Page 131 - Construction Waterproofing Handbook

3.20 CHAPTER THREE
condensation. Note that some silicone-based systems, such as silanes, must have moisture pre-
sent, usually in the form of humidity, to complete the chemical reaction.
Substrate cracks are repaired before sealer application. Small cracks are filled with non-
shrink grout or a sand–cement mixture. Large cracks or structural cracking should be
epoxy-injected. If a crack is expected to continue to move, it should be sawn out to a min-
1
imum width of 4 in and sealed with a compatible sealant.
Note that joint sealers should be installed first, as repellents contaminate joints, causing
sealant-bonding failure. Concrete surfaces, including large crack patching, should be cured
a minimum of 28 days before sealer application.
All adjacent substrates not being treated, including window frames, glass, and shrub-
beries, should be protected from overspray. Natural stone surfaces, such as limestone, are
susceptible to staining by many clear sealers. Special formulations are available from man-
ufacturers for these substrates. If any questions exist regarding an acceptable substrate for
application, a test area should first be completed.
All sealers should be used directly from purchased containers. Sealers should never be
thinned, diluted, or altered. Most sealers are recommended for application by low-pressure
2
spray (20 lb/in ), using a Hudson or garden-type sprayer. Brushes or rollers are also accept-
able, but they reduce coverage rates. High-pressure spraying should be used only if
approved by the manufacturer.
Applicators should be required to wear protective clothing and proper respirators, usually
the cartridge type. Important cautionary measures should be followed in any occupied struc-
ture. Due to the solvents used in most clear sealers, application areas must be well ventilated.
All intake ventilation areas must be protected or shut off, to prevent the contamination of inte-
rior areas from sealer fumes. Otherwise, evacuation by building occupants is necessary.
Most manufacturers require a flood coating of material, with coverage rates dependent
upon the substrate porosity. Materials should be applied from the bottom of a building,
working upward (Fig. 3.6). Sealers are applied to produce a rundown or saturation of about
6 in of material below the application point for sufficient application. If a second coat is
required, it should be applied in the same manner. Coverage rates for second coats
increase, as fewer materials will be required to saturate a substrate surface.
Testing should be completed to ensure that saturation of surfaces will not cause dark-
ening or add sheen to substrate finishes. Dense concrete finishes may absorb insufficient
repellent if they contain admixtures such as integral waterproofing or form-release agents.
In these situations, acid etching or pressure cleaning is necessary to allow sufficient sealer
absorption. Approximate coverage rates of sealers over various substrates are summarized
in Table 3.11.
Priming is not required with any type of clear sealer. However, some manufacturers rec-
ommend that two saturation coats be applied instead of one coat. Some systems may
require a mist coat to break surface tension before application of the saturation coat.

CEMENTITIOUS COATINGS

Cementitious-based coatings are among the oldest products used for above-grade water-
proofing applications. Their successful use continues today, even with the numerous clear