The appeal of natural wood siding is hard to deny. Its beauty
has highlighted many a
new home.

In Georgia’s humid climate, though, mold and mildew can turn
wood’s warmth and beauty
to a dirty-looking, splotchy gray. Some people begin to wonder
what they ever liked about
wood.

But the wood’s beauty doesn’t have to be lost.

"Over time, all unfinished wood, exposed outside, will
develop a soft gray patina
because of ultraviolet light in sunlight," said Julian
Beckwith, a wood products
specialist with the University of Georgia Extension Service.

"That blotchy look that’s so unattractive," he
said, "is caused by mold
and mildew that results from uneven wetting by rain and
dew."

Keeping wood siding and decks looking like newly cut lumber
forever is nearly
impossible, he said.

Some clear finishes will slow the process of graying, and
many contain preservatives
which reduce mold and mildew growth.

"These finishes aren’t very durable," Beckwith
said. "They have to be
reapplied every year or two."

Chemicals that block ultraviolet light are being added to
newer clear finishes, making
them a more attractive alternative than before, he said.

"But a good water-repellent preservative, especially one
containing ultraviolet
inhibitors, is probably the best thing available to date,"
he said.

Longer-lasting protection is available, though.

For a finish that can last as much as 10 years on rough-sawn
siding, use two coats of a
"semitransparent" (lightly pigmented) stain containing
mildewcides and
water-repellents, Beckwith said.

These stains come in attractive colors, some even providing
the look of fresh-sawn
lumber.

For long-lasting finishes on smooth siding, apply a
paintable, water-repellent
preservative first, he said. Then apply an acrylic latex primer
and an acrylic latex or
solid-color stain as a topcoat.

Over the life of siding finishes, he said, periodic washing
with soap and water can
greatly brighten their appearance.

If mold and mildew have accumulated, you may need to use a
bleach solution to remove
them.

"Besides restoring its beauty, a good cleaning can
increase the life of the
siding, too," Beckwith said.

The best cleaning solution for weathered, mildew-stained wood
includes six to 10
tablespoons of trisodium phosphate and one cup of bleach in a
gallon of water.

But Beckwith said common household detergents and bleach will
work, too. If you use the
latter, though, follow the instructions on the bleach label
carefully — mixing chlorine
bleach with some cleaning agents can release poisonous chlorine
gas.

After cleaning and bleaching, rinse the wood surface
thoroughly and allow it to dry.

If you’re applying a new finish, be sure to brush, scrape or
sand any peeling or
flaking old finish before you do, he said.

"Using the right finish and cleaning it from time to
time should keep you from
having to refinish it often," Beckwith said. "The
pleasure of wood siding
doesn’t have to be a high-priced luxury."