Galvanized screws leave ugly blotches on cedar deck


July 25, 1992|By Karol V. Menzie and Randy Johnson

It's often the littlest things that cause the biggest problems around the house. That's certainly the case for a New York state reader who's having a problem with galvanized screws.

The offending screws are in a newly constructed, 1,300-square-foot, tri-level deck. The homeowners were so concerned about preserving the beauty of the deck that they asked for cedar, rather than pressure-treated wood, and for screws, rather than nails, "to avoid unsightly 'nail-pops.' "

"Our contractor did a beautiful job constructing this deck, and we were quite pleased with its initial appearance," the reader writes.

"Within a few months, however, black blotches began appearing around every galvanized screw that was used in the construction. Many of these blotches are quite large and have made a 'magazine cover' deck into an unsightly nightmare."

Despite pressure-washing, application of a commercial 'wood brightener' and of a preservative, the blotches have returned. "During our course of trying to 'fix this deck,' " the homeowners write, "we learned that when galvanized screws are used with cedar wood, a chemical reaction occurs" and causes the blotches. "Our contractor admitted to being aware that this could happen, and said that our alternative would have been to use stainless steel screws. Unfortunately, he never in formed us of this initially, or we would have insisted on using stainless steel screws."

The reader wants to know three things: Can the blotches be cleaned again, despite the preservative; can anything short of replacing the screws prevent the blotches from returning; and is the contractor responsible for fixing the problem.

The first two answers are easy, if not entirely welcome.

The blotches are caused by the interaction of resins in the wood with iron in the screws, says Kip Humphrey, of Deckcraft Inc. of Pikesville. The problem is called "tannin bleed" in the trade, Mr. Humphrey said, and it happens because the galvanized-metal coating on the nails or screws is inadequate. Nails can be "hot-dipped," or dunked right in the galvanized metal, to be coated, but screws can't; it would gum up the threads. So screws (and cheap nails) use a powdered galvanized coating that is electrostatically applied. When you hit one with a hammer or drive it with a screw gun, it's likely that the coating will chip, the resin will reach the iron, and blotches will form.

The only way to avoid the problem with screws is to use stainless steel or bronze, Mr. Humphrey said.

The commercial wood brightener the homeowner used was oxalic acid, and he believes it will work over the preservative seal, but it's "a "temporary fix," he said. (The homeowner could check with the sealer manufacturer to be sure.)

"The only permanent fix," Mr. Humphrey said, "is to replace the galvanized screw with bronze or stainless."

Mr. Humphrey noted that stainless steel screws are three or four times as expensive as a galvanized screw, and bronze screws are twice as expensive as stainless.

The question of whether or not the contractor is responsible for fixing the problem is a little more complicated.

To start with, what did the contract say? If you specified stainless steel screws and the contractor used galvanized ones, you'd have a clear case. But if the contract is not specific, the contractor's moral obligation to warn you about the screws is unclear. Consider it from a contractor's point of view: Would you have hired this particular contractor if his bid was considerably higher (to account for the cost of the screws)?

In these recessionary times, many contractors are unwilling to suggest a client pay more for a job, even it means doing it the right way, because they could easily lose the job to a lower (and even less concerned) bidder.

In this case, the original contractor should be given an opportunity to remedy the problem. Good contractors want happy clients who can give them favorable references for future jobs. Call him or schedule a meeting to see what he's willing to do.

If for some reason the contractor is reluctant to proceed, the next step is to check with the closest regulating body. In Maryland, it's the state Home Improvement Commission, which licenses contractors and provides free arbitration in disputes. The Better Business Bureau may also provide free or low-cost arbitration; check with the local chapter.

If those options won't do, don't decide to escalate the dispute without doing a "cost-benefit analysis." How much will it cost to have the deck cleaned and the screws replaced? Consider getting another bid for that. It may be a lot less expensive, in time and money, than hiring a lawyer.

Next: Tips on maintaining a deck.

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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