottawa))
- WR MEADOWS is a familyâŚâŚ.WR MEADOWS was founded in 1926 & manufactured one product â the Asphalt Expansion Joint. The Plant was in Elgin, IL
- This is a 1 hour AIA accredited presentation - Earn an AIA credit (1 unit credit) Â Â
- Today I will be talking about: Understand the fundamentals of why below-grade waterproofing is essential and the types of waterproofing available. Examine blindside and underslab waterproofing, as well as explore when to use blindside waterproofing as a waterproofing solution. Analyze the materials used in blindside waterproofing membranes. Review why surface preparation is so important and also review basic practices of installation techniques of blindside waterproofing.
- Blindside waterproofing is a newer approach to below-grade waterproofing on job sites, where traditional waterproofing is not possible. Traditional waterproofing (which can also be called Open Cut) is where, a foundation wall is poured and concrete is given ample time to cure, prior to waterproofing. Blindside is where, a soil retention system is required to keep the soil out of the hole, (wood lagging, caisson walls, shotcrete walls, etc)âŚ.then install waterproofing onto the soil retention system, then pour the foundation wall up against the waterproofing membrane. Blindside systems are used on a job site where the foundation is below the water table or under a great deal of hydrostatic pressure. (Height, Weight & Density of water pressing up against the structureâŚ.. The greater the Height, Weight & Density, the greater the pressure⌠looking for a crack or area that was not detailed correctly) Blindside waterproofing is also, a solution for zero lot lines and sites with limited access. Utilize âŚ. Itâs important to understand which materials and techniques to use in blindside waterproofing applications to ensure a lasting waterproofing system.
- We will discuss the fundamentals of why below-grade waterproofing is essential and the types of waterproofing available.
- Moisture is the reason why there are so many different types of waterproofing products on the marketâŚâŚ Excessive moisture can cause significant damage to the foundation wall or lower level interior spaces in large, urban, commercial buildings. When the below grade portion of a building is not properly addressed with a waterproofing system, negative effects can be seen. Negative effects, can be addressed by interior waterproofing, which does not stop the external damage or water pressure. Sometimes, installing an external drain (weeping tiles or a system that pumps water away from the structure) or grading soil away from the building can help, but these are not always options depending on the building location. If you ask any manufacturer, it is always best to waterproof on the positive side, of the below grade structure (or the wet side of the wall)âŚbasically the side where the water is coming from
- Dense urban environments â buildings have more floors below grade than ever before, which makes waterproofing difficult. In urban areas, buildings are located close to one another, that can have multi-level parking garages, meeting spaces in a hotel, finished basement in a home, etc The deeper the foundation, the higher the chance, for water damage. The water protection needs to happen on the outside (or the positive side), but in an urban environment, that becomes difficult because of the zero lot lines.
- Effective waterproofing will accomplish three main objectives: Withstand hydrostatic pressure Prevent vapour from entering the walls Hydrostatic pressure is the constant force of water pressure against below-grade foundation walls. Water weighs 60 pounds per cubic foot, and during heavy rains the ground can become saturated with it. Imagine thousands of pounds of pressure pushing against the wall â constantly. (high water table will create a great amount of height, weight and density of water, pressing up against the foundation wall, creating a strong water pressure). Even a well-constructed foundation wall can suffer water damage under those conditions.
- Water can enter a foundation wall as a liquid through a crack, joint, concrete pores, or as vapour due to temperature and humidity between the interior of the structure and the exterior soil. (what we understand about vapour, it will naturally go from an area of high vapour pressure to an area of low vapour pressure) In the soil â the temp is 13 degrees C & 100% relative humidity (From those 2 numbers the vapour pressure is 0.214 â HIGH) & the inside of the structure usually has an average temp of 20 degrees C and relative humidity of 30% (from those 2 numbers the vapour pressure is calculated to be 0.104 â Low)âŚ.. So now we have a natural vapour drive from the soil, through the concrete (because we know concrete is not a good vapour barrier â it is permeable) & into the structure If the structure is built on a slope or heavy rains or melting snow could be a concern, these also could contribute to increase pressures. Â
- There are three ways to install waterproofing: positive side, negative side, and integral. Each method has advantages and disadvantages - the system must be designed to act as a barrier against water entering into the structure. The waterproofing system used, needs to be applied evenly to all sides of a wall â no holes, gaps, or thin areas â and, it needs to be continuous. The waterproofing system needs to be durable, strong, flexible and tear-resistant throughout construction and able to withstand UV exposure while the rest of a buildingâs construction is completed. The waterproofing system should be able to accommodate movement (the projects movement) and provide the appropriate crack-bridging capability for the project, should cracks occur. Â
- Positive-side waterproofing occurs on the outside, or the same side as the water source (wet side of the wall). It is most often used in new construction. It is considered the best option when possible because it protects the structure from potential water damage before water even has a chance to penetrate. Positive-side provides freeze-thaw protection and protects the concrete against corrosive elements in groundwater and soil contaminants. Corrosive elements in water can consist of bicarbonate, calcium, magnesium, nitrate, sodium, and phosphate. Chemical concentrations can also depend on where the structure is located; industrial, agriculture, and waste disposal can leave toxic chemicals in the water that cannot be filtered out naturally in the ground. Full protection against corrosive elements in the groundwater depends on the material and chemicals. Â This would be dependent on the material and the chemicals. Positive-side waterproofing disadvantages. if repairs are needed, the process is difficult and expensive during construction, positive-side waterproofing relies on extra attention from the project team (GC, waterproofer, 3rd party inspector, manufacturer, etc)
- Negative-side, or interior(or dry side of the wall), waterproofing is usually performed on existing construction, elevator pits, and tank liners., etc Negative-side waterproofing prevents water from entering the structure, but not the foundation wall. Repairs are easy because the substrate is exposed. Disadvantages including a lack of protection against freeze-thaw cycles (example â if the wall is a block wall & it is hollow â the water is able to enter, expand and may damage the wall further) Even if not block wall - water is allowed to enter in the concrete â possible deterioration of the concrete from water exposure and corrosion of the reinforcing steel. With positive side waterproofing you eliminate the exposure completely
- Integral waterproofing turns the concrete into a water barrier. The barrier is created when a chemical reaction occurs as water penetrates the concrete. Crystalline admixtures block the natural pores, capillaries, and microcracks. Intregral waterproofing forms long, narrow crystals that continue to grow throughout the concrete as long as moisture is present. When the concrete dries, these crystals lie dormant until theyâre reactivated by water. This self-sealing waterproofing system is durable, easy application process, and reduces time and expenses for the project. A disadvantage is that once the concrete breaks, so does the waterproofing barrier (what if the cracks are larger than a microcrack?). Also, joints and penetrations are unable to be waterproofed.
- Waterproofing materials - cementitious, fluid-applied, sheet, built-up system, and bentonite are a few materials available. Many materials are manufacturered because there is not one membrane for all applications. So it is important to consider - the type of project and where the waterproofing will be applied.Â
- The effectiveness of cementitious waterproofing depends on the concrete itself and the site. These materials are mixed in with wet concrete on-site and react chemically with the concrete. Cementitious materials can be installed on the surface or can be integral within the mix. Admixtures can be densifiers, water repellents or crystalline. A limitation of specifying cementitious materials â specific to projects that need flexibility â these materials do not give and will not tolerate any joint or crack movement.
- Typically, these membranes require skilled labour to install and it is critical to ensure proper detailing at the overlaps and penetrations of the membrane. Advantage - uniform thickness and repairs are easy with this material. It is important to use the manufacturersâ complete system when waterproofing â meaning all accessory products should be from one manufacturer to avoid any compatibility issues and avoid compromising the warranty.
- Bentonite clay membrane waterproofing has been popular in many situations due to its moisture resistance and ease of installation. Sodium bentonite, has natural chemical properties allowing it to expand up to 15 times its original size when it reacts with water to waterproof the structure. Limitations - sheets are not sealed together until the wall experiences hydrostatic pressure when it is in place and backfilled. Also, bentonite can be affected by certain chemicals found in the soil that may not allow it to swell when in contact with water. Most foundation walls also need a high level of hydrostatic pressure to complete the bonding process, but it is not an appropriate choice for walls that will not experience a high level of hydrostatic pressure. Bentonite is not an effective vapor retarder; however, it is often combined with sheets of geotextiles or plastic to increase its strength and provide a vapour barrier.
- The built-up waterproofing system is time-intensive and requires a concrete primer, hot tar, and two or three felt sheets. Built-up systems provide good moisture resistance when applied properly, but are not flexible and harmful VOCs can be released into the air. However, built-up systems can be cold applied, and some cold-applied systems do not release VOCs. Built-up waterproofing systems have been around since the early 1900s and were the original blindside waterproofing solution.
- Now lets examine the basic facts of blindside and underslab waterproofing as well as explore when to use blindside waterproofing as a waterproofing solution.
- Blindside waterproofing is becoming an increasingly popular choice in new construction and unconventional building sites. New builds are more complex, energy codes are stricter, and there is less room for a large excavation site in dense environments. Although it can be more expensive than a traditional positive-side application, blindside waterproofing might be the simpler, and even the only, way to achieve protection from water infiltration on difficult sites. In a blindside application, the membrane needs to be able to withstand the weight and pressure of ongoing construction, and the presence of water can be a concern depending on the material or how the concrete is poured âŚ.. That is why dewatering systems maybe needed & preinstallation meetings regarding the concrete pour, etcâŚ..Careful planning and attention to detail are necessary because installing the waterproofing against a soil retention system instead of concrete can become complex and prone to errors if done incorrectly.
- Underslab moisture barriers are used in conjunction with blindside applications and sometimes are the same material. Protecting a structure against water infiltration should begin with an understanding of site-specific needs, such as building location and use and groundwater condition. The best blindside waterproofing material to use depends upon correctly specifying the underslab barrier. Water infiltration is the single largest factor in limiting the useful service life of a structure and can lead to negative health consequences for occupants. Effective underslab moisture barriers are designed to greatly minimize: High humidity levels in buildings leading to structural deterioration, Mildew, odors, Condensation on slab surfaces, Flooring failures, De-bonding & blistering of coatings breakdown of floor covering adhesives, and Buckling of wood flooring and carpets.
- Now that you understand the different types of blindside waterproof membranes, the following discussion will analyze the specific materials used in the membranes. The success of blindside waterproofing depends on using the right materials for the job. There are many choices of materials to use in blindside waterproofing. Some are tried and tested over the years, some are newer â within the last 15 years or so â and some practices are outdated and hardly used due to either improved technology or updated energy code requirements.
- For a waterproofing system to be effective, most waterproofing membranes are used in conjunction with a drainage system, which acts both as a drainage medium and as protection of the waterproofing membrane. Drainage systems can be in the form of on-site draining fill, but in many blindside situations, a composite drainage board is used. The composite drainage board is fastened to the soil retention system prior to the installation of the waterproofing membrane. When used for proper drainage, it is important that this drainage layer be integrated with the overall site drainage system to redirect the water away from the structure.
- Blindside membranes are considered to be either attached or unattached. The membrane will adhere directly to the concrete (attached) or they contain a granular bentonite compound or a hydrophilic polymer that binds with the concrete itself (unattached). Traditional below-grade waterproofing solutions relied on a single-layer sheet membrane. Modified bitumens use advanced technology to improve the waterproof barrier. The most common modified bitumens are analyzed below. Materials currently used in blindside waterproofing include: Bentonite clay-based compounds and hydrophilic polymers laminated to Ethylene Interpolymer (EIP): ONLY thermoplastic materials recommended for below-grade waterproofing due to their ability to withstand water penetration and corrosive chemicals sometimes found in soil; High Density Polyethylene Based Homogenous (HDPE): Thermoplastic self-adhesive sheets coated with a layer of modified bentonite. (Not to be confused with thin HDPE sheet membranes, which are not recommended for below-grade waterproofing because of their inability to withstand water penetration) Thermoplastic HDPE sheets come in two types: chemical adhesion to the concrete slabs and foundation walls and forming a water-resistant barrier between the soil and concrete using the natural properties of bentonite; Geotextiles: Permeable fabrics can filter or drain water away from concrete foundation; woven, felt, or heat-bonded. They are used in conjunction with other waterproofing systems to strengthen the soil retention system, which helps to increase the effectiveness of other blindside waterproof applications; Self-adhering Sequenced-Butadiene-Styrene (SBS) laminated to a polyester fleece: Combine styrene and butadiene to form synthetic rubber; Excellent elongation properties, resistant to extreme weather conditions, and is extremely stable and durable. These types of materials adhere well to most substrates and installation can be done in a variety of ways; or, Butyl alloy laminated to thermoplastic polyolefin (TPO): TPO waterproof membranes are a thermoplastic rubber-like material coated with a polyisobutylene rubber. The adhesive on these sheets is made to be used below-grade in underslab waterproofing because it can withstand construction traffic above-grade.
- Builders can choose between different membrane materials for blindside waterproofing systems. Although we have covered a basic overview of different waterproofing membranes, next we will discuss the characteristics of the materials used in below-grade waterproofing and when to use them. The purpose of below-grade waterproofing is to prevent water and vapor infiltration and protect structural integrity. According to The Manual of Below-Grade Waterproofing Systems, there are six criteria to evaluate a siteâs waterproofing needs. They are: Soil condition Hydrostatic pressure Water table location Substrate stability Building occupancy Construction method In addition, now that more buildings are being constructed close together and with stricter energy code requirements, site access can be considered a sixth criteria. Even if traditional positive-side waterproofing is desirable, there may be situations where it is not possible due to site access. In these situations, blindside waterproofing can be the only solution to achieving protection from water infiltration on the buildingâs exterior.
- As previously discussed, bentonite clay membranes are an effective water sealant because of their natural chemical properties. They also have a high tensile strength and can withstand high levels of hydrostatic pressure. However, if the clay absorbs any water during installation, it will expand prematurely and lose its strength. The soil retention system is the primary line of defense for ensuring bentonite stays confined against foundation walls until the concrete is poured. Because soil retention systems can shift and weaken, some bentonite applications use multi-layered sheets of geotextiles or plastics between the clay. Bentonite requires adequate hydration at the right time to effectively work. Once applied, the bentonite needs completely saturated with high hydrostatic pressure to active the clay molecules. This needs to happen immediately after the clay mixture is installed and backfilled, and the bentonite needs to be well-confined. The risk is the clay leaking out and away from the foundation or cracking the concrete slab. Â Bentonite clay membranes work best in new construction for below-grade waterproofing. Despite hydration requirements during installation, membranes can still be installed on green or damp surfaces. It can be used in horizontal and vertical applications. A water test may be required prior to installation.
- Unlike traditional sheet waterproofing that called for hot asphalt and manual sealants, modern sheet waterproofing membranes tend to be self-adhering and cold-applied. These advancements limit the release of harmful chemicals and also increase tensile strength and elongation. The sheets contain polymers combined with asphalt, which are then attached to the polyethylene sheet. The result is a waterproofing system that is thicker and less sensitive to changes in temperature. Sheet membranes will bond with most surfaces and create a mechanical bond with the concrete. In blindside waterproofing, sheet membranes are used in vertical applications. Each manufacturer has guidelines for installing blindside, below-grade sheet waterproofing. Check on the surface temperature requirements and when concrete should be poured. Note that standard peel and stick sheet membranes are not used for blindside waterproofing. Key Differences: ¡Self-adhering blindside products are a type of self-adhesive blindside membrane that is applied to the backside of a previously installed drainage board on a soil retention system and consists of a bituminous layer and geotextile fabric. ¡Mechanically fastened products are not self-adhesive but have a patented core system along with the bituminous layer and fabric. This product is mechanically fastened and in some situations does not need the drainage board. It is much more of a durable product.
- The following case studies include healthcare, commercial office space, and rapid transport infrastructure. Blindside waterproofing was a successful solution to challenging waterproofing conditions, which ranged from additions to an existing structure with groundwater issues, deep excavation and waterproofing between retaining walls, and the nationâs largest underground waterproofing project.
- Finally, in this final section, the course will review best practices for surface preparation and installation techniques of blindside waterproofing.
- Even the best waterproofing systems can experience failure if seams are not sealed completely, fasteners are not applied at proper intervals, or concrete is poured in a way that could damage the membrane or soil retention system. Installation will vary depending on the type of materials and specific site requirements. SMOOTH, SOUND substrate
- Membranes are typically folded over themselves at the top of the soil retention system and tacked into place, or they are mechanically fastened to a pre-installed factory edge. Seams can be either roll pressed or mechanically fastened with mastic over the fasteners. Membranes may also be required to tie-in to additional waterproofing materials being used on the project. For example, if the concrete deck is to be waterproofed, both the detailing and compatibility of these materials are essential to the success of the system.
- Sheet membranes are highly effective at keeping water out, but the system weak points are the overlaps that need to be addressed. There are three ways to seal seams: taping, heat-fusing, and a self-sealing factory edge. Taped seams can more easily resist shrinkage that is common with HDPE and improve the seamâs integrity, however, variations in installation also leave room for gaps. Heat-fused seams provide the best results for a watertight seal. They resist differential movement between the concrete and substrate, but heat-fusing is more expensive, can only be used on certain types of materials, and is not used very often.
- Seam transitions are most vulnerable between horizontal and vertical planes. Seams can become tented when bent over corner angles due to the stiffness in sheet membranes. Corner seams are also susceptible to ruptures or disbonding. Tight corners can be almost impossible to achieve using only one piece of sheet membrane. In these situations, use a combination approach to seal joints and seams. Welding, flexible sheets at the corners, tapes, and liquid components will create a better angle that is impermeable to water than adhesives or bentonite flaps alone.
- After the membrane is installed, itâs important to: Clean the membrane with vacuum and blower. The membrane must be dry and free of any standing water to ensure the concrete can form a watertight bond. Inspect the membrane for surface consistency and to ensure nothing was damaged. Itâs recommended to train all laborers, not just the foremen, on the installation details, especially as it concerns overlaps, transition points, and planes as these are areas that can fracture the whole system. It is considered a best practice to use one manufacturersâ product throughout the whole waterproofing process. This ensures compatibility between materials, installation guides, and warranties.
- Due to the large variety of jobsite conditions, including environmental conditions and delays in construction, various membrane manufacturers offer a variety of materials to address jobsite uncertainty. Low temperature formulations, and also materials that accommodate a longer exposure to UV during the construction stage, are a few materials available. It is very important to review all aspects of the project and the material being selected to ensure success in the project.
- As construction of new buildings and remediation of existing ones becomes more complex, architects and builders are challenged with new and evolving means of addressing water infiltration. Old methods of waterproofing are giving way to more advanced systems. Difficult sites that used to be only accessible for negative-side or integral waterproofing can now be protected from the outside-in using blindside waterproofing applications. Understanding what options are available and how best to apply blindside membranes will help the construction industry build better structures that are protected from water damage for years to come.
- Thank you for your time and interest in the course, âBlindside Waterproofing: Best Practices in Foundation Waterproofing for Difficult Sites.â Please contact WR Meadows directly for any questions related to the materials covered in this course. CONTACT INFO: XXXX
- Thank you for your time and interest in the course, âBlindside Waterproofing: Best Practices in Foundation Waterproofing for Difficult Sites.â Please contact WR Meadows directly for any questions related to the materials covered in this course. CONTACT INFO: XXXX