Ask an Expert: Repair or Replace Damaged Deck?

: My house was built 20 years ago with a second-story redwood deck that is about 250 square feet. The deck has been stained, power-washed and decently maintained. But some of the deck joists and all four uprights have been diagnosed with dry rot/fungus and dry-wood termites. Should I replace the damaged joists and uprights or rip the thing down and start over? The deck faces south and west with views and is in full sun most of the day. I do not want to spend a lot of money if I can avoid it as I am semi-retired. The home is valued at about $1 million.

Answer: From Joe Wood of WoodsShop Creative Builders in San Diego, Calif.:

With an aged deck, you can sometimes retain the existing structure if it is sound, and it certainly makes sense to do so considering the higher cost of rebuilding. New decks can cost $50 to $75 per square foot or more.

If the rotted areas are only on the tops of the joists (the horizontal beams onto which the deck’s boards are fastened) and aren’t too bad, the damaged areas can be sealed with Termin-8 (a copper-based preservative) and then covered with joist flashing to prevent more water infiltration. One such product is Grace Vycor Deck Protector.

While you’re under the deck, you should also check the condition of any fittings and fasteners for corrosion.

When you replace the posts, use pressure-treated stock, and make sure you install them with an uncut, factory-sealed end down into the ground; don’t use a freshly cut end.

However, with all four posts and some of the joists showing signs of decay, there’s a very good chance the remainder of the joists will soon follow. Maybe it’s time to replace the deck with another that’s safe.

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