Exterior Wood Deck Failures: An Almost Certain Multi-Claim Event

Richard Rice

4,600 emergency room visits were associated with deck collapses between 2003 and 2015 and another 1,900 with porch failures.

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Imagine you have a barbecue at your residence for approximately 60 people. Because it’s a beautiful day, you decide to bring the guests, table settings and caterers – with their open-flame Sterno cans – onto the 11-foot-high exterior wood deck. At 6:00 p.m., the dinner bell rings, and all gather in front of the serving table. Without warning, the deck detaches from the house and collapses. Sixty people are now piled on top of each other on the ground below. While no one dies, every single person has an injury of some kind requiring medical attention, from broken bones to severe burns. One person suffers from a broken neck and now has quadriplegia.

As you can see from this true, terrible story, poorly constructed and maintained wood decks can easily fail, resulting in serious injury and even death. A Consumer Product Safety Commission analysis estimated that 4,600 emergency room visits were associated with deck collapses between 2003 and 2015 and another 1,900 with porch failures.

Moreover, this type of event can result in dozens of claims for thousands of dollars in damages as well as possible litigation. Performing a complete and thorough investigation and determining the causes of exterior wood deck failures is essential for maximizing subrogation potential.

Problems with Deck Construction and Maintenance

Properly designed, constructed and maintained exterior wood decks should not fail as often as they do. For decades, decks have been designed for a minimum live load (i.e., people and things) of 40 pounds per square foot (PSF). For clarity, a 3-by-3-foot area (9 square feet) should be able to hold a person who weighs 360 pounds (9 square feet x 40 pounds = 360 pounds). In other words, people crowding together on a deck should not make a difference from a design perspective.

Unfortunately, it is when unskilled, inexperienced “carpenters” are allowed to improperly construct decks that problems occur. Decks are usually an afterthought of the contractor and are not given proper attention. Additionally, property owners habitually do not appreciate the large amount of environmental exposure a deck encounters over the years and often fail to adequately maintain the structure.

Even when a property owner is conscientious and has the deck inspected, the inspector does not often search for hidden problems. In the earlier example, the policy holder astutely hired an exterminator prior to his barbecue to inspect the doomed deck for insect infestation and other problems. Even though the ledger board connecting the deck to the residence was grossly decayed from insect infestation, the exterminator gave a clean bill of health.

Causes of Exterior Wood Deck Failures

Improper Fastening. A wood deck can fail if the ledger board is not properly attached to the main structure. Nails should never be used to attach the ledger board due to the tendency of nails to pull out from the wood. Instead, current building codes allow for the use of lag bolts, or through bolts. Lag bolts are the only allowable way to fasten the wood ledger board, and they must be long enough to connect the ledger board to the main structure securely. Because lag bolts can only be seen from the exterior, it’s difficult to determine if lag bolts are the correct length. As a result, inspections might miss deficiencies in this area.

Missing Metal Flashing. Wood deck failures can also occur if ledger boards are not properly protected from the environment. Proper installation of metal flashing over the wood ledger board is essential to preventing rainwater from entering behind the exterior wood siding. Without metal flashing, there is nothing to prevent water from rotting the wood behind the ledger board. Even with the use of lag bolts to fasten the ledger board to the main structure, rotting wood does not provide enough stability for the lag bolt to grip and can result in failure.

Investigating Deck Failures to Maximize Subrogation Potential

Circumstances surrounding deck failures vary from case to case. However, there are things in every situation that must be done to perform a complete investigation. They are as follows:

  • Do not let the property owner move the deck, replace the deck or alter the scene in any way until you or your engineer can document the scene.
  • Tell your policy holder to take as many photographs as they can immediately after the deck failure, before family, friends, pets, weather and well-intentioned neighbors can alter the scene.
  • Interview the witnesses as soon as possible. What were the people doing? Were they dancing? What kind of music was playing? How many people were on the deck?
  • Thoroughly interview the property owner. How old is the residence? Was the deck original to the residence or built later? When did they move in? Was there a property inspection performed prior to closing? Was the property ever a foreclosure taken over by HUD (HUD hires special inspectors to inspect a property)?
  • Hire a licensed Professional Engineer who is not only experienced in deck design and construction but also a Forensic Engineer familiar with proper evidence protocols.

Depending on the situation, subrogation potential could lie with the following parties:

  • Property/deck owner
  • Building contractor/subcontractor
  • Deck material supplier
  • Real estate agent
  • Design Engineer
  • Home inspector (privately- or government-hired)
  • Exterminator

Getting to the Root of Deck Failures

Wood deck failures happen more often than they should and have the potential to create many claims for the insurance professional if the policy holder is the owner of the deck at the time of the failure. A timely and thorough investigation can help uncover the true causes of deck failures and most likely produce other players for potential subrogation.

Jensen Hughes’ team of forensics experts have a deep understanding of all aspects of building design and construction, condition assessment and evaluation techniques as well as proven experience in multi-component and materials failure analysis, root cause analysis, litigation support and expert testimony. Learn more about how we can assist with your investigation.

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About the author

Richard Rice
Richard Rice is a Senior Civil + Structural Forensic Engineer experienced in consulting for civil and structural forensic engineering projects throughout the US and Mexico.

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