A.James Benney
responds: Pressure-washing is a good way to
remove dirt and loose paint, but you must use the
pressure-washer carefully. Add a mild degreaser
such as TSP to the water, and wait a day or two for
the walls to dry out before applying paint. Many
modern latex paints actually allow moisture to
breathe out through their dried film. If using oil
paints or stains, let the surface dry for an extra
day or two before application. The same holds true
for decks.
Remember that it is easy to do a lot of damage
in a hurry with a pressure-washer, especially to
wood siding and decks. Improperly handled, a
pressure-washer can gouge soft wood, drive water
into the interior of buildings (staining walls and
ceilings), break glass windows and light fixtures,
and injure the operator or someone nearby.
When pressure-washing wood siding that has
peeling paint, it is important to let the entire
surface dry and then scrape by hand. This is
because the moisture will also start to lift the
paint around the paint that was peeling. You
don’t want to paint over this compromised
surface, because it will be the first thing to
fail.
In California, all deck stains and sealers have
been reformulated to meet tough new pollution
standards, and this has affected surface
preparation. Many manufacturers now recommend that
decks be carefully pressure-washed in order to
remove all of the previous finish and to open up
the pores of the wood to accept the new sealer.
Then look forward to repeating the process every
couple of years.
James Benney is a member of
PaintCraft Associates, a guild of finishing experts
in the San Francisco Bay area.