Live with it, resurface it, or take it out
Not every ugly slab needs replacing. Concrete is supposed to crack a little. Hairline cracks that follow a joint line, or that you can barely catch a fingernail in, are shrinkage doing what shrinkage does. If both sides are still level, that is a cosmetic problem, and we will tell you so.
The line we look for is movement. Once one side of a crack sits higher than the other, a corner has dropped, a panel rocks under your foot, or a slab has heaved at a joint and catches a plow blade, the concrete is no longer sitting on solid ground. Patching a slab that is moving underneath buys you a season, maybe two.
Surface failure is its own category. Spalling is the top layer flaking and popping off, usually from de-icing salt, a poor finish, or water freezing in the surface over several winters. Shallow spalling on a sound slab can sometimes be resurfaced. Once you are looking at the stone in the mix, resurfacing is a paint job over a failure.
- One side of a crack sits higher than the other, or a corner has settled below the rest
- A panel rocks or tips when you step on the edge of it
- Wide cracks you can drop a pencil into, running the length of the slab
- Flaking deep enough to expose the aggregate or the reinforcement
- Water standing on the slab after every rain
Most of the time the base failed, not the concrete
When we get called out to a broken driveway, the concrete itself is usually fine. It broke because the ground under it moved. Red clay holds water, swells when it is wet, shrinks when it dries, and lifts when it freezes. Topsoil or soft fill left in the pad settles under load. Water off a downspout or a bad grade runs under the edge and washes the fines out, leaving a void.
Concrete takes enormous load pressed straight down on it and very little load asked to span. Set it on firm, free draining stone and it never has to span anything. Set it over a void and it turns into a bridge, and a four inch bridge with nothing holding the middle breaks.
So the diagnosis matters more than the demolition. We walk the site, look at where water comes from and where it goes, read the pattern of the cracking, and figure out what caused it. Same approach whether it is a driveway, a garage floor, a patio or a sidewalk.
Why pouring over the old slab repeats the failure
The question we get most often is whether we can just pour a new layer on top. Almost always the answer is no. A topping has nothing to do with why the old slab failed. The base is still soft, the void is still there, water is still running under the edge, and the new layer moves right along with the old one. Every crack underneath telegraphs through, usually inside the first winter.
Two practical problems come with it. Adding thickness raises the finished grade, so your garage threshold, your walk and your approach at the road are suddenly wrong by a couple of inches. And a topping only sticks as well as the surface under it, which on a spalling slab is not very well.
Resurfacing does have a place. A sound slab sitting flat on good ground, with a worn surface and grade to spare, can be a candidate, and we will say so when we see one. But if the base is the problem, the concrete has to come out.
Demolition, breaking and haul off
Removal is machine work. We break the slab into manageable pieces with a hydraulic breaker and work by hand around anything delicate. Old wire mesh and rebar have to be cut and pulled out with the pieces, which is slower than people expect and is a good part of why removal is priced separately from the pour.
Where the slab meets something that stays, a garage floor, a stoop, an apron at the road, we saw a straight line first. The break stops where we want it, and the joint between old and new ends up clean instead of ragged.
Then it all leaves. Broken concrete is heavy, and a driveway's worth of it is far more material than most people picture. We load it out and haul it off, and disposal is part of the number on your estimate.
What to expect on your property
Removal day is the loud day. It helps to know what it looks like before it shows up.
- Noise. A breaker on concrete carries. It is loud for the hours it takes and then it is over. If you work from home, tell us and we will talk about timing.
- Dust. Sawing and breaking make dust. We keep it down where we can and cut wet where that makes sense.
- Equipment on the ground. A machine, a truck or trailer for the material, and tracks across part of the yard. We show you the route before we start.
- Buried lines. Move vehicles, and tell us about septic lines, a drain field, a shallow water line or invisible fence wire.
- Time. On a typical residential slab, removal and haul off is its own day or two before a form board goes down.
Re-grading and compacting before the new pour
This step is the whole reason removal beats patching. With the old concrete gone, we can finally see and fix the ground that broke it. We strip out the soft stuff, the contaminated stone, the topsoil that worked its way in, the wet spot that never drained. Then we cut the grade back where it belongs and bring it up with crushed stone in lifts, compacting as it comes up instead of dumping it in one layer.
We set the slope while the ground is open. Water has to run away from the house, the garage and the shop, not toward them. Plenty of failed slabs were pitched the wrong way from the day they were poured.
Then the new work goes in the normal way. Forms set to shape and thickness, wire mesh or rebar tied and held up in the slab, ready mix placed and finished, and our own line pump run when a truck cannot get near the forms. There is more on that machine and how we use it on our pump page. Control joints get cut on the right spacing so shrinkage happens in a line we put there.
While it is open, fix what bothered you
Replacement is your one cheap chance to change things. The demolition and the base work are already in the price, so a change to the shape or the drainage costs only the extra concrete and a little form time.
- Width. Add a foot or two so doors open over concrete instead of mud, or widen where you swing a trailer around.
- A turnaround or a parking pad off the side, so nobody has to back the whole drive out to the road.
- Drainage. Re-pitch the surface and get downspouts discharging past the edge instead of alongside it.
- Thickness where it counts. If a dually, an RV or a loaded trailer parks in one spot, we thicken that area now rather than watch it break again.
- Reinforcement. If the old slab had nothing in it, a rebar grid tied and chaired into the new one runs $0.75 to $1.25 extra a square foot, and it is usually money well spent.
What tear out and replacement costs
Removal is its own line on the estimate, stacked on top of the new pour. Breaking the slab, cutting the old steel out of it, loading it and getting it off your property adds $2 to $3 a square foot. That is machine time, trucking and dump fees a fresh pour never has.
The pour underneath it is priced on whatever band fits what goes back in. A driveway at 4 inches runs $8 to $12 a square foot installed. Patios, garage floors, sidewalks, foundations and stamped work each carry a band of their own, and every one of them is published on our cost page, with real driveway sizes worked all the way through on the driveway cost page under it.
We measure, read the ground, and put the number on paper for you at no charge, along with the workmanship warranty, terms confirmed on the written estimate.