I hope to build a retaining wall 5' and 6' tall by 44' long.
I had hoped to build it with a concrete footer, "cinder" blocks (filled with concrete) and slate veneer - but I am wondering how big & deep the footer should be to avoid future problems. We live in Atlanta so the frost depth is about an inch.
An alternative is to use concrete blocks from a home improvement store - but I don't really like the look, and they are only intended for walls up to 3'-4'.
There is an existing retaining wall, actually part of the foundation which extends out about 6'. I would like to "extend" this wall with a 90 degree out-side turn, then 22' of 5' tall wall, then a 90 degree in-side turn, 5' of 6' tall wall, and finally a 90 degree out-sidet turn, and 17' of 6' tall wall.
That footing doesn't sound large enough. Not so much the depth, but the width. You need to account for the lateral loads of the earth pushing on the wall and that all translates into the footing system. On the link below you'll find an image of the typical sections through a retaining wall. You will need to replicate, to a certain degree, the one in the top right. Might be worth touching base with an engineer to ensure that the wall you build will outlast your desire to do it over again.