Deck safety research at Virginia Tech
Professor Joseph Loferski of the Department of Sustainable Biomaterials has been conducting research on the structural engineering of residential decks and balconies for more than two decades and has been a major influencer on the development of building codes that keep people safe. In March 2021, Dr. Loferski presented a lecture to the College of Natural Resources and Environment’s Third Thursday Lunch and Learn webinar. In his presentation, Dr. Loferski presented the results of decades of research that has been conducted at the Brooks Forest Products Center - Wood Engineering Laboratory, and he identified numerous items for home-owners to look for on their own decks to improve their safety.
In the United States, the collapse of wooden decks, balconies, and exterior railing systems have become a significant safety hazard. Most deck related accidents are either caused by failure of the deck-to-house connections, or the failure of the deck guardrail system. Because many people occupy these structures during outdoor events, a structural failure often results in serious injuries. When the deck–to-house connection fails, the deck collapses catastrophically resulting in serious injuries or death. The failure of a deck guardrail can cause people to fall from the deck to the ground and also often results in serious injuries.
Dr. Loferski informed webinar attendees that the main reasons for deck failures are: 1) insufficient fasteners, 2) improper materials, 3) construction defects, and 4) decay of wood. To ensure the safety of decks, each component must be considered as a part of a system and designed considering the characteristics of the entire system. Loferski presented the results of structural tests of the deck-to-house connections. He also covered the required spacing and locations of bolts or lag screws that attach the deck to the house; if these requirements are followed, deck collapses will become a thing of the past!
Loferski also presented the guidelines for deck guardrail systems including the need for a 36-inch height and a maximum picket spacing of 4 inches or less to keep children from falling through the guardrails. He also showed the results of testing common guardrail post connections and the need for special connectors to safely carry the loads placed on a guardrail.
Dr. Loferski said that several publications are available on safe deck construction including the free publication from the American Wood Council Design for Code Acceptance-6 (DCA-6) that shows the correct methods to construct a deck and includes the results of Loferski’s research. Homeowners can use this document to inspect their own deck or to show to a builder during the construction of a new deck.