PCI Note: Mold spores and organic dirt and dust landing on exterior siding, roofs, and concrete/brick/block/masonry surfaces enable mold to grow on those surfaces. Read the helpful how-to article below about pressure washing, which if done on a routine maintenance basis, can get rid of the build up of mold spores, mold growth, and organic dirt and dust.

Prevent building damage with pressure washing
by Bill Griffin, cmmonline.com June 1, 2004

All building surfaces will deteriorate and require maintenance over time to prevent premature failure and internal damage. Pollutants from industry, the atmosphere and combustion have increased the need to maintain the building envelope.

Regular cleaning and maintenance not only enhances the appearance of a building and prevents damage, but it also helps in delaying the need for expensive, and time-consuming restoration, repair or replacement of building materials.

Pressure washing it clean

Many contractors use high or low pressure washing systems to clean building exteriors. The system is effective on a wide variety of surfaces and quite productive, which helps reduce high labor costs associated with other manual cleaning processes.

Most contractors agree that pressure-washing systems are more efficient at cleaning brick, stone and concrete exteriors.

In many cases, high-pressure water without any special cleaning materials will successfully clean masonry surfaces.

High-pressure cleaning may be used on most hard, textured clay brick; this includes reds, buffs, grays and other through-the-body colors.

However, it is safest to keep pressure well below 1000 PSI when cleaning buffs, grays, etc., since these colors are more susceptible to mineral oxidation, which could be aggravated by excessively deep penetration of water.

High-pressure water cleaning can damage soft brick or stone and erode mortar joints: Keep the pressure low and the nozzle tip a safe distance from the surface to avoid damage.

Basic pressure washing procedure in 11 steps:

1. Inspect the structure and surface for needed repairs, special cautions or treatment prior to cleaning.

2. Tape with plastic adjacent metal, glass, wood, etc. surfaces as required to prevent damage or exposure to harsh chemicals.

3. Test clean an area and let it dry before inspection, approval and proceeding.

4. Pre-wet/saturate the masonry surface with water before cleaning. This includes all immediate areas to be cleaned, as well as areas below and adjacent to the area being cleaned.

5. When cleaning soft brick, be sure to soak the surface heavily with water before applying a cleaning solution. Use a surfactant cleanser so that the cleaning chemical will stay on the surface of the brick and remove the soil.

6. Mix the cleaning solution. Use the concentration level that is recommended by the manufacturer.

7. Once the surface is completely saturated with water, apply the cleaning solution starting at the top of the wall or area. Cleaning solutions may be applied effectively and safely by brush or a low-pressure sprayer (maximum 40 PSI).

8. Let the cleaning solution dwell on the surface for 5 to 10 minutes or as directed on product label. Agitation with a brush may be needed.

9. Rinse the surface with high pressure water from top to bottom so all dissolved soil and particles will be completely flushed from the surface.

10. Inspect your work and redo as needed or proceed as appropriate.

11. Remove tape and plastic from windows, wood and metal areas, shrubbery and adjacent areas.

Bill Griffin is president, Cleaning Consultant Services, Inc., Seattle.

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