Concrete – Connect new footings to old footings

You definitely want your footings to extend below the frost line, otherwise as the ground freezes below your footing it will swell (as water does when it freezes) and the force of the swelling WILL push your footings out of position.

Ice breaks mountains - a porch doesn't stand a chance. :) Dig DEEP. With a frost line going as low as 4', I'd dig down 5.

However, that said, the FOOTING doesn't need to be 22" wide from 5' down all the way to the surface - a 22" by roughtly 12" deep footing put 5 feet down and a 6" or so wide reinforced wall coming up to surface would avoid the problems of freezing and save on concrete while offering structure.

This kind of work usually requires a permit as well, and its hard to conceal, so you might want a structural engineer to draw up proper approve-able plans.

Can I convince you to not do this ?

Honestly not trying to be an ass.

Please, please - Get a quote from a company that builds retaining walls.

The quote will cost very little or nothing.

You will be shocked at the cost, and not in a good way.

The quantity of material needed to build the wall, will amaze you.

Please get a quote or two first.

I promise you, you will not regret it.

Block walls work in compression, heavy things directly on top of them is fine.

Side to side, their goal in life is to tip over, and they are damn good at it.

Blocks work because they are tied to very solid, heavy things at the top and bottom that run the length of the wall, and have regular supports at a right angle to the length of the brick.

A 1' deep pile of soil, behind a 4' block wall, 1 block long, weighs 500 pounds.

The path of least resistance is to knock over the wall.

Blocks, attached with mortar, to the soil behind the wall about as strong as a 2x10 resting on its edge.

The question is more one of how many yards of concrete will you need to build the footing.