The edging tool is a separate step from the finish
Once the concrete is screeded to grade and floated, a hand edger gets run along the inside of the form, top and bottom, before the forms come off. That is where the edge shape gets set, and it happens on the same trip as jointing, before curing starts.
It has nothing to do with whether the surface itself is broom, stamped, or exposed aggregate. Edge shape and surface texture are two separate decisions, and any finish can pair with either edge.
Radius edge, the default outside
A radius edge is a slight curve instead of a hard ninety degree corner. Outdoors that curve matters more than it looks like it should. A steel shovel edge or a plow blade set to scrape catches a sharp corner and chips it, especially once freeze and thaw have already worked the concrete near the surface. A rounded edge lets the tool slide past instead of biting in.
Step nosings get the same treatment for the same reason. A rounded nosing that stands up to a snow shovel is standard on the steps and stoops we pour, and it holds up better under years of winter than a sharp edge does.
Square edge, and where it actually earns its keep
A square edge is the sharper, un-radiused version, and it is not wrong, it just fits fewer situations. Indoor slabs, like the interior of a shop or garage floor, do not see a plow blade or road salt, so there is nothing for a square edge to lose to.
It also shows up where the slab has to key against something rigid, a paver border, a metal edging strip, or a phased pour where a later section will tie into a clean, formed line. On a job like that, a crisp edge is what the next piece of work needs, not a liability.
- Interior floors with no weather exposure
- A slab that keys against a paver or metal edge
- A staged pour where a later section ties in against a formed line
What we default to, and why we would talk you out of the other one
If nothing about your job calls for a square edge, we cut a radius edge and do not charge you extra for it. It is standard finishing labor either way, part of the same crew, same trip, same price band as the rest of the pour.
If you specifically want a square, architectural edge on an outdoor slab that sees plows and salt, we will pour it that way if you ask, but we will tell you honestly that a radius edge is going to hold up better over time on that particular surface.
Edges at corners and where a slab meets a fixed object
The edger also has to work around whatever the slab meets. Where a patio meets a house wall, a stoop, or a post footing, that joint is isolated with a compressible material so the two surfaces can move independently, and the edger still rounds the exposed side of the concrete the same way it would on an open edge.
Inside corners take more hand work than a straight run, since the tool has to be turned through the angle without dragging or flattening the radius. A crew that rushes that step leaves a corner that chips first, usually within the first winter.