For a deck I'm assuming?

You can't in most locals. Depending on your area, frost level and deck loads come into play.

For example you may be able to place a pier block on a min. 3" slab I've heard, but most building dept. will want a proper footing and pier with rebar, then a min. 1" stand-off post base embedded. Even more will be required in coastal, high wind, earthquake zones, or high termite infestation or all of the above for us here in Cal.

Alter Eagle Construction & Design

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