Is there a maximum allowable height for a 4×4 deck support post?
A Glenn Mathewson, a building inspector from Westminster, Colo., responds: Unfortunately, there are few pre-engineered and universally accepted standards that address this question. The International Building Code and the International Residential Code (IRC), the foundations for most of the building codes in the United States, specify only that a post must be at least a 4×4. This isn’t meant to imply that 4×4 posts are good for all conditions, merely that there’s no condition where less than a 4×4 is acceptable. For most decks, post size is overlooked unless an inspector notices the unusual height of a particular deck. A short 4×4 can carry an awfully big load, and many deck builders use 6×6 posts as a standard, regardless of the height or load of the deck. Though the height of a deck is often questioned only in regard to the requirement for guards, it is a factor in determining the height or “span” of the posts. When an undersized post is compressed along its axis by the weight of the
