Did you know that thousands of decks collapse each year? Or 224,000 between 2003-2007 to be specific? Here is the study: http://www.buildingonline.com/news/pdfs/Outdoor-Deck-and-Porch-Injury-Study.pdf
Did you know that improperly built decks result in hundreds of deaths each year?
Did you know that a deck is the one job that every “contractor” with a toolbox thinks that he can build?
Do you want to ensure that your deck will not collapse? Let's walk through a few of the steps briefly to ensure that you are taking the actions required so that your deck will not end up laying on the ground by the end of summer.
What is a ledger?
The number one cause of deck collapse according to InterNachi is a the ledger board pulling away from the band joist.
Are you following me?
Probably not. Let me explain.
The ledger board is the board that connects the deck directly to the house. This is where the rubber meets the road in terms of deck connection. The ledger board is attached directly to the house’s band board. Refer to image:
The Ledger board attaches directly to the bank board located on the other side. However, it’s important that the connection is solid and numerous: we want to see many ½” bolts and hangers on each deck floor joist.
Now, we can see clearly why a separation here could spell doom for your favorite outdoor space.
As inspectors, this is one of the first places we look when we examine the structural integrity of a deck. There are no areas that can afford to be weak in terms of structure, but as the main cause of failure this particular area typically is the highlighted concern.
What can go wrong with this board? Several things, but flashing is often an issue. Flashing is the material installed at the point of penetration, where the two boards make their connection and thus force a hole in the exterior of the house. In the image below, the silver pieces of metal located above and below the ledger are the flashing. The purpose is to divert water that ordinarily simply flows with gravity and finds the lowest point. As rain falls, the flashing serves to “protect” the point where the board penetrates the exterior and thus keep water out of this delicate space. If water is allowed in over time, the boards will become weak, rot will likely occur, and rotten boards cannot support the weight of your family on your deck.
What else may cause the ledger to be considered a “defect”? Not enough 1/2 “ diameter bolts and joist hangers. This is more of a cause of concern for older decks built decades ago, but even today we still find decks that have been built improperly by the insufficient amount of connections. See the proper image below:
Now, let’s be honest. Does everyone’s ledger look like this? No. Mine doesn’t, and that’s ok. We would rather err on the side of caution as opposed to having not enough support, but as long as the deck ledger appears in good shape, is properly flashed and shows no sign of wood decay then we can get away with not having an excessive amount of bolts. But we do not want to see something like this, though we often do:
Notice not only the location of the bolts (center of the board as opposed to staggered) but the amount.
Keep this area in mind the next time you step outside and stride across your deck. This board carries the weight of the deck and of the people on the deck, the nearer they stand to the outside exterior. Installing a new ledger if needed, or simply better securing the one that you have now, will save time, money, and hospital bills.
We will look at other areas of concern next time!
Spencer Brothers, CPI
Sterling Home Inspection, LLC.