Deck Post Safety- Is your Deck Supported Correctly?

Deck Post Safety- Is your Deck Supported Correctly?


We want deck owners to have safe structures to enjoy with family and friends. There are many aspects of deck safety home owners can inspect on a regular basis.  The more attention you pay to the condition of your deck, the better.  Keep your family and guests safe by performing yearly inspections for deck safety.  This blog outlines how to inspect one of the most important structural feature of your deck: the deck posts.


Why are Posts Important?

Think about how hard it would be to stand without legs.  Literally, no legs to stand on.  Deck posts support the beams, which provide support for joists.  That’s a lot of support.  The important thing to know is that posts create the desired elevation of a raised deck.  Deck construction starts with installation of posts.  The size, spacing, and footing of the posts play important roles in the overall safety of your deck.

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Post Size

There are quite a few details to know when evaluating the safety of deck posts.  First, determine if the posts size is large enough to support the structure.  Builders use 6×6” posts for decks.  If your posts are 4×4”, they are probably too small and may affect the overall strength of the deck.  This is especially true of high sitting decks.  “Tall 4”x4” posts twist under load and 4”x4” posts, even when treated, decay below grade to quickly,” (Gromicko).



Next, look at how far the posts are spaced from each other.  Wider decks require more posts to support a longer spanning beam.  In general, builders space posts no more than 8 feet apart.  Also, the size of your joist material determines the maximum distance between footings.  Most decks use 2″x8” or 2″x10” sized joists.  However, in rare cases, decking spans across 2″x6” or 2″x12” joists.



In addition to size and spacing, inspectors evaluate how the posts were installed in the ground.  Common mistakes include not using concrete, not attaching the post to its footing, and using pre-cast concrete piers.  The way the post is attached to the footing affects the overall strength of the structure.  Posts should be directly connected to the footing.  This eliminates the chance of the post lifting or sliding off the footing.


Water Threats

Nearby moisture threats also threaten the durability of your deck posts.  Avoid installing posts in close proximity to downspouts and sprinkler systems.  Moisture causes pressure treated wood to decay over time.  Constant contact with water contributes to post decay.  Inspect the bottom of the post by pushing your fingers against the base to check for soft spots.  If the wood feels damp and soft, or worse, the wood caves in as you apply pressure, your posts are decaying.




Gromicko, N. “Inspecting a Deck, Illustrated.” International
Association of Certified Home Inspectors. InterNACHI, 2006-2018.

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