Every concrete slab cracks eventually — it's in the nature of the material. The question isn't whether your concrete has cracks; it's which cracks are cosmetic, which are warning signs, and which are already letting water destroy your slab from below. Here's how to read them.
Hairline Cracks (Under 1/8 Inch): Usually Cosmetic
Thin surface cracks with no height difference between the two sides are usually shrinkage cracks from the original cure, and they're rarely structural. In most climates you could ignore them. In Colorado, we recommend sealing them anyway — because our freeze-thaw cycles turn today's harmless hairline into next spring's quarter-inch gap. Water gets in, freezes, expands 9%, and pries the crack wider every single cycle.
Wide Cracks (1/8 to 1/2 Inch): Seal Them Now
Cracks this size are actively admitting water to the soil beneath your slab. That water erodes the base, which leads to settlement, which leads to more cracking — the failure cycle that ends in slab replacement. Professional flexible sealant stops the cycle. This is the highest-value maintenance dollar you can spend on concrete: a few hundred dollars of sealing routinely prevents thousands in lifting or replacement.
Offset Cracks: The Serious One
If one side of a crack sits higher than the other, the soil under your slab has already failed and the pieces are moving independently. This is beyond sealant — the slab needs to be lifted and stabilized with foam first, then sealed. Offset cracks are also trip hazards, which matters for liability on walkways.
Why DIY Crack Fillers Keep Failing
The gray caulk tubes from the hardware store are rigid when cured. Colorado concrete moves constantly — expanding in 95-degree summers, contracting at 10 below. A rigid filler breaks its bond within a season or two and pops out. Professional-grade sealants are engineered to stretch and compress with that movement, and we pair them with backer rod so the sealant cures in the right shape to flex for years.
There's also the joint question: your slab's control joints (the straight grooves) and expansion joints need the same flexible sealing as random cracks, and they're usually in worse shape. We treat both in the same visit.