Dek Block as base for poured pier?

[IHDiesel73L]

I'd be curious to hear what others think of using a Dek Block as the base for a poured pier?  Dek Blocks have an 11" x 11" base and an 8" x 8" top.  I am thinking of placing a Dek Block at the bottom of a 48" deep (required frost depth in these parts) hole on a 6" gravel base.  On top of the Dek Block, an 8" form tube would be placed with some kind of simple wood form to join the two and make sure that no concrete leaks out.  Concrete would then be poured, and the tube would be backfilled.  Using this method, a 8" x 48" pier would only require two 80lb bags-a big deal if you're out in the woods mixing by hand, or just trying to use resources efficiently. 

The only rub I see with this is sufficiently tying the column to the base.  One idea I had would be to drill a 1/2" hole through the center of the deck block and run a length of 1/2" rebar up through it that would run the length of the pier.  About 4-5"  of the end of the rebar would be bent into an "L" shape so that the long end would be threaded through the bottom of the Dek Block, but it wouldn't be able to be pulled all the way through by frost action. 

The 11 x 11 base yields 121 square inches of bearing area-more than a 12" diameter circular pier, which, if poured to 48" deep, would require slightly more than 5 80lb bags of concrete.  So again, let's say you need to pour 10 piers, that would mean a difference of 30 80lb bags-4000lbs of concrete, worth about $114.  The Dek Blocks cost less than $7 a piece at my local big box store.  Thoughts?

[Don_P]

You're well outside of code. A dek block is prohibited for a deck in most places. A pier is an engineered foundation for a dwelling as well. Rebar must have a minimum of 1.5" of concrete cover. This is a very small pier.

For a basic gravity check, what is the load on the most heavily loaded pier, what is the allowable soil bearing capacity. That determines the minimum footprint. Then the elephant in the room is how to handle lateral loads, there is the main reason for the engineer.