There is an old line in the trade: there are two kinds of concrete, concrete that has cracked and concrete that will. It is a little glib, but the core truth holds. Concrete is strong in compression and relatively weak in tension, and it shrinks as it cures and dries. Some cracking is a normal part of how the material behaves.
What matters is why a crack formed, whether it is still moving, and whether it is letting water reach the soil below. In the Albuquerque metro, our soils and climate add a few causes you will not read about in guides written for humid regions.
Shrinkage cracking
Plastic shrinkage
These form in the first hours after placement, when the surface loses water faster than the concrete can bleed it up. Low humidity, wind, and sun make this a real risk here. Plastic shrinkage cracks are usually short, shallow, and sometimes roughly parallel. They are often cosmetic, though they can give water and debris a path into the surface. Our guide to how concrete cures in a dry climate covers how evaporation control and prompt curing help prevent them.
Drying shrinkage
Over weeks and months, concrete shrinks slightly as excess water leaves. If the slab is restrained by the ground beneath it, by footings, or by adjacent structures, that shrinkage builds tension until the slab cracks somewhere. This is why control joints exist.
Control joints: planning where cracks go
Control joints are intentional weak lines, tooled or sawcut into the slab, that encourage shrinkage cracks to form in a straight, tidy line instead of wandering randomly. A common rule of thumb is to space joints, in feet, roughly two to three times the slab thickness in inches, so a four-inch slab often has joints somewhere in the eight-to-twelve-foot range. Panels are also typically kept close to square, and joints are placed at inside corners and changes in shape.
If you see a crack running diagonally from the corner of a garage or step, or a crack in the middle of a long, narrow panel, missing or poorly placed joints are often part of the story. Timing matters too: sawcut joints made too late may not prevent random cracking.
Soil movement: the high-desert factor
In much of the metro, the most consequential cracks come from the ground moving, not from the concrete itself. Our in-depth guide to what is under your slab covers each soil type, but here is how they show up as cracks.
Settlement from collapsible soils
Some dry sands and silts in the area are low-density and can compact suddenly when wetted. The classic trigger is water: a downspout that dumps beside a slab, a drip line along a patio edge, a broken sprinkler, or monsoon runoff with nowhere to go. The result is often a slab section that drops, tilts, or cracks with one side lower than the other. These cracks tend to show vertical offset, and they often continue to move if the water source is not fixed.
Heave from expansive clay
Clay-rich pockets swell when wet and shrink when dry. A slab over expansive clay can lift in one area and drop in another as moisture changes, producing cracks, raised edges, and doors or joints that bind. Uneven moisture, such as irrigation on one side of a slab only, makes it worse.
Thermal movement
Albuquerque often sees day-night temperature swings of 25 to 35 degrees, plus intense direct sun. Concrete expands and contracts with temperature, and slabs that are tightly restrained against walls, curbs, or other slabs can crack or spall at edges. Isolation joints, a compressible material between the slab and fixed objects like foundations or columns, help accommodate that movement. Freeze-thaw cycles in winter add another stress, especially for non-air-entrained exterior concrete.
Overloading
A slab designed for passenger cars may crack under a loaded dump truck, a concrete truck, a moving van, or outrigger pads from a lift. In commercial settings, concrete parking lots often crack first along drive lanes, dumpster pads, and delivery areas where loads concentrate. Edges are especially vulnerable because there is less slab to spread the load.
Cosmetic or structural?
Not every crack needs action. Here is a general way to think about what you are seeing, with the caveat that anything near a foundation or structural element deserves a professional look.
- Usually cosmetic: hairline cracks with no offset, cracks that follow control joints, fine surface crazing, and cracks that have not changed over several seasons.
- Worth monitoring: cracks that are widening, cracks that let water in near a foundation, and cracks that are slowly developing a lip.
- Likely more serious: vertical offset that creates a trip hazard, cracks accompanied by sticking doors or wall cracks inside the house, slabs that rock or sound hollow, and cracks in foundation walls or footings.
Repair, level, or replace?
The right fix depends on the cause. Sealing a crack that is caused by an active water source, without fixing the water source, rarely holds up.
- Concrete repair fits stable cracks, spalled edges, and surface damage, using routing and sealing, patching, or resurfacing where the slab itself is sound.
- Concrete leveling fits slabs that have settled as a unit but are otherwise intact, lifting them back toward grade and filling voids underneath.
- Replacement fits slabs that are badly broken, heaved, or settled in multiple directions, or where the base and soil need to be corrected before new concrete goes down.
Whichever path you take, the long-term answer usually includes the boring parts: redirecting downspouts, pulling irrigation away from slab edges, sealing joints, and keeping up with routine maintenance. If you have a crack you are unsure about, you can ask us to take a look and we will tell you plainly whether it needs attention.