New treatment of wood preservative is 'like sunscreen for the deck'


Most people these days know better than to sit outside in the broiling summer sun with no protection. And surely nobody would sit outside in the winter with absolutely nothing between the skin and the rain, sleet, snow and cold.

So why are you expecting your deck to do both of those things?

It's an investment that deserves protection. The average deck costs $3,000 to $8,000, says Bob Franklin, president of Deck Doctor of Reisterstown, which builds and restores decks. "People think treated lumber will last for 40 years," Mr. Franklin says. The truth is, "decks don't last forever."

The chemical preservatives that are forced into the wood -- that's the "treating" part of treated wood -- need to be renewed periodically.

"Decks are weathered by water and UV ultraviolet sunlight," says Kip Humphrey, owner of Deckcraft Inc. of Pikesville. "That gray, washboard, weathered look means the wood is drying out." Treating the wood to a new round of preservative is "kind of like sunscreen lotion for the deck," Mr. Humphrey says.

Mildew, mold and rot also take their toll on treated deck wood.

A regular maintenance program is the only way to keep a deck from damage. The process is not so complicated that a reasonably handy homeowner can't do it, though it would probably be better to hire a professional if the deck needs treatment with a "power-washer." The power-washing device forces water under high pressure through a wand; if it's not used correctly it can blast away the softer tissues of the wood and leave the harder edges -- the grain lines -- sticking up. Those edges can be "as sharp as razors," Mr. Humphrey says -- not at all nice to walk on.

There is some controversy over how soon to treat a new deck. Mr. Franklin says the wood has aged sufficiently at the lumber mill, and there's no reason not to treat it immediately. Mr. Humphrey says the only thing wrong with treating the deck too soon is that the treatment may not last as long as it otherwise would; it just means you'll have to schedule the next maintenance treatment sooner.

The ideal preservative product, Mr. Humphrey says, includes a UV blocker, oils to replenish the wood and a moisture sealant that works by penetrating the wood. When he builds a deck, he lets it "age" two or three weeks, then power-washes it, lets it dry out for three to four days, then applies the sealer.

Homeowners with new decks who don't want to power-wash, or don't want to wait four to six months for natural aging, could sand the deck before applying the preservative.

If your deck has gone more than five years without being treated, it's too late to worry about UV protection or penetrating oils; the battle against aging has already been lost. At that point, only the water-repellent factor is important.

"Don't seal a dirty deck," Mr. Franklin says. Professionals clean with power washers and specially formulated deck cleaners. Do-it-yourselfers who want to avoid the power washer can use the deck cleaner and simply hose it off. Some cleaning products have a mildew killer; if you have mildew, don't apply a preservative without killing the mildew first.

Here are some deck maintenance tips from Mr. Humphrey:

*Clean the deck on a regular basis -- as often as four times a year, and more often if there's heavy tree-staining.

*When you use a cleaner, wet down the deck and surrounding trees and plants. (Water will keep the alkaline cleaners from sticking to plant leaves and damaging them. Mr. Franklin suggested also masking off the house with plastic to protect it from overspray.) Mop on the cleaner, let it sit for 10 to 20 minutes, then hose it off.

*Decks can be protected with paint or stain, which will also protect the wood from weathering. Stains probably last longer than paint, but an area that isn't walked on -- such as railings -- will do fine with paint. Painting or staining it may be the only way to "renew" a neglected deck.

*Before you buy a preservative product, be sure to read the label carefully. Make sure it contains everything the deck requires, and the

application fits your needs. Some preservatives can be sprayed on, some can be brushed on.

However you apply it, be careful to put on one coat only. Don't go over any area repeatedly and "don't let it puddle," Mr. Humphrey says.

Note: Last week we answered a reader's question about stains in a deck caused by galvanized screws. The problem occurred because the deck was made of cedar. The iron in galvanized nails and screws reacts to tannins in the cedar and causes black blotches. But galvanized nails and screws are fine in pressure-treated wood.

Next: Answers to readers' questions.

Mr. Johnson is construction manager for Neighborhood Housing Services of Baltimore. Ms. Menzie is a home writer for The Sun.

If you have questions, tips or experiences to share about working on houses, write to us c/o HOME WORK, The Sun, 501 N. Calvert St., Baltimore 21278. Questions of general interest will be answered in the column; comments, tips and experiences will be reported in occasional columns.

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