You've had someone out to look at the driveway, or you're about to, and you can already guess how it goes. One person says it can be patched, the next says there's no repair for that, only replace, and the two prices are so far apart they don't sound like the same slab. You don't want to pay for a fix that turns out to be money wasted, and you don't want to tear out concrete that had ten good years left in it.
The good news is that this is less of a judgment call than it sounds. A few things settle it, you can check most of them yourself in an afternoon, and a lot of the time the answer sits between the two, which is to replace the part that failed and keep the rest.
The short answer, before anyone gives you a number
Do we have to replace all the concrete to repair this driveway or can we just do the uneven/broken panels?
Usually you can do just the panels. Concrete is poured in sections divided by joints and damage tends to stop at a joint, so the panels that have sunk or broken can be cut out and replaced on a corrected base while the sound ones stay. Replacing everything makes sense when most of the panels have moved, when water drains toward the house, or when the repairs together would cost about half of a new slab.
Start with whether the slab has moved
This is the check that decides most of it, because concrete that's still sitting where it was poured can be repaired almost regardless of how it looks. Concrete that has moved can't be fixed from the top.
Lay a straight board or a long level across each crack and each joint. If both sides touch the board, the slab is flat and what you're looking at is the surface. If one side sits higher, or a panel rocks when you drive onto it, or a section has tilted away from the garage and left a lip, then the ground underneath has changed. Much of the Denver metro sits on clay that swells when it's wet and shrinks when it dries, heaviest through Highlands Ranch, Aurora and Littleton, and a slab on a thin base rides that movement every year.
That's the worry behind most of the hesitation we hear, put by one homeowner as "I'm worried my cracked driveway will continue to shift and it will crack all over again." For a slab that has moved, that's exactly what happens. Anything bonded to the top of it, whether that's a tube of filler or a whole overlay, cracks in the same place because the cause is still underneath. A moved panel gets fixed by taking it out and rebuilding the base under it, and that's concrete repair on the scale of one panel, with the rest of the driveway left alone.
When the damage is only on the surface
A slab that passes the board test and still looks terrible is the best case, even though it rarely feels like it. The usual description is a driveway that's "good in most places" with the surface worn down to the stone in others. In Denver that's nearly always a hundred freeze-thaw cycles a year and road deicer working on an unsealed surface, and it's shallow. The concrete under it is usually as strong as the day it went in. There are a few kinds of surface failure and they don't all get the same fix, so it's worth two minutes to work out why the top layer is coming off before you price anything.
Small areas can be patched. When the wear is spread across the whole slab, resurfacing puts a new surface over the old concrete and gives you one even color, and it holds as long as the slab is flat and the cracks have stopped moving. Narrow cracks with both sides level are a job you can often do yourself, and which product survives a winter here is covered in filling concrete cracks with a tube from the hardware store.
People ask what the drawbacks of just repairing it are. The first is that a patch shows, because new material never matches thirty-year-old concrete. The other is that a repaired surface is still an old surface, so it needs sealing afterward and again every two to three years or the same weather starts in on it.
How much of it has failed, and where
Walk the slab and count panels. One or two that have sunk or broken up in a driveway that's otherwise flat is a panel replacement. They get cut out at the joint, the base gets dug out and compacted properly, and new concrete goes back in that one spot. It happens most at the street end, for reasons we went through in why only the first ten feet of a driveway falls apart.
The usual objection is the look. One homeowner wanted the whole thing replaced because half old and half new "won't be uniform in color," and that part is true. New concrete doesn't match on day one, though it weathers toward the old color over a few seasons. If a two-tone driveway is going to bother you every time you pull in, that's a fair reason to do more. Just know you'd be paying for the look at that point, since the old panels were fine, and anyone pricing it should tell you so.
Replacing the whole slab is the right call in a few situations. Sometimes most of the panels have moved and there's little sound concrete left to keep, or the slab has broken into so many small pieces that there are no panels to save. Sometimes the problem is where the water goes. No repair changes the slope a slab was poured at, and one that sends water toward the house or the garage will keep doing it. And now and then the first panel comes out and shows thin concrete sitting on dirt with no base, which usually means the rest was built the same way. That's removal and replacement, and the point of doing it is the base and the drainage as much as the new concrete.
The rule of thumb on cost, and the one question to ask
The rule of thumb in the trade is that once the repairs add up to around half the cost of replacing, you replace. Past that point you're putting serious money into a slab that still has its old base and its old problems. Below it, repair is usually the better use of the money. Age on its own doesn't decide anything, since a thirty-year-old driveway that's still flat is doing fine.
If you want to know enough to call BS on a quote, ask whoever is pricing it one thing: what caused this, and does your price fix the cause? A replacement quote should say what changes under the new slab, the base and where the water goes, because new concrete on the same ground does the same thing in a few years. A repair quote should say why it will hold. Lifting a sunken slab is a good example. It can level a panel that's still in one piece, but it doesn't change the soil that let it drop, which is how people end up saying it worked at first and sank again years later. When the ground under a panel has failed, we replace that panel on a compacted base.
If the answer is replace and it's already October
Pour season on the Front Range runs roughly April through October. A late pour is possible, but it means blankets, a changed mix and a longer schedule, and sometimes the honest answer is to wait for spring.
A slab that's failing but usable can almost always get through one more winter. Fill the open cracks that are level, so less water gets in to freeze. Turn downspouts so they don't empty onto the concrete. Where one edge stands a little proud and catches a toe, a small offset can sometimes be ground down to take the trip hazard away until the real work happens. Then get the measuring and pricing done over the winter so you're on the schedule when the weather turns.
Getting a straight answer on yours
Lay a board across the worst crack, take a photo of it and one of the whole slab from the street, and call us at (720) 782-8086. We'll come out, measure, check whether the damage is in the surface or under it, and find the cause. You get a written, itemized price with a plain answer on repairing it or replacing it, and we'll tell you when it's the smaller job.