Your Place: Readers suggest reasons the cedar deck rotted

I'll let my faithful and informed readers have a go at this week's column, since they've offered some useful insight into problems for which I've requested feedback in the last few weeks.

A reader had asked why his cedar deck rotted after eight seasons.

He had waited several months after the deck was built to paint it with a semitransparent stain. Several months after that, the paint began to peel, and in the years since, he has repeatedly repainted it with the same result.

I offered a few possibilities from my own experience with cedar and asked for others.

Paul Mackie, Western field representative - also known as "Mr. Cedar" - for the Western Red Cedar Lumber Association, identified three factors that might have contributed to the premature failure.

First, repeated application of a film-forming finish (like stain) traps moisture. This can result in the finish flaking or peeling, or even accelerated decay.

The association recommends oil-based stains, which are better absorbed by Western red cedar. Finishes recommended are available in transparent and tinted or lightly pigmented formulas and should contain mildewcides that help control mold and mildew growth.

Completely transparent stains should contain ultraviolet filters that offer some protection against UV damage.

Second, Mackie says a stain should be applied immediately. Leaving the deck exposed to UV for even two weeks can result in photo degradation, which would be another factor in the adhesion problem.

The wood does not need to age or cure.

Last, the manner in which the deck was installed could have contributed to its decay. If the deck boards were installed too tightly, edge-to-edge, it would have prevented proper drainage and not allowed the deck to dry. Or, the deck could have been installed without proper ventilation underneath. This traps moisture too.

Susan Kowalski, a Chicago-area reader, said she and her husband used stain made by Behr within a month after their deck was built, and have had the same problem as the reader I wrote about. They followed the directions the manufacturer sent, without success.

"This year, we powerwashed it, put Thompson's WaterSeal on it, and watched as our beautiful cedar deck turned gray, just like the less expensive decking."

Patricia Keller of Lancaster has had to deal with wood rot over the last 34 years that she and her spouse have lived in their home.

"Unlike the past, I feel that wood today is not being aged properly, and inferior wood is being [presented] as good quality," she said. "I think there is more to this problem than improper painting or staining."

Paul Grens of Connecticut also had his cedar deck rot after eight years. The boards were painted at the lumber supplier. He painted the top a few times with oil base, but believes the rot occurred below the surface.

"I noticed most of the rot occurred where the boards lay on the vertical pressure-treated joists. When I removed them, the top of the joists were soaked with water."

He replaced a third of the deck, and ran a silicone layer of caulk on the dry joists before installing the boards.

"It's been four years now, and I will keep checking for more rot," he said.

Finally, Huck DeVenzio of Arch Wood Protection in Atlanta says the longevity of cedar depends on the grade of the wood. If the cedar comes from the center of a tree and is primarily heartwood (where wood is most dense and natural decay-resisting chemicals concentrate), the wood has greater resistance to rot than if the lumber is a less expensive, sapwood grade.

"Generally, it is not colorant in stain that helps protect wood, but the presence of water repellent," he said. "Prompt application is a good idea when the stain contains water repellent. If it does not, then there is less urgency since the stain will mostly color the wood rather than protect it."

As always, thanks for your advice.

This week, Al Heavens shows how to remove a screw with a damaged head at philly.com/yourplace.EndText