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| The
condition of the substrate is important for proper material adhesion. Most
waterproofing manufacturers have specific requirements regarding the condition
of the substrate that they are covering. (Photo courtesy of American Hydrotech,
Inc.) |
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Surface
Preparation
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.
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| Proper
design for the application phase should include the manufacturer’s application
rate requirements. A copy of the manufacturer’s application requirements should
be included as part of the project submittals for easy reference during the
application. (Photo courtesy of American Hydrotech, Inc.) |
|
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.
