22 January, 2015

Deck Story

I was going through some old magazines recently and found an article from 2003 about a deck collapsing and killing about a dozen people in Chicago. It was a third-story deck and it broke loose where the deck framing met the building wall. Granted, there were a lot of people on it, but a plank called a ‘ledger board’ was partially rotted and it split where the bolts attached it to the building causing the collapse.

While there are decks that fail because they are not built to code specifications, the most common problem is that they are not maintained well. Often when a deck is refinished; the joists, ledger board, and posts have not been coated with waterproofing. Joists can remain wet for a long period of time--unable to dry because of shading by the planking above and they will rot. So, it’s vital to do an annual inspection and maintenance to a wood deck, especially older decks on long posts. Homeowners can do most of the maintenance required, but if the deck is more than 6 years old (or if you don’t know the age), a professional should do an inspection that specializes in wood-frame construction. This keeps your deck attractive, protects your investment and prevents a deck failure.

When I have built decks, I tend to over-build. If the design load is for 40 pounds per square foot and the span chart calls for 2x8” joists, I’ll use 2x10s. Where some plans may have one support beam, I will add a second beam or more (see the beam near the house wall in the drawing above). Use bolts and nuts with washers that go through the rim joist instead of nails or lag screws to attach the ledger to the house. Having lived in the NE Ohio Snow Belt my entire life, I’ve seen enough structures collapse with 3-to-5 feet of wet snowfall (often at the ledger board) and I just don’t want that beggar to come down. 

It is important that railings are well secured and the spacing (4 inches) between balusters to prevent small children slipping through the railing. The stronger the deck is, the less likely Junior’s graduation party will bring it down, too.

So you may consider adding an extra beam under your deck to strengthen it.

Check the understructure to ensure the wood is solid. If you can push a screwdriver a quarter-inch into the wood, it’s time to replace it. Do the same test with the deck planks, too. If you replace any rotted planks, use galvanized or stainless steel screws instead nails to prevent the plank from pulling up.

You will need to clean the deck before refinishing a deck. A pressure washer alone will clean the deck to prepare it for refinishing if you do not wish to use chemicals. But if it is a long time between refinishes, a commercial deck cleaning solution with oxalic acid (wood bleach) may be necessary to remove the dirt, gray coloring, mildew, and stains. I found that using a garden sprayer to apply the cleaning solution and then using a scrub brush mounted on a broom handle to clean the surface works well. Grease stains (under an outdoor grill, for example) are tough to get out; a paste of TSP (Tri Sodium Phosphate) scrubbed into the stain will break up a lot of it. The pressure washer is then used to finish cleaning.

Let the wood dry for a few days before applying the finish. You can use a color stain water seal on the visible surfaces, but all the surfaces of the understructure should be treated with the clear water seal to prevent decay, especially the support beam and posts.

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