Cleaning Methods

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  • Cleaning methods should be tested prior to selecting the one for use on the building; The simplest and least aggressive methods should be selected.
  • The level of cleanliness desired should be determined; A new appearance look is both inappropriate and requires an overly harsh cleaning method.
  • Prolonged exposure of water causes rapid deterioration in older structures.
  • Take precautions to ensure that the water does not penetrate the surface and cause damage to the interior of the structure.
  • This procedure may cause corrosion of hidden iron work and steel anchors causing either staining or cracking due to the rapid expansion of the metal.
  • If the masonry remains saturated during the first frost, surface pieces may spall off as the water freezes.
  • Iron and chloride in the water can cause disfigurement and staining.

Surface Preparation:

  • Fill the buckets, usually one or two, with about two gallons of water.
  • Beginning at the top and gradually working down, scrub lightly with the fiber brush to remove any superficial deposits. Take care to avoid scratching or otherwise damaging any polished surfaces.
  • Rinse with clean, clear water.
  • Dry with clean, lint-free toweling or rags.
  • Tenacious mineral deposits may be treated locally with gentle abrasion using wooden paddles or sticks. Great care should be exercised to avoid damaging the highly polished where they exist.

NOTE: Low-pressure wash should measure between 100 psi and 400 psi. Medium-pressure wash should measure between 400 psi and 800 psi. High-pressure wash measures between 800 psi and 1200 psi.


  • Spray-apply water to masonry surfaces to comply with requirements specified by RHPO for location, purpose, water temperature, pressure, volume and equipment.
  • Heat water, if required, to effectively aid dirt removal and to clean surfaces.
  • Clean with spray nozzle tip held consistently a minimum of 12-inch distance from masonry surface and direction of stream perpendicular to the surface unless other working distances and angles of spray direction are approved by cleaning tests.
  • Keep spray stream moving across the masonry surface at a uniform rate at all times.
  • Shut off flow before stopping motion at the end of a sweep, and begin the sweep motion before opening flow.
  • Normal sweep motion is horizontal, side to side; however, a vertical pattern may be used where necessary.

CAUTION: “boring in” with spray should be avoided. Concentrating spray stream at a point; using too high of a pressure; and working at a less than approved distance, can seriously damage the masonry and may be cause for rejecting the work and reason to require additional repairs.

Low-Pressure and Medium-Pressure Water Washing:

  • Hand-brush and scrape heavy grime prior to washing (see Section 3.01 B. above).
    Take a common garden hose and power-wash the face of the building, gradually increasing the water pressure as needed to sufficiently loosen the dirt.

Allow to dry, and if additional cleaning is required, try the following:
Low-Pressure and Medium-Pressure Water Washing Supplemented with Non-Ionic Detergents:

  • Hand-brush and scrape heavy grime prior to washing (see Section 3.01 B. above).
  • Wash the masonry using a low-to-medium-pressure wash, adding a non-ionic detergent (see Section 2.02 A. above).
  • Hand-brush as needed with non-metallic brushes.
  • Rinse cleaned work with pressure wash spray as for cleaning to thoroughly remove loosened dirt, dirty cleaning water, and cleaner residue from surfaces.
  • Test rinse water residue on the masonry surface with pH indicating test strips regularly and record results in daily work log for review by RHPO.
  • Re-rinse/clean with clear water any area where the pH indicator strips show that there is residual acidity or alkalinity on the surface and allow to dry.