When selecting a waterproofing system, conservatism is the watchword. If leaks appear after the building is completed, the cost of excavation for repairs — even minor repairs — typically far exceeds the initial cost of the waterproofing system. Remember, as a designer you only have one chance to do it right. Research and due diligence are required to ensure that the right system is specified and all waterproofing issues are properly addressed. Site-specific issues and building requirements also necessitate proper consideration.
Components of the Waterproofing System
Waterproofing is the formation of an impervious barrier that is designed to prevent water from entering or exiting from various sections of the building structure. The waterproofing system is a series of integral components that function in unison to prevent moisture intrusion into the facility. The system configuration is generally similar in all waterproofing applications. The material components that are common to all types of waterproofing applications are the structural substrate, flashing, membrane and insulation.
Plaza deck (horizontal) waterproofing: Horizontal applications — below grade or on grade — typically consist of the following component configuration:
- Structural deck
- Protection board
- Drainage (surface drains)
- Wear surface
Below-grade (vertical) waterproofing: The typical system configuration for below-grade vertical applications is as follows:
- Structural substrate
- Drainage course
Mud mats: Below-grade waterproofing typically begins on grade at the mud mat. A mud mat is an unreinforced concrete slab or gravel bed that is applied under the foundation. The intent of the mud mat is to prevent groundwater from entering the slab surface. Buildings constructed at sites with high water tables should always include a mud mat.
These slabs are used as reasonably stable, all-weather assembly platforms to receive the waterproofing for the underside of the wear slab, as well as to support, with little or no deflection, the rebar chairs and rebars during installation of the reinforced wear slab. Such non-reinforced ground slabs do take on moisture and water, which will cause the disbanding of any waterproofing system from these ground slabs whether it is a liquid or reinforced membrane. This is a point that should be constantly considered when selecting protective materials and systems.
Membrane installation at the mud mat is based on the substrate. Over concrete slabs the membrane should be fully adhered. At gravel beds adhesion is not possible, so the bottom membrane may be loose laid with adhered joints. If an additional membrane is required it should be adhered over the bottom membrane. The mud mat waterproofing should project 9 to 12 inches beyond the foundation so that the vertical membrane can be turned out over the exposed toe of the horizontal surface.
Substrate: Waterproofing can be applied over various substrates such as concrete, cement fiberboards, gypsum boards or wood. Concrete provides the best substrate material for waterproofing systems. The preferable concrete substrate is a cast-in-place monolithic structural concrete slab. This is more suitable than pre-cast concrete because pre-cast concrete requires a nominal 2-inch-thick topping to provide a smooth, continuous top surface to eliminate the control joints. Control joints are susceptible to openings from the bearing ends of the pre-cast structural members and would require expansion joints to accommodate movement between the slabs.
Flashing: Waterproofing flashing is applied prior to membrane application. This is in contrast to roof systems, in which the membrane is applied prior to the flashing. Flashing is applied at internal and external corners, penetrations, cold joints, expansion joints, changes in elevations and all vertical surfaces. The flashing material must be approved by the membrane manufacturer and applied in accordance with the manufacturer’s requirements.
An important characteristic of flashings is the reinforcement material. Lack of proper flashing reinforcement has contributed to many premature failures. Cold joints at the wall/footer and wall/structural floor slab junctures are particularly critical. Use of compatible fabrics or felts for flashing reinforcements should always be required at the vertical and horizontal interior and exterior corners for both cast-in-place concrete and concrete masonry units, whether at plaster-type wall bracings or at the corner changes in the direction of the walls themselves.
Membrane: Waterproofing should be applied over all exposed substrate surfaces, particularly concrete. Membrane under pressure slabs on the ground can extend under the foundation walls and over the pile caps. Foundation waterproofing must extend above grade a minimum of 8 inches. The waterproofing materials must be covered with a metal flashing, masonry or stucco, and it should be terminated above grade. This is required because most waterproofing materials are not ultraviolet resistant and must be covered.
The type of material used in the system determines the application methods. Waterproofing membranes include:
- Built-up bituminous membranes
- Modified bitumen sheets
- Liquid-applied membranes
- Prefabricated elastomeric sheets
- Prefabricated thermoplastic sheets
To be effective, waterproofing should consist of a total or continuous envelope of the below-grade structure, which provides a complete enclosure of all areas that are subjected to hydrostatic pressure and/or chemical pollutants. Interruptions at walls that are not protected with through-wall flashings or other continuations of the waterproofing system will nullify a waterproofing barrier, rendering it ineffective.
Insulation: Insulation applied in waterproofing systems serves two fundamental purposes: thermal resistance and membrane protection. Insulation in waterproofing systems should always be applied above the membrane. In both vertical and horizontal applications, insulation protects the membrane from backfill and construction traffic when it is applied over the membrane. Waterproofing systems are exposed to higher traffic loads than roof systems, and the insulation serves as further protection with its high compressive strength. Insulation’s thermal resistance is much greater than aggregate or earth fill on heated and air-conditioned occupied spaces. Even in the coldest climates, the insulation — when applied above the membrane — will maintain the membrane temperature above the dew point, eliminating condensation.
Because of the placement of the insulation in a waterproofing system, there is only one insulation choice: extruded polystyrene board. Extruded polystyrene is the only commercially available insulation that provides both a high compressive strength (60 psi) and moisture resistance. Moisture resistance is required because the insulation is not protected and it is exposed to continual moisture infiltration. Studies have indicated that extruded polystyrene retains approximately 80 percent of its dry thermal resistance in continually wet conditions. Insulation should be set in a fully adhered application on vertical surfaces. Insulation application on horizontal surfaces should be in accordance with the waterproofing system manufacturer’s requirements.
Protection board: Protection boards are required to shield the membrane from damage inflicted by other trades and ultraviolet radiation. Since the waterproofing membrane is the first component completed, it is not unlikely that traffic from members of other trades could damage the completed membrane, as could their equipment, machinery, scaffolding or dropped tools. The protection board should be applied prior to exposure of other trades immediately after the flood testing of the waterproofing membrane is completed. Any repairs required after the flood testing is completed should be performed prior to the application of the protection board.
The most common type of protection board is an asphalt-core, laminated panel that comes in thicknesses of 1/16, 1/8 or 1/4 inch. This panel is faced with polyethylene film on one side that is applied to prevent the panel from sticking during transport and storage. Some manufacturers also promote the use of a minimum 6-mil-thick polyethylene film as a protection layer. The reasoning is that membrane deficiencies are easier to detect and repair with the nominal protection layer. A general word of caution is that the minimal protection layer is more susceptible to damage from equipment, machinery and scaffolding.
Drainage in vertical applications: Below-grade waterproofing is subjected to water transmission from two sources — surface water and groundwater. Proper control and drainage of these water sources is required for successful waterproofing system performance. Sources of surface water include rain, melting snow and sprinklers. The most effective form of controlling surface water is by directing it away from the structure. This can be achieved through sloping of the landscape, and by installing roof gutters and downspouts that divert water away from the structure. Moisture infiltration in above-grade components (masonry, siding, etc.) could work its way down and create leaks in below-grade areas.
The control of groundwater is more complicated because groundwater levels fluctuate throughout the year. The waterproofing membrane must be designed and applied to accommodate groundwater when it is at the highest level, even if this is a temporary or infrequent condition.
Proper below-grade waterproofing design must include a system for collecting, draining and discharging groundwater away from the structure. The most effective way to properly collect and discharge groundwater is through the use of foundation drains. Foundation drains can be field-constructed drainage systems or prefabricated soil drainage systems.
Drainage in horizontal applications: Drainage components for a plaza deck with a wearing surface typically include (from the substrate up):
- Membrane with protection board
- Filter fabric
- Pea gravel or geotextile mat
- Wear surface
Drainage components for a plaza deck with earth-covered topping typically include (from the substrate up):
- Membrane with protection board
- Filter fabric
- Pea gravel or geotextile mat
- Polyethylene sheet
- Pea gravel
- Filter sheet
Drainage systems on horizontal applications should be comprised of all components from the wearing surface down to the membrane. Horizontal drainage is required at two levels: the wear surface and the membrane level. At the wear surface, drainage is required to minimize saturation that may occur from disintegration during freeze-thaw cycling. At the membrane level, drainage is required to accommodate hydrostatic pressure from accumulated drain water, freeze-thaw cycling of trapped water and the reduction of the insulation’s thermal resistance.
Proper drainage can be achieved by adequately sloping the horizontal substrate a minimum of 1 to 2 percent to allow proper flow to the drains. The drainage course medium is either gravel or plastic drainage panels.
Types of Waterproofing Systems
Waterproofing systems are required on all below-grade surfaces that are (1) occupied and (2) subjected to hydrostatic pressure. It is the architect or designer’s responsibility to specify the system that is best suited for the facility. There are five basic types of common positive-side waterproofing systems used in commercial construction. The type of material used in the system determines the application methods.
Reinforced sheet membranes: Because of their proven reliability over the years, reinforced sheet membranes are the most common type of system used in vertical applications. There are manufacturers in the United States that have supplied these systems for more than 60 years.
Materials for reinforced sheet membranes are manufactured with a specially engineered polymer applied over a reinforcement to produce a membrane sheet. The sheet is applied in the manufacturer’s mastic and/or adhesive. The reinforcement of the materials used for the waterproofing barrier normally provides a uniform thickness in application. Most manufacturers will stipulate that their protective coatings are applied to the point where the weave of the fabric does not show. This provides a smooth, liquid-only appearance and a monolithic application with no seams.
The main advantage of these systems is that the built-in reinforcement through the use of felts and/or fabric has supplied additional forgiveness of structural movement obtained through settlement, curing of the concrete and the normal accommodations of the building to temperature differentials. This accommodation or forgiveness by the membrane helps to ensure a continuous barrier against the infiltration of water in both liquid and vapor forms.
Hot-applied bitumen systems: Hot bituminous systems have been used since the beginning of waterproofing. These systems employ multiple plies of fabric, felt, or felts and fabrics combined. They are applied in alternating layers of bitumen (coal tar or asphalt) and felt (fiberglass or organic). The bitumen serves as the waterproofing agent and adhesive. The felts and/or fabrics provide reinforcement, which stabilizes the membrane and provides tensile strength.
These systems have routinely provided life spans of 30 years or more and were common in past decades. The other system advantage is redundancy – three to five plies of reinforcement provides exceptional durability.
The application of hot-applied systems has declined in the past two decades because of safety risks and concerns with the odors from the fumes. Caution is required when these systems are applied on vertical surfaces because the materials are heated to 400 degrees Fahrenheit or more. When installed near existing building intakes these systems can pose fume problems.
Although certain application techniques are similar to roofing, the asphalt bitumen used in waterproofing is a different type of material. The asphalt used in roofing is blown to produce a soft, viscous state. Asphalt used in waterproofing is not blown, thereby creating a harder substance for the required water repellence. Blown asphalts are also susceptible to deterioration with soil contaminants, which is another important criterion of waterproofing systems.
Liquid-applied systems: Liquid-applied membranes (LAMs) are field applied using a variety of liquid components that are installed directly to the substrate. These liquid systems usually require a primer and then a multiple-coat application of the liquid materials to overcome any surface tension presented by the substrate surface, which could cause pinholing. The number of coats necessary can vary from manufacturer to manufacturer depending on the material type and its viscosity. Some manufacturers require two layers of liquid material with a sheet of fibrous matting in between. This creates a stronger waterproofing barrier.
LAMs can be applied with hot or cold polymer modified asphalts. Hot-applied systems are heated to 400 degrees Fahrenheit in specialized equipment and applied in thicknesses up to 180 mils. The most important design criteria for improved material performance are the materials solids content and coating thickness. The material’s solids content should be a minimum of 80 percent. The minimum specified coating thickness should be 60 mils. This is required to reduce stress concentration from irregular substrate conditions, such as cracks, honeycombs, etc.
These systems allow for both above- and below-grade application, including planters and split-slab construction. They are not resistant to ultraviolet weathering and cannot withstand foot traffic, so they should not be applied on exposed areas. When LAMs are applied on horizontal applications, a sub slab must be in place for application of the membrane. A topping of concrete, tile or other hard finishes is required. LAMs are applicable over concrete, masonry, metal and wood surfaces.
Single-ply membranes: Single-ply membranes are coated with a variety of films consisting of modified bitumen, ethylene propylene diene monomer (EPDM), butyl rubber, styrene butadiene styrene (SBS), and atactic polypropylene modifications of asphalt and catalytically blown asphalt.
The systems are fully adhered to the substrate surfaces and — in most cases — the seams are heat welded. The critical components determining single-ply use for waterproofing over roofing applications are the materials water absorption capacity and resilience to ground chemicals. The maximum water absorption rate for waterproofing materials is 3.2 percent by weight. Some modified bitumen sheets have absorption rates of nearly 10 percent. Polyvinyl chloride (PVC) and butyl rubber typically have the lowest absorption rates of nearly 2 percent. Butyl rubber and PVC also offer significant chemical resistance. The PVC used in waterproofing sheets includes additives to resist chemicals (such as alkaline and algae) in lieu of the ultraviolet stabilizers and high temperature inhibitors that are added to PVC roofing sheets.
Thermoplastic sheets are available in three compositions: PVC, chlorinated polyurethane (CPE) and chlorosulfonated polyethylene (CSPE or Hypalon). The membranes are available in varying thicknesses. PVC membranes are 30 to 60 mils thick, CPE membranes are 30 to 60 mils thick and CSPE are 30 to 35 mils thick.
Bentonite clay: Bentonite is a traditional waterproofing material that dates back nearly 80 years. Bentonite is a granulated smectite clay that provides waterproofing by swelling to nearly 15 times its dry volume when it absorbs water. The swelling is caused by the material’s molecular structural form of expansive sheets that can expand based on the grading and clay compositions. More recently, the advanced technology of polymer chemistry has increased the use of bentonite by making it a more versatile material. It is currently offered in four forms:
- Prefabricated panels
- Prefabricated geotextile sheets
- High-density polyethylene sheets
- Trowelable mixtures used for detailing
These changes in technology have added to ease of application. Older benonite applications were conducted by skilled workmen through spraying and troweling applications that required uniform thickness. The current benonite panels are applied by laying the panel on the substrate, properly lapping the panels and nailing them to the substrate.
Bentonite sheets typically contain 85 to 90 percent of montmorillonite clay and a maximum of 15 percent natural sediments such as volcanic ash.
The application of bentonite is typically successful for blindside waterproofing in deep excavations and structures without sensitive occupancies that require the minimal risk of leaks or humidity control. The main advantage of bentonite is that it can be placed over concrete surfaces almost immediately after the forms are removed. One potential concern is that the material must be covered directly after application. Any contact of the cardboard exterior with precipitation (rain, snow, dew, etc.) will contribute to material deterioration and odors.
Considerations for Selecting a Waterproofing System
There are several considerations that an architect or waterproofing designer must examine prior to the selection of a waterproofing system. Some of the considerations include:
- Water table
- Soil characteristics
- Substrate stability
- Construction sequence
- Track record
- Risk vs. cost
- Ease of application
Occupancy: Important design factors to consider include the leak risk tolerance and sensitivity to humidity of an occupied space. Leaks are intolerable in occupancies with book storage, art storage, computer rooms, electrical switchgear and medical facilities. These types of facilities also require tight humidity control. Intrusion of air can be as detrimental as intrusion of water in sensitive facilities. Medical facilities, research and testing laboratories fit within these classifications. Proper membrane design for the aforementioned facilities would require positive side waterproofing with a low vapor permeable membrane.
Water table: The water table level is an important consideration that not only determines the type of waterproofing required, but, by code, whether waterproofing is required at all. The International Building Code requires that waterproofing or dampproofing is applied on all below-grade structures where the groundwater table is maintained a minimum of 6 inches below the ground slab.
Accurate soil bearings — completed by a competent civil engineer — are required prior to waterproofing design. In the Northern Hemisphere, the water table is usually highest after the spring thaws have saturated the ground. The water table is lowest following the summer evaporation of the surface moisture. Proper waterproofing design should be based on the maximum water table level for the site.
Soil characteristics: Waterproofing materials are unique because they are typically exposed to much harsher conditions than any of building’s other exterior components. Most of the exposure elements are continuously present at the waterproofing surface and do not dissipate, as they do at the other exterior components. For example, water can be present in below-grade surfaces for weeks, whereas roof systems are designed to eliminate ponding water within 48 hours.
Chemicals in the soil can have an adverse effect on some materials, and knowledge of potential chemicals present is required for proper design. Chemical properties in soils can adversely affect waterproofing in various ways. Acids and alkaline in groundwater can accelerate the deterioration of concrete and steel reinforcing bars. Salt in water corrodes reinforcing bars in concrete. Sulfates can have a negative reaction with Portland cement, resulting in internal shearing stress that causes spalling. Other chemicals that affect waterproofing are calcium hydroxides, oils and chemicals from fertilizers.
The physical properties of the soil can also affect waterproofing. Clay soils of low permeability limit underground hydrostatic pressure. The intensity and nature of hydrostatic pressure can force water into tie-rod holes, cold joints and rock pockets. Hydrostatic pressure can also turn minor imperfections into probable sources of leaks.
Substrate stability: Waterproofing is applied on substrate surfaces to protect the substrate from structural deterioration caused by water, chemicals and soil. The applied waterproofing material must also be capable of performance if the substrate becomes unstable or minor imperfections occur. Some substrates are inherently prone to imperfections, and this tendency should be considered prior to waterproofing design.
Waterproofing membranes applied over substrates that are vulnerable to cracking from any source must be elastic and capable of resealing. Cracks can occur in masonry or other waterproofed components that have multiple construction joints. Dampproofing should not be considered in these conditions.
The types of soils at the site can also have an impact on substrate stability. Expansive soils and peaty soils can produce rising and settling footings that can cause cracks in footings and foundation walls. All substrate openings can become potential points of moisture infiltration.
Construction sequence: Waterproofing is applied in phases as construction of walls and plaza decks are installed. There may be extended periods of time between certain waterproofing applications and final completion. For instance, waterproofing of below-grade walls is typically done in 6- to 8-foot increments from the bottom to the top. The initial section is finished, the site is backfilled and the waterproofing applicator uses the backfill as a scaffolding to complete the next increment. This process is continued until the full wall is waterproofed. This process could continue over an extended time period because the waterproofing applicator relies on the pour schedule and backfilling operations.
Installed waterproofing materials are rarely exposed to exterior elements after final application procedures are completed. The membranes are covered by soil, concrete or another type of top surfacing. However, because of the initial construction sequence, these materials may be exposed for an extended period of time. This fact must be considered in the material selection process.
It is important to prevent the exposure of vulnerable materials to the elements when long delays in the schedule occur. Waterproofing materials must be capable of withstanding freezing temperatures if they are to be exposed to these conditions for more than one week. Exposure to rain and water can also be a concern. If bentonite clay is used, it must be adequately covered.
Membranes with a low resistance to ultraviolet radiation can deteriorate if the materials are exposed to sunlight for intervals as short as one month. If the waterproofing is applied prior to the completion of the structural elements, it may prompt negative effects on the waterproofing such as deflections or other imperfections.
Track record: In the last decade, the waterproofing market has become very competitive, and manufacturers that provide other exterior building component materials — primarily roofing — have entered the market. Some of these products might be well suited for a given application; others may not. One simple way to evaluate a product is to check its track record in similar waterproofing applications. Sources of information could include other designers, building owners, contractors or specialty consultants.
It could also be beneficial to ask specific questions of the manufacturers. The first question should be: Is the product manufactured by the seller, or is the seller merely a distributor (through a private label agreement)? This is very common in the construction materials industry. Manufacturers typically private label some or all of the system components. This type of information is available through Dun & Bradstreet.
What is the manufacturer’s track record? Contact other designers or waterproofing contractors in your area or throughout the country to find out their history with these materials. Material performance — good or bad — is usually a topic of conversation. If you talk to other industry professionals or manufacturers, it would also be important to find out if the product has a history of successful performance under comparable conditions for at least 15 to 20 years. Designers should be skeptical of other building component materials being marketed for waterproofing applications without a track record in similar conditions. No other building component is exposed to the conditions waterproofing materials must withstand.
Another important consideration is whether the material has maintained a consistent formulation over the past 10 years. This is a significant concern at this time. Environmental regulations and depletion of natural resources have had a great impact on current material formulations. Products that we have relied on for hundreds of years are not as readily available. This has left the industry with materials and formulations with no verifiable track record.
Risk vs. cost: The designer should always minimize risk despite any reasonable — or unreasonable — costs. If a building owner or general contractor wants to cut costs, the waterproofing system is not the place to do so. As noted, the cost incurred for even minor repairs could easily exceed the initial cost of the system.
Ease of application: Compared to the other concerns, ease of application is a minor factor, but since it may result in better workmanship, it should be considered. There will also be projects where access or space constraints are an issue. Application methods, particularly material adhesion methods, may be determined by the site constraints. On projects where other factors are in balance, ease of application of a material or a system can be a determining factor in material selection.
Guidelines for Proper Waterproofing Specifications
Thorough specifications are a critical component and are paramount to the success of a waterproofing project. The proper development of specifications is essential due to the complexity of the waterproofing process, which requires the smooth integration of several building components and trades. It is the responsibility of the architect and/or designer to ensure that all divisions of waterproofing application are addressed. The specification of materials and system application methods are important elements, and they should be chronicled along with excavation, substrate preparation, backfilling and sequencing of work.
A thorough specification will serve as an effective communication tool for all project participants. A good specification, which encompasses the scope of work, will also serve as a valuable tool to enable the owner or owner’s representative, construction manager, applicator and inspector to effectively communicate with each other. It also serves as a communication path to the architect. The specifics of each component and divisions of responsibility should be provided in the specifications, which should be reviewed before and during the development process in order to attain a high-quality waterproofing system that meets the specific project requirements.
On below-grade applications the specification should be divided into four sections that address excavation, surface preparation, waterproofing application and backfilling. MASTERSPEC or CSI format specifications address these procedures in the following divisions:
- Division 1 – Pre-Installation Meeting (Excavation)
- Division 2 – Backfill
- Division 3 – General Requirements (Surface Preparation)
- Division 7 – Waterproofing
Division 1 – Pre-Installation Meeting (Excavation): The intent of this section is to establish parameters of the pre-installation meetings. Typical projects may have as many as three such meetings, which serve to open the lines of communication between the project participants. Attendees should include representatives from the owner, architect, engineer, general contractor, subcontractors, material manufacturers and the inspection agency. The specifications should define when the meetings will take place and who should attend. They should also define the guidelines for excavation, sequencing and review of the completed concrete surfaces.
The purpose of these meetings is to resolve any questions or disputed areas in the specifications prior to project commencement and during the construction phase. In relationship to these issues, the specifications should clearly define the following issues:
- The required width of the foundation excavation.
- Sequencing of concrete casting for (a) the footing, (b) the slab on ground and (c) the structural slab.
- Sequencing of the backfill operation.
- The waterproofing contractor’s review process for concrete finish. It is critical that the specifications make it clear who is responsible for concrete repair.
- The waterproofing contractor’s review of the surface moisture requirements.
Division 2 – Backfill: Whereas Division 1 outlines the sequencing requirements of the backfill operations, Division 2 defines the technical requirements of this process. The backfilling process is a critical component to the success of a waterproofing system, and it requires the appropriate attention in the specifications. Damage created by improper backfilling is the most common cause of premature waterproofing failures. Damage typically results from the use of improper fill materials, such as rocks, frozen soil and miscellaneous debris. It also occurs from punctures created by backfill equipment, such as loaders, bulldozers, shovels, etc. Backfilling operations have also been erroneously completed prior to the waterproofing application, leaving the entire area exposed to moisture infiltration. This is often the result of an overanxious or uncaring subcontractor.
Proper backfill requirements listed in the specifications can eliminate these errors by providing an enforceable document. If it is determined that incorrect application materials and methods were used, then corrective remedies would be required. The most important backfill requirement is that it is completed immediately after waterproofing is applied. This is critical for two reasons. In vertical applications, the backfill holds the membrane in place. It also provides ultraviolet protection for the waterproofing materials, particularly for those materials that are not resistant to ultraviolet rays.
Some of the other backfill requirements that should be provided in the specifications include the following:
- Require that the compaction of the backfill is in accordance with ASTM D 1557, “Test Method for Laboratory Compaction Characteristics of Soil Using Modified Effort.”
- Specify single-graded aggregate that is not less than 3/4 inch in size.
- Specify filter fabric, porous backfill and subsurface drains.
- Limit backfill lifts to a maximum of 12-inch heights.
- Specify field inspection of the backfill operation to ensure compliance and that no damage to the waterproofing occurs.
Division 3 – General Requirements: A successful waterproofing application is dependent on proper substrate preparation. Preparation requirements vary by the type of material used and application methods. It is important that the manufacturer’s requirements for substrate preparation are followed. In this regard, specify that the concrete surfaces and finishes meet the manufacturer’s requirements.
The designer should specify proper substrate preparation in the concrete division of the specifications. Typically, separate trades are responsible for concrete placement and waterproofing application, and this can create confusion and problems, particularly in regard to what is considered proper concrete preparation and whose responsibility it is to perform the repairs required for the successful waterproofing application.
The designer can eliminate these issues by providing language stating that concrete placement and repair be performed in accordance with ASTM D 5925. This is an excellent reference guide that contains a list of remediation measures for identifying and repairing fins, bug holes, form kick-outs and similar surfaces that are unsuitable for the application of waterproofing. Reference to this standard in the Concrete Section and Waterproofing Section will eliminate potential problems during the project. The designer should also require that the waterproofing contractor approve the surface in writing prior to installation.
Other preparation items to be listed in the specifications include:
- Do not permit the use of concrete curing compounds, certain form release agents or concrete admixtures that are not approved by the waterproofing manufacturer.
- Specify schedule of concrete pours to provide for proper curing time prior to waterproofing application.
- Specify concrete surface quality and finishes (float, steel trowel) that meet the manufacturer’s requirements.
- Require the concrete contractor to exercise care when pouring concrete over waterproofed systems. Provide that there shall be notification of any damage to the waterproofing system given to the waterproofing applicator prior to the concrete pour or covering.
- Specify water stops.
- Specify cement cants and chamfered corners if required.
- Any solvent-bearing concrete sealer should only be specified and applied after approval in writing by the waterproofing system manufacturer. A solvent-bearing sealer applied in normally specified quantities could migrate through the joints of the wear surface, changing the viscosity of the waterproofing system.
Division 7 – Waterproofing: Part 1 of the waterproofing section should include standard language pertaining to general requirements. These requirements would include submittals, manufacturer requirements, application methods and weather conditions required for application, and scheduling of waterproofing and backfilling. This section should also specify the application and materials required for temporary protection of the waterproofing while other trades are working in the area.
Part 2 of this section should list the products required for the waterproofing systems. A brief description should be provided for all products listing information applicable to the application — i.e., size, type, thickness, psi, etc. Reference the ASTM number for all products:
- Type I Asphalt, ASTM D 449
- Type I Coal Tar, ASTM D 450
- Type IV Glass Felt, ASTM D 2178
- Woven Glass Fabric, ASTM D 1668
- Coal Tar Saturated Organic Felts, ASTM D 227
- Liquid Applied Membranes, ASTM C 836
- Extruded Polystyrene, ASTM C 578
In reference to extruded polystyrene, it is recommended that Type VII EPS with a minimum of 60-psi compressive strength is used on framed slabs under a wearing surface and Type I EPS as a protection layer on vertical surfaces.
Specify the following accessory materials:
- Protection board
- Drainage panels
- Termination bars
- Filter cloths under concrete slabs
Part 3 of this section should reference the surface conditions required for waterproofing applications. Surface preparation and acceptable moisture conditions should be in accordance with the manufacturer’s requirements. Test methods to determine existing surface moisture should be specified.
The application section should include the following items:
- Specify the installation of the flashing and reinforcing prior to the membrane.
- Specify the type of flashings, reinforcing materials and possible flashing termination fixtures to be used when detailing flashings at all openings, projections, and other terminations appropriate to the methods and systems specified.
- Specify appropriate means for anticipated substrate movement. This can be accomplished through appropriately designed and placed control and expansion joints.
- Follow the manufacturer’s guide specifications and details for applicable materials and application methods.
- Specify that the manufacturer provide approvals as to the intended use of the system and details. This can be in the form of a written statement of “suitability of use.”
- Establish the manufacturer’s limitations and requirements during application for weather conditions such as temperature, rain, snow and wind.
- Specify immediate installation of protection board so there is no damage to the system from other trades. Use the manufacturer’s requirements as to the type and placement. For horizontal protection, generally accepted protective cover is obtained by means of asphalt/organic felt protection boards 1/8 to 1/4 inch thick — depending on required protection. For vertical protection, generally accepted protective cover consists of polystyrene bead board with a minimum of 1 pound density and 1 inch thick.
- Specify subsurface and below-grade pre-fabricated drainage systems in accordance with the manufacturer’s approval and requirements. Some manufacturers neither require nor approve these systems. A properly sloped concrete surface — 1/4 inch per foot or more — will typically remove 95 percent of all water to the drains.
- Drain configurations and installation elevations should be properly detailed and approved by the waterproofing manufacturer.
- Require a flood test on all horizontal applications for a minimum of 24 hours and a maximum of 72 hours using no more than 2 inches of water. Tests are typically performed prior to application of the protection board for easy access to system repairs.