I replaced the pressure-treated lumber on my 1990 built deck and it matched what was there. The 4x4 rail post spacing width is 7 feet apart. I noticed recently that rail post spacing should be 6 ft or less. Am I grandfathered in if all I did was replace my weathered wood with new wood? I live in NJ. I looked at an article "recently" and it stated that posts should be 6' apart or less when building a deck. On my old deck, after taking out the old lumber I inspected the foundation and support wood and it was all in good shape. I replaced the 2x6 flooring, 4x4 railing posts and 2x2 balusters with new wood. Put it all back as "it was originally" (7 ft 4x4 railing post spacing). So my question is since my deck is not a new deck am I grandfathered in to the 7' rail post spacing?

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    How would we know? You haven't even told us where you you are or what code you seek to comply with. What exactly did you "notice recently"?
    – isherwood
    Commented Nov 2, 2021 at 16:57
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    Deck of Theseus Commented Nov 2, 2021 at 17:24

1 Answer 1


Yes, you have to meet current Code if it’s structural, and the 4x4’s are considered structural.

The spacing of your 4x4 support posts is not what is important. If the walking surface of your deck is more than 30” above the adjacent ground, then the Code (See ICC Section 1013.1) requires:

  1. Guards (deck railing) around the deck that is between 34” and 38” high. (This is for residential construction only.)

  2. The deck railing shall not allow a 4” sphere pass through it.

  3. The deck railing shall withstand a 200 lb. force applied at the top of the guard (deck railing). (I’m going from memory on this one. I can’t find it in the Code.)

The 6’ spacing might have been referenced because it works out to an even module around the deck, but it’s not required.

Also, if you live in a seismically active area or high wind area you must anchor each end of your deck to your house foundation. I’d use something like this:


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    Check with your local AHJ... if the deck is high off the ground, you might need 42" high railings. Commented Nov 3, 2021 at 3:41

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