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 and organic dirt/dust.
damage and mold growth 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
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
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.,
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