I have a porch on the back of my house that was not built by any code except maybe “had enough beer, let’s start that porch now.” It has a new layer of shingles on the roof and that’s the best thing that can be said about it. It looks like it was set on 4×4 pressure treated posts set on top of the ground. Since the ground slopes away from the house, some of the 4x4s are actually suspended above the ground at this point. What can I do to support this porch, other than getting rid of it completely and re-siding the house where it was?

You could brace the porch roof up, take out the old posts, pour new footings, and then put up new posts. If the posts are not to code though you might need to check other structural elements too.

I would get some precast concrete footings with 4×4 anchors cast in, and new pressure treated 4x4s. Remove one 4×4 and set a footing so about 2 inches protrudes above ground. Cut a 4×4 to fit, and install uncut end down. You should adjust the length of the 4x4s to properly slope the porch. Make it slope down from the house, about 1/4 to 1/2 inch per foot. Once that 4×4 is set, go to the next.

I assume you are saying that you have no floor under it. Perhaps putting a deck below for the posts to sit on. If you are not into such a project right now, just dig down a couple of feet below the posts and pour a concrete footing.

You’ll need to establish a value for the porch.The simple solution is to mount the existing posts, if they have not become infested, on precast piers immersed a couple of inches into the topsoil.Immersing them any further may make them and the porch subject to heaving, given your climate zone.