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The Antioch Patio Spec, Line by Line

Four numbers govern a residential patio slab here, and each one exists because somebody once got it wrong. What they are, what they are protecting against, and how to get them onto your quote.

Updated October 2026 · Antioch Concrete

Most of what a patio quote contains is negotiable: the size, the shape, the finish, when it happens. A short list of items is not, and those are the ones least likely to be discussed with you, because they are invisible in the finished job and they all sit below the surface you will actually look at.

The four that matter

Item	Specification
Slab depth	Four inches minimum, written as four and not three and a half
Beneath it	Four inches of compacted CA-6
The mix	Six bag
Entrained air	Three to six percent

Take them one at a time, because each is guarding against a specific failure.

Four inches, and why the wording is deliberate

The interesting part of this requirement is not the number, it is that somebody bothered to write it as four rather than three and a half.

Dimensional timber is not the size printed on it. Build a form casually from material that is nominally four inches and the slab you get is slightly less than four inches, every time, on every job, without anybody intending it. Specifying four rather than three and a half closes that door on purpose, which tells you the clause was written by somebody who had watched it happen repeatedly.

It also gives you a clean question to ask a contractor: is that four inches of concrete, or four inches of form?

CA-6, the item that does the most work

Under the slab goes four inches of compacted CA-6. It is a graded crushed aggregate, meaning a deliberate mixture of stone sizes down to fine material, and the mixture is the whole point. The fines fill the voids between the larger pieces, so under compaction the material interlocks into something close to solid rather than remaining a loose layer of stone.

This is the part of a patio that decides whether it is still flat in fifteen years, and it is the part nobody can inspect once the concrete is on top. Two questions are worth asking: what material, and compacted in how many layers. Material placed in one thick lift does not reach density all the way down whatever depth is written on the quote.

Six-bag mix and the air in it

A six-bag mix describes the cement content per cubic yard. It is a lever a supplier can move without anybody noticing, so it belongs on the paperwork as a specification rather than as an assumption about what will turn up.

Entrained air is the one we would fight hardest for. Three to six percent, as a deliberate network of microscopic bubbles running through the concrete. When water inside the slab freezes and expands, those voids give it somewhere to go. Without them the expansion has to push the surface apart instead, and that is precisely the flaking and pitting that turns a five-year-old patio around here into an embarrassment.

It is invisible, it is cheap, and it is not optional on anything poured outdoors in this county.

The joints, which the spec does not set for you

One item is conspicuously absent from that list and it decides as much as any of them. Nothing in a slab specification tells the crew where to cut the joints, and joints are what determine where your patio cracks.

Concrete shrinks as it cures and relieves that shrinkage somewhere. A control joint is a deliberate weak line that gives it a place to do so, below the surface and along something somebody chose. Cut too few, or cut them too late, and the slab picks its own line across the middle of the open area.

So it is worth asking two questions that no ordinance asks for you: where will the joints go, and when will they be cut. The layout should relate to the shape of the patio, picking up corners and any point where the slab narrows, rather than being a grid imposed on it. And the timing matters because a joint cut too late is a joint the concrete has already worked around.

Getting all four onto the paperwork

None of these numbers is exotic and none of them is expensive. What makes them worth writing down is that every one describes something you will never be able to check again after the pour day, and three of the four are below the surface entirely.

So ask for the specification as lines on the quote rather than as reassurance in the garden. Depth of concrete, depth and type of base, how many layers it is compacted in, cement content, air entrainment. A contractor who works to this will write it without hesitation, because it costs them nothing to commit to what they were going to do anyway.

There is a second reason to insist here rather than elsewhere in the county, and it is specific to this village. It has nothing to do with the slab and everything to do with who is standing on it, and we have set it out separately in nobody vets your contractor in Antioch.

What a patio costs against those specifications is in our patio pricing guide, and the finishes that sit on top of the slab are covered in exposed aggregate or a broom finish. To have it quoted, start at concrete patio.