Garage floors carry more than people think — vehicles, tool chests, jacks, and sometimes a lift. Here's how thickness actually gets decided.
The baseline
Four inches is the common residential spec and it's adequate for daily drivers on a properly compacted base. But 'properly compacted' is doing all the work in that sentence: garage slabs sit on backfill placed inside the foundation walls, and if that fill went in loose, the slab thickness barely matters — it'll settle and crack at any thickness.
We compact garage fill in lifts before pouring. It's most of the reason our floors stay quiet.
When to pour more
Go thicker — five inches or beyond — when the floor will see: a vehicle lift (post loads are concentrated and serious), a heavy truck or loaded trailer parked long-term, machine tools, or a shop crane. Thickened areas can be local, too: we can pour extra section right where lift posts land instead of thickening the whole floor.
This is a cheap decision before the pour and an expensive one after, so bring your plans — even vague ones — to the estimate.
Thickness isn't the whole spec
A garage floor spec also includes rebar (in every one of ours), pitch toward the door so snowmelt drains, saw-cut joints on schedule, and a cure period before it takes traffic. Miss those and a thick slab still disappoints.
Jerry sizes all of it to how you'll actually use the garage — that conversation is what the free on-site estimate is for.
Related service
Garage FloorsA flat, crack-controlled slab that drains right and carries what you park on it.