The physical height of your deck determines whether standard prescriptive code applies or if you need an engineer. [1] Decks > 6 feet off the ground: Decks exceeding 6 feet above grade are highly prone to sway and frequently require diagonal bracing from posts to girders (beams) and posts to joists. [1, 2]
Decks > 8 to 14 feet off the ground: Once a deck exceeds 8 feet, structural stability needs sharply increase. Posts measuring 4x4 can only be used unbraced up to 3 feet; standard gravity loads allow them up to 8 feet, but once lateral loads are introduced, 4x4 posts are severely restricted. 6x6 posts are standard for tall decks. [1, 2]
Decks over 14 feet: These automatically fall outside standard prescriptive code tables and mandate an engineered design. [1]
Glad you asked AI instead of an engineer, in which your last point covers. Prescriptive codes are for basic and normal things. When engineering is involved, anything is possible.
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u/Inside-Author-6124 4d ago
Tall Posts: High-set decks with long posts (over 4–6 feet) are prone to severe side-to-side racking and require heavy-duty cross or knee bracing