Repair or replace a concrete footing
When an old footing has sunk or cracked and the deck or porch above has dropped with it, the question is whether the structure can be brought back up or the footing has to go. If the footing itself is sound and sits deep enough, foundation raising can lift what's above it. If it's shallow, undersized or sitting on loose fill, I'd rather replace it, because a new structure on an old mistake usually settles the same way.
What shapes the cost of concrete footings
Footing type comes first, because simple spread footings are usually the most economical and specialized pile footings usually cost the most, so it's the first thing to compare when quotes don't match. After that come the number of footings, how deep they go and whether wet ground slows the digging. Cutting back on depth to save money is the one trade I won't make, because the footing is the part that carries everything else.