How can I stop the porch from sinking? It sinks about an inch a year. I dug 42 inches down and filled it with cement for the porch 3 footings. The porch is 7 X 21 feet with a roof. I have to jack it up ever year to make it level again. Any ideas?

Ted, check the drainage around the porch. It sounds like the water run off from your house and precipitation is heading back towards the porch, thus continually soaking and softening the soil beneath your footings and making it possible for the porch's weight to force them down.