Deep Pier Questions need quick answer

[Spyke]

Here is the deal. I an doing a small porch on the front of my little house in Illinois. The plan is to build it on 8" piers and tie it into the house to provide additional support for the existing house post and pier foundation as well as the new porch. I will be digging at least 42" to be below frost line.

Here is my $64K question.

If I rent a power auger to dig the holes, will I need to use tubes below ground? I know the point of the tubes is to keep the walls of the pier smooth so that the frost heave doesn't push it up, but the holes dug with the auger have nice smooth walls at this time of year because the ground is moist. I am thinking of using cut down tubes only where the pier top sticks out of the ground 6 or 8". My other thought was that this would also avoid having to backfill aound the tubes .

Hope this makes sense. Lemme know what ya think! Wanna be sure I do this right.

[John Raabe]

Your plan should work. You won't have a real footing at the bottom of the hole, but with decent soil and the light weight of the porch the bearing at the bottom of the pier is likely plenty.