Power Washing
A power washer should have a pressure ranging from 2000 - 2200 psi (lbs. per square inch) and a fan style or rotary nozzle.
Power washing will solve several problems at the same time
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Remove loose materials and mildew that may or may not be visible.
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Flush-out dirt or vegetation growing in the cracks, allowing a good bond for the crack fillers.
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Thoroughly clean the surface and surface pores allowing an excellent bond for the new coating materials.