Page 350 - Construction Waterproofing Handbook

8.10 CHAPTER EIGHT
used in conjunction with preparation of substrates for waterproofing applications. It is also
used in combination with other cleaning methods such as aggregate and chemical cleaning.
Pressure cleaners are manufactured to produce pressures varying from 300 to more
2
than 25,000 lb/in . The lower-pressure cleaners are used for rinsing minor residue accu-
mulation, whereas the higher-pressure machines remove not only pollutant collection but
also paints and other coatings. The wide range of pressures available require that testing
be completed to determine the pressures required to remove contaminants without dam-
aging substrates.
Equipment spray tips and operators directly control pressure-cleaning results. Fog-type
spray nozzles are desirable and impart little harm to a substrate, whereas O-tip nozzles
greatly concentrate the stream of water and can cause substrate damage.
Applicators must be experienced in this type of work, especially with higher-pressure
equipment. Unskilled mechanics can damage a building by blowing sealants out of joints,
damaging masonry or stone finishes, leaving streaks and performing insufficient cleaning
in the process. (See Fig. 8.8.)
Water soaking is a cleaning method preferred by preservations and historical restoration
professionals due to the minimal amount of damage possible. Water soaking is especially
successful on limestone structures, where chemical or pressure washing is unacceptable.
Specially prepared soaker hoses or sprayers are installed on upper building portions and
provide a continuous curtain of water flowing down the building facade. After an initial
period of soaking, determined by actual project testing, this method loosens dirt and pol-
lutant accumulations. These pollutants are then removed by low-pressure spray cleaning.
In highly contaminated areas, a repeat soaking process may be necessary to clean a build-
ing to acceptable aesthetic and project requirements.
A major disadvantage of water soaking is the amount of water introduced onto the
exterior envelope. If deterioration or leakage is occurring, this system will cause further

FIGURE 8.8 Pressure cleaning operation. (Courtesy of ProSoCo)