The standard call for a footing
Footings, or footers if that is the word you grew up with, under a house, a garage, an addition or a pole building commonly get a 4,000 PSI air-entrained mix here, the same standard we build to across our exterior work for Virginia freeze-thaw. It is a proven number for ordinary residential and light commercial footings, and it is where we start on most jobs before anything else about the site changes it.
When the plan overrides the standard
An engineered footing is a different situation. When a structural engineer stamps a plan with a specific strength, that number is the one that governs, full stop, whether it matches our usual call or not. We would rather read the plan and order to it exactly than default to a standard number that was never meant to apply there.
That is not a decision we make. It belongs to the engineer who sized the footing for the load it is actually carrying, and our job is putting their number on the concrete order correctly.
Every load above it comes down to this
Everything above a footing, the walls, the floors, the roof, comes down through the framing and lands on that narrow strip of concrete. A footing that comes up short on strength is not a cosmetic problem the way a crack in a patio might be. Our page on foundations and footers goes through what a footing does and why the ground under it matters just as much as the concrete itself.
Steel is a separate decision from strength
Reinforcement and PSI are two different questions that get answered together but are not the same choice. Steel run continuous through a footing, tied rebar in a grid, is standard practice on our foundation work regardless of which strength gets ordered, because concrete is strong in compression and weak in tension, and a footing bridging a soft spot needs the steel to hold it together.
What goes on the order before the footing gets poured
The strength spec, whether it is our standard or an engineer's number, goes on the ticket along with whether the load is being placed with our line pump. Footings are the work most likely to need it, since a loaded ready-mix truck has no business backing up to an open trench. Both the strength and the pump spec belong on the same order, decided before the first truck is loaded.
Strength is not the only variable that matters
PSI answers one question about a footing. It says nothing about what the footing is sitting on, and a strong mix poured over soft, loose or freshly disturbed ground can still move. Our own layout and inspection process on foundation work covers that ground condition separately from the strength spec, because the two problems do not fix each other.
Whether your particular job needs a permit and a footing inspection before concrete goes in is its own local question, and one worth a phone call rather than a guess. Our Virginia permit guide walks through that side of it.