Concrete gives up water as it cures and shrinks slightly while it does. A slab is a large, flat, restrained panel of a material that is strong in compression and weak in tension, so when it shrinks, something has to give. It cracks. That is not a defect, and no contractor can honestly promise otherwise. Anyone who tells you their concrete will not crack is either new to the trade or selling you something. The promise worth having is a different one: that the cracking happens where it was planned to happen, in a line you can live with.
That is why the conversation about cracks belongs before the pour rather than after it. Joint layout, reinforcement, base preparation, and slope all influence where a slab relieves stress and how much movement it can absorb without opening up. A homeowner who understands that going in asks better questions and gets better work out of the bid process. A homeowner expecting a crack-free slab is guaranteed to end up disappointed by an otherwise perfectly good driveway.
A control joint is a deliberate weak line. It is cut or tooled into the slab so the concrete has an easier place to crack than the open field, and the crack that forms runs down inside the groove where you never see it. Spacing and layout are worked out by your contractor for the shape of the pour, the reinforcement, and how the slab will be used. The joints have to go in while the concrete is still at the right stage, which is another reason pour day is not the moment to be making decisions.
On decorative work, the joints usually do double duty as part of the pattern, which is why a well-laid-out patio looks intentional and a poorly laid-out one looks like somebody cut lines wherever there was room. When joints are spaced badly or go in too late, the slab relieves itself somewhere else first, and that is where your random crack comes from. Ask to see the joint layout before the pour, not after you are looking at the result.
Fine cracks that follow the joints, or thin lines that stay closed and tight, are ordinary. Concrete moves with temperature and moisture, and thin shrinkage cracking is part of owning a slab. Those are cosmetic in most cases, and the sensible response is to keep water out of them rather than to tear anything out. Sealing joints and cracks is a maintenance chore, not an emergency, and doing it before winter is a good habit in this climate.
The cracks that mean something are the ones with width, displacement, or momentum. If one side of a crack sits higher than the other, the slab is not just shrinking, it is moving, and something under it moved first. If the crack widens noticeably from one season to the next, it is active. If you can trace it clean across several panels or through a joint that should have caught it, that is worth having somebody look at rather than filling and forgetting.
A slab reports on the ground under it. Cracks that step, panels that rock underfoot, corners that have dropped, and sections that have lifted are all telling you the same story: the support underneath is not uniform anymore, or it never was. Uncompacted fill, a trench that was backfilled loose, organic material left in place, or frost working on saturated ground will all move a slab. Replacing the concrete without correcting the ground buys you a nice-looking version of the same failure.
This is also where it is worth being clear about scope. Flatwork sits on the dirt. A house foundation is a different structure with a different specialty, and a foundation that is settling, bowing, or cracking is not a flatwork conversation. If that is what you are seeing, we would point you toward the people who handle it rather than pour a new slab next to the problem and call it solved.
Follow the water before you blame the concrete. A downspout emptying next to a walk, an irrigation head spraying the edge of a driveway, a low spot that ponds after every storm, or grade that sends runoff back toward the house will all soften and wash the material under the slab. Wet, unsupported ground compresses under load, and the slab breaks over the void. That failure looks like a concrete problem and is really a plumbing, grading, or landscaping problem wearing a concrete costume.
Water works on the top of the slab too. Anywhere water stands, it gets into the surface and freezes, and Utah gives it a lot of chances to do that between fall and spring. Cracks and joints are the doorway, which is why surface damage so often starts along them and spreads outward as flaking and pitting. Keeping the slab draining and keeping the joints sealed does more for the life of your concrete than almost anything else you can do.
Tight cracks in a slab that is otherwise flat and stable can be cleaned and sealed. That does not make them disappear, but it keeps water out of the crack and out of the base, which is the point. The same goes for resealing control joints. This is inexpensive maintenance on a slab you want to keep, and it is worth doing before winter rather than during the first thaw when the damage is already underway.
Replacement earns its keep when the slab is moving, when it holds water, when it is cracked through in multiple directions, or when the surface has failed broadly. Tearing out is what gives someone access to the base and the drainage, which is where the actual fix lives. Resurfacing is a real option for a sound slab with a worn surface, but it is a different project with a different lifespan, and it does nothing about ground that is still moving underneath.
Cleaning out and sealing a tight, stable crack is reasonable homeowner maintenance and it keeps water from getting under the slab. What it will not do is stop movement. If the crack has a lip, keeps widening, or the slab rocks when you step on it, filling it just hides the evidence. Have somebody look at what is under it before you spend a weekend on the surface.
Shrinkage cracking is tied to curing, so it typically shows up early rather than years later, and it is one reason joints get cut when they do. A fine crack appearing in the first season on a slab that is otherwise flat and draining is normal behavior. A crack that appears alongside a corner dropping or a panel rocking is a different conversation entirely.
Not by themselves. Every slab cracks, and a crack that runs inside a control joint means the joint layout worked. What can point at workmanship is cracking that ignores the joints, a slab that ponds water because it was never given fall, or a slab that broke because nobody prepared the base. Look at where the crack is and what it is doing, not at whether one exists.
Send it over and we will match you with a Wasatch Front concrete contractor who covers your area.