Waterproofing Design Guidelines: Execution
February 4, 2010
Typical design specifications that are prepared in the CSI Master Format include three sections for Division 7: Part 1 - General, Part 2 - Products, and Part 3 - Execution. Parts 1 and 2 are important for defining preparatory work, division of responsibilities, communication and selection of required materials. The Execution portion - Part 3 - defines the installation procedures required for a successful waterproofing application. The execution section should include requirements for surface preparation and material application. This article provides some guidelines for specification preparation and includes recommendations for application requirements of various waterproofing systems.
In recent years the materials and systems that we have been using for waterproofing have experienced changes due to environmental issues, labor constraints and the depletion of natural resources. One of the biggest effects of these changes has been that proper application requires thorough surface preparation. Surface conditions are particularly important for adhered materials.
The condition of the substrate is important for material adhesion. Most waterproofing manufacturers have specific requirements regarding the condition of the substrate that they are covering. This is particularly true with concrete, which is the most prevalent substrate in commercial waterproofing applications. The waterproofing manufacturer may require specific trowel finishes for adhesion of their materials and they may want to have input as to the type of concrete curing materials used -if any - because this may prohibit full material adhesion.
Defects and deformations in the concrete must also be addressed in both both vertical and horizontal applications. The designer should always reference ASTM D 5295, “Preparation of Concrete Surfaces for Adhered (Bonded) Membrane Waterproofing Systems,” for guidelines on the proper preparation of concrete surfaces. This standard provides proper finishes for concrete surfaces, lists a number of typical concrete defects and provides proper repair methods. The inclusion of the referenced standard in the design documents will eliminate misinterpretation of responsibility and performance requirements during the project.
It is recommended that the designer indicate that the manufacturer provide a written document including their concrete finish requirements, curing time required for application and prohibited curing compounds. The designer should also require a written statement indicating that preparatory inspections have been completed and that they are in acceptance of the substrate prior to application. These conditions are typically provided in Division 3 of the design documents.
Some waterproofing materials require application to dry surfaces. In these cases, it is important that the designer stipulates that proper testing is conducted prior to application. In most cases the moisture testing should be determined by the manufacturer with the testing performed by the applicator. There are four acceptable methods of moisture determination listed in ASTM E 1907, “Standard Practices for Determining Moisture-Related Acceptability of Concrete Floors to Receive Moisture-Sensitive Finishes.” They are:
1. Conductance moisture meters.
2. Gravimetric tests.
3. Vapor transmission through slab.
4. Presence of condensation under a plastic sheet that is taped to the substrate for 24 hours.
The standard requires that moisture testing is completed in every 1,000-square-foot section of slab. Two or more tests may be conducted to certify test results. Another way to certify material adhesion is to simply adhere the material to the substrate and try to pull it off.
Most waterproofing manufacturers require that flashing be installed prior to the membrane application. This differs from roof assemblies, where the flashing is always applied over the membrane. All waterproofing flashings - at vertical transitions, penetrations and terminations - should be reinforced. Reinforced flashings are even required on liquid-applied systems - hot or cold - that have no reinforcement.
Surface preparation for adhered systems includes removal of all dirt, dust and contaminants. The cleaning process includes removal of any concrete curing compounds that may adversely affect the waterproofing materials adhesion capacity. Substrate cleaning can be completed with brooms, vacuums or air sprayers. All concrete surface irregularities should be repaired in accordance with ASTM D 5295. On liquid-applied membranes, concrete cracks equal to or greater than the width of the system should be covered over with an application of the system fabric prior to system application.
The preparation section of the design documents is also the point where any required surface treatments are detailed. Most bituminous and modified bitumen waterproofing membranes require that the surface is primed prior to application. The design documents should provide the type of primer that is required, application rates and ambient temperatures and weather conditions suitable for application.
For bentonite systems, removal of all mud, contaminants and ground water residue is required. Water-jet removal may be required to thoroughly remove any contaminants that may interfere with the adhesion of the bentonite to the substrate.
The Application Phase
It is the responsibility of the designer to make certain that the design documents are as thorough as possible. This is particularly important at the application phase. Design documents that are not thorough leave room for interpretation by the applicator. In many cases, the applicator might have a different interpretation, which could lead to project conflicts and even litigation.
The waterproofing barrier - liquid or membrane - should be applied directly to the substrate. Membranes should be fully adhered to the substrate. Partial attachment or loose-laid materials may be subject to moisture intrusion at the substrate level if the waterproofing is not fully adhered. Proper design for the application phase should include the manufacturer’s application rate requirements. For non-proprietary specifications, include a statement referencing application rates should be in accordance with the manufacturers latest printed requirements. A copy of the manufacturer’s application requirements should be included as part of the project submittals for easy reference during the application. A best waterproofing design practice is to require the installation of protection board (or layer) immediately after waterproofing application. This protects the waterproofing from ultraviolet damage and construction traffic.
The designer must also make reference to the ambient weather conditions required for material application. The current waterproofing materials are more sensitive to weather conditions - particularly heat and cold - due to the fact that more adhesives are being used. Temperatures have an impact on material curing times and some materials may not be applied if precipitation is forecasted within a 24-hour period of application.
The materials application requirements over cured concrete are also important. Some waterproofing materials can be applied over green concrete, whereas other materials require a minimum 27-day cure time. Again, the manufacturer’s requirements relating to this matter must be included in writing as part of the project documents if they cannot be included in the original design.
Each material and system has its own specific application requirements. The designer should be aware of specific requirements and provide the proper application requirements for the specific material and/or system. For hot-applied systems, the designer should state that the heating equipment should have a thermometer on the equipment so that verification of application temperatures can be conducted. The application temperature should be within 25 degrees F (plus or minus) of the manufacturer’s required application temperature. Hot-applied membrane systems require uniform moppings that must be within 15 percent (plus or minus) of the manufacturer’s interply mopping rate. Require that all membrane defects - i.e., fishmouths, blisters, ridges, splits, etc. - are repaired immediately. Some manufacturers require an application of a glaze coat of bitumen over the completed membrane surface. If required, it must be included in the design with proper application rates and heat temperatures.
Liquid-applied materials have become more common in horizontal applications. These products are more temperature sensitive due to curing. The designer should include the manufacturer’s application temperature requirements. It also recommended that the application rates are listed in percentages or mils (preferable method) as opposed to liquid content per unit area. If protection boards are required as part of the system installation, application should only commence after total system curing is completed. This usually requires one full day delay, but the manufacturer should always be consulted for specific timelines. Reinforced flashings should be used in all applications (even unreinforced liquid applications). Most manufacturers require unvulcanized neoprene or polyester for flashings at all vertical transitions, accessories and penetrations.
Self-adhered sheets require a waterproofing coating (typically adhesive or mastic) at all edges at the end of the day. These tie-ins are required to protect the completed waterproofing from moisture intrusion in areas not completed. Proper tie-in methods should be addressed in the design documents, especially in remedial applications over occupied spaces. It is also a best design practice to require additional rolling of seams to increase adhesion. Some manufacturers will even require application of liquid membrane at T joints. Protection board is required immediately after membrane application.
In single-ply applications - thermoset or thermoplastic - it is required that the material is laid out from the roll and set to relax prior to application. Typically this relaxation time span is 30 minutes or more. Seam application is the most critical component of these systems. Thermoplastic materials are commonly heat welded and this should be completed using the manufacturer’s required heating equipment. Seam application for thermoset materials is completed using the manufacturer’s required materials and application rates. Make certain that any bonding adhesives used in the thermoset application are not applied at field seams. It is also a best practice to apply cover strips at T joints for added protection.