Is Your Deck Safe?

Outdoor living became popular starting around 1980 and continues to grow in popularity.  There are an estimated 60 million decks in the US.  Statistics also show that from the years 2010 to 2014 there were an average of 7,700 people each year that went to a hospital emergency room after a structural failure on a deck, porch, or balcony.

When I am out and about inspecting homes, one of the most common questions on the exterior is: “How long do you think the roof will last?”.  But no one has ever asked “How long do you think my deck will last?”.  According to a technical report from Forest Products Journal, a pressure treated deck only last 9-10 years due to the effects of cycling from wet to dry.

Deck Construction 

To understand whether your deck is constructed safely, one must understand the components.  Most decks consist of Posts and Beams, Joist, Ledger boards, Deck boards, Guardrails, Stairs, and Stair/Hand Rails.  The manner in which these components are installed are vital in determining if the deck is constructed in a safe manner. 


In the image above you can see all of the components of a standard deck.  (I might add that in this image the post to beam connection is incorrect.)  The standards in which decks are to be constructed have changed over the past few years.  Most notably the connection of the post to beam and the manner in which the guard rail posts must be connected to the deck framing members. According to NADRA, (North American Deck and Railing Association) all decks should be inspected on an annual basis for signs of failure and safety violations.  I’ll go through some common issues I find on a regular basis here.

  • Ledger Board Connection

One of the most common “major” violations I find is the connection and installation of the ledger board.  When the homes exterior wall is used as support for one side of the deck, certain standards must be followed to avoid fastener pull-out and moisture intrusion issues into the box sill of the home.  Sometimes I find the ledger board only nailed with 16d common nails.  This is inadequate and would likely pull out and result in deck collapse.  The ledger must be bolted to the rim joist of the home using lag bolts or lag screws.  These fasteners must be approved for this application.  The other violation that is common is the fastener spacing.  These fasteners must be no more than 32 inches on center, and be in a staggered pattern.

Another important component at the ledger is the flashing.  This flashing diverts water over the board to eliminate moisture from penetrating the wood.  This flashing also prevents water from running behind the ledger board which many times ends up following the fasteners into the rim joist and can cause moisture intrusion issues into the box sill.

One more thought on the ledger connection.  If you are checking your deck and find red rust on the fastener head, it should be replaced.  When a bolt shows this condition up to 70% of the fastener strength can be lost because the most damage is likely hidden from view.

  • Joist and Joist hangers

All joist must be supported by joist hangers at the ledger board.  One common defect found in this connection is the use of unapproved fasteners.  Lag screws, drywall screws, roofing nails, zinc coated or uncoated nails are not acceptable for outdoor, structural connector applications.  It is recommended to follow the joist hanger manufacturer recommendations for the correct fasteners.  Also I should note that ALL fastener locations in the hanger must be used, there are no exceptions to this rule.

  • Post and Beam Connection

In the past many builders would run the post up and sandwich it inside the beam by basically through bolting 2 2×10’s on the sides of the post.  This was an acceptable practice up until a few years ago.  The reason this is not allowed is because there is not enough shear strength in the fasteners and the code officials want to see beam bearing to provide adequate support for the beam.  If your deck was built in this fashion, don’t worry, there is a Simpson Strong Tie bracket that can be installed to provide this bearing.  Another common issue with this connection is with post notching.  If your deck support posts are 4×4’s and exceed 6 feet in length please consider having them replaced.  These posts tend to warp and twist during the drying process which can make the connections unstable.  Often times these posts are notched and then the beam is bolted, this does not allow for enough cross sectional area at the top of the post and more times than not, splitting within the post will occur.  If this cracking exceeds 12 inches, the post will need replacement.  4×4 posts are only allowed to be notched up to 3/4 inches and 6×6 posts are only allowed up to a 1 3/8 inch notch so as you can see this does not allow for a beam connection anyway.

Deck Beam Bracket
  • Guardrails

Guardrail construction has also changed over the past few years.  Generally 4×4 posts are used for guardrail support. Wait, what?  your deck doesn’t have posts as part of guardrail support?  You likely have a safety issue on your hands, all guardrails must be supported by posts.  Balusters (spindles) cannot be counted on to provide the 200 pound point load required.  There have also been many rule changes with regards to baluster spacing.  Current building standards state that a 4 inch diameter sphere should not be able to pas through the space between spindles.  This is a matter of child safety.  Some decorative balustrades also create this safety hazard in their designs.

So, as you can see there are a lot of areas of concern when it comes to deck construction.  Deck failures is one of the most common sources of injury causing accidents at home.  I only touched on a few of the most common issues found during home inspections.  and I didn’t even get into stairs, handrails, and stair rails.  Maybe next time.

A key element to enjoying your deck for years to come is making sure it is safe for your family, friends, and special family events such as birthday parties, graduations and weddings. In the interest of deck safety, homeowners should inspect their decks frequently and consider a professional deck inspection at least yearly.

As a new member of NADRA it is my intention to bring awareness to safety issues with outdoor living spaces as well as handrails, guardrails, and stairs.  Dealing with this Covid virus is bad enough, it would sure be harder to get our masks on with a broken arm from a deck collapse.  In the near future we will also have a new service offering for homeowners who wish to have their decks inspected for safety issues as well as normal age related issues.  So stay tuned for that.

As always, I hope I have provided some value with this post and if you have any home related questions, don’t hesitate to hit me up at: 



Aaron M. Zuehlke is the owner and inspector at Zuehlke Inspection Service, LLC, a full-service home inspection company serving Southern Wisconsin. Specializing in Home inspection, Radon Testing, Mold Testing/inspection, Residential Thermal Imaging, and Manufactured Home Foundation Certifications. He also manages several rental properties through Zuehlke Properties, LLC. He can be reached by email at or by calling the office at 608-931-7485.

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