Rotted deck posts

I am in Columbus, Ohio. I have a 3-foot tall deck that I am repairing it because it is 20 years old and has rot in various places.

The beam support posts are 4x4s embedded in concrete. The top of the concrete is about 4 inches below the surface, so part of the post is in direct contact with the soil and is rotting. I do not know how deep the footers go, but in central Ohio, the frost line is 32 inches.

I'd like to avoid digging new footers because the deck framing is still present and it is very hard to work in there. My preference would be to cut off the posts below the surface, then add concrete to extend the footer upward, then put new posts in with a metal spacer to keep the post dry.

But there is a potential problem with that plan: will my newly added concrete footer extension be a lip for frost heave to grab and push upward?

Are there any ideas for how to repair this foundation without digging 9 new footers at 32 inch depths?

 

Do as you explain. Cut the pt at footer level, drill 1/2" holes in the top of the old footer and install a few stubs of rebar that will stay below the level of your new height. Form it up and make a pour. Use post bases for your post installation. They have built in spacing.
You are assuming 32" depth, and I hope they are to code. But only one way to know for sure, right?

 

Will there be a problem if the footer diameters are different? Should I try to make the top one smaller to avoid a place where the frost could lift it? I've heard similar advice about not overflowing the tube to prevent a lip from forming.

I can dig up one of the outer posts to check the depth. If it's good, I'll assume they all were. If not, I'll redo them. But they've lasted 20 years... I'm mainly concerned about preventing rot.

 

I dug out about 18 inches of dirt around one of the posts I have. The post is actually in very good shape. It has nearly all of the material still left, after 20 years being in the ground.

I got nervous and checked because the post for our pergola rotted completely through. I guess the deck was built differently and has stood up to the elements. I can't exactly explain why -- different wood, perhaps?

I'm going to re-bury the deck post in the same soil and not worry about checking the other posts. Any potential issues with this?

 

How can you see the material (4x4 post) if it is embedded in concrete? Just curious.