Wood Deck Collapse


Written by Chris Carlson, PE

A heightened concern over residential wood deck failures has become prevalent with the recent collapses in the DC – Baltimore area and with the arrival of warm weather.

https://wtop.com/howard-county/2018/09/8-injured-after-deck-collapses-in-ellicott-city/slide/2/

https://wtop.com/montgomery-county/2019/05/deck-collapse-in-germantown-md-injures-at-least-2-adults/slide/1/

Several hundred injuries occur each year due to deck collapses according to published statistics.  So, this is not a new phenomenon.  The Building Code and local jurisdictions have required special details for connecting decks to buildings for many years. Often a lack of flashing or poorly installed flashing is to blame as, over time, water infiltration can result in the decay of the wood framing hidden behind the siding to which the deck is attached.  We have also seen decks connected improperly (too few fasteners, improperly spaced fasteners) or to wood framing that lacks sufficient strength.  Proper flashing and adequate structure must be present to ensure a well secured deck for the long-term.

FEMA has published this detail in their Coastal Construction Handbook for many years, which shows a robust flashing system.

https://www.fema.gov/media-library-data/20130726-1537-20490-9609/fema499_5_2.pdf

Unfortunately, not all decks have not been installed with proper fasteners and flashings.  So, we will likely continue to see these collapses from time to time in the news.  Montgomery County, Maryland officials have provided this checklist for annual deck inspections of residential decks by homeowners.

https://www.montgomerycountymd.gov/DPS/Resources/Files/RCI/Deck-Maintenance.pdf

It is a good practice to make an annual inspection of your wood deck, especially if it is 15 or more years old.