Holes and cracks in polished concrete: patch, fill, or leave
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Holes and cracks in polished concrete stay open unless we fill them. Polishing grinds and shines the slab you’ve got, and it lays no new coat on top to cover them. Your Slab Boss Polish quote has 2 groups for this, 1 for holes and cutouts and 1 for cracks, and both start at “leave it as is,” which costs nothing.
A hole is a gap somebody made on purpose. A crack is the slab shrinking or moving on its own, and some keep moving after we leave.
Where do holes in a concrete floor come from?
Most of them came from whoever used the building before you. We find nail holes where walls came down, anchor holes from shelving and machines, and cutouts where a pipe or drain used to come up. A nail hole can be the size of a pencil tip. A cutout can be a foot across.
Carpet installers nail tack strip into the slab, so pulling it up tears out nickel to quarter size holes along every wall. We can patch them, but they’ll still show under a polish. We say that up front, because some owners mind and some don’t.
Why holes stay open
A polish shines the slab you have. It does not add a layer on top, so nail holes, anchor holes, and cutouts stay open.
Leave holes as they are
Free and fast.
Pro: Nothing is added to your price.
Con: Holes stay open and show, dirt collects in them, and they can catch a heel.
Patch and grind flush
We fill each hole and grind it flat.
Pro: It is quick and low cost, and the floor is flat again.
Con: The patch color will not match. Plus materials.
Match-patch attempt
We pick rock and resin to blend each patch with the floor.
Pro: It is the best look we can get.
Con: It is an attempt, not a promise. Plus materials.
Leave holes as they are
They stay open, and you’ll see them. An open hole can catch a heel or a cart wheel, and it fills up with dirt and water. So a shop floor full of anchor holes may be worth patching even if nobody cares how it looks.
What does patch and grind flush do?
We pack each hole with patch mix and grind it flat with the floor, at $67 per hour as worked, plus materials. It’s quick and low cost. The hole disappears and the floor is flat again. The trade-off is color. Patch mix won’t match your slab, so every filled hole shows as a gray dot or a gray block.
What is a match-patch attempt?
We pick rock and resin to blend each patch into the floor around it, then grind and polish it with everything else. It runs $67 per hour, plus materials. It’s the best look we can get, and on a salt-and-pepper floor a good match-patch can be hard to spot from 6 feet away. But it’s an attempt, not a promise. It takes more crew time than a plain patch, and a big cutout is harder to blend than a nail hole.
Pinholes and tiny holes in the cement
Our first coarse cuts open pits and pinholes in the cement between the rocks. Grout and Cutback fills them: we spread grout into the pores, grind the extra back to the slab, and hand-cut the edges. Filled pores can’t hold dirt, so the floor comes out tight. It’s an add-on line on your quote, outside the standard total and not billed by the hour: $1.20 a square foot plus $1.63 a foot of edge.
By our estimate, our Chinquapin House polish in Collierville had about 2.3 million pits after the first cuts. Two grout coats later, a rake light held low found hardly any.
Does polished concrete crack?
It does when the slab does. Every slab gives up water as it cures and shrinks doing it. The saw cuts in a floor are there so it cracks along a straight line somebody planned. A polish doesn’t cause cracks or stop them. It shows them.
Every Slab Boss Polish already fills those joints, at $3.30 a foot, inside your quote total. What’s left are cracks that wander off the lines, and we check which kind each one is first, because the kind decides which fix will last.
- A hairline shrinkage crack is under 1/16 inch wide, with no step up or down between the two sides. These are normal, and they hold still.
- A crack with a step has one side higher than the other. That means the ground under the slab is settling or moving, and nothing on top can fix what’s going on under it. Fill it, and it can open right back up. If we see one, we’ll tell you.
Two kinds of cracks
Every slab shrinks as it cures, so hairline cracks are normal. If one side sits higher, the ground is moving, and nothing on top fixes that.
Leave cracks as they are
Free and fast.
Pro: Nothing is added to your price.
Con: Cracks stay open and show as dark lines.
Fill cracks with resin
We fill each crack with resin and grind it flush.
Pro: It is quick and low cost, and dirt cannot sink in.
Con: The fill line shows. Plus materials.
Match-patch the cracks
We blend rock and resin to hide each crack as much as we can.
Pro: The crack is much less visible.
Con: It is not invisible, and it is not a promise. A moving crack can open again. Plus materials.
Leave cracks as they are
They stay open and show as dark lines. On a hairline crack, though, many owners stop noticing it after the first week, and leaving it costs nothing.
What does a resin fill do?
We fill each crack with a polyurea resin and grind it flush, at $67 per hour, plus materials. It’s quick and low cost. Sealing the crack keeps dirt and spills from soaking in, and the edges are less likely to chip. You’ll still see it, though, since resin is one solid color and reads as a thin line across the floor.
Can a match-patch hide a crack?
Mostly. We blend rock and resin to hide each crack, then grind and polish it with the floor, at $67 per hour, plus materials. It shows a lot less than a plain resin line, and on a busy floor it can almost disappear into the rock. It still shows a little, and we can’t promise how much. A crack that keeps moving can open again and show through the blend.
These hours aren't in your total
Your quote total covers the standard polish. The patch, match-patch, and resin fill choices for holes and cracks are billed by the crew hour as worked, plus materials. Your quote lists what you picked and what you left.
Which choice fits your floor?
- A shop where looks don’t matter: patch the holes and resin-fill the cracks, the quickest and cheapest fixes.
- A showroom: match-patch what people will see, and add Grout and Cutback.
- Every mark has to go: a polish can’t do that. Only a solid-color coating like a pigmented epoxy floor covers them all.
Other defects on your quote
Low spots, soft spots, and cut depth are the other 3 groups. Each has its own page, linked from the polished concrete slab defects guide. Then go back to your quote and pick what you want done.
