It depends … some cracks are more concerning than others …

Control joints are purposefully set into a concrete slab when it is first poured to provide a place for cracks to go when the slab moves in response to temperature changes and movement of the earth beneath it.  In other words, cracks are directed to the control joints so that they will crack in a straight line instead of randomly throughout the slab.  When cracks appear in the control joints, they can be filled with a sealant to prevent moisture intrusion.

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Cracks in concrete may be cause for concern depending on the type and location of the crack.  If the cracks are in control joints or are surface cracks, simply filling the crack with an appropriate filler will help prevent further damage.  If the crack goes all the way through the slab (structural crack), there is not much that can be done to prevent the eventual decay of the affected areas.

Hairline cracks, or surface cracks, are small fissures in the top layer of the concrete and should be repaired if they are widening with time, are a hazard, collect dirt or are unsightly.  While they may seem minor at first, left unattended these cracks will widen, worsen, and will allow water to penetrate the surface slab.  In the winter, water in the slab will expand and contract as it goes through freeze and thaw cycles, eventually resulting in concrete surface failure.

Hairline Crack in Concrete - Causes, Repair and Prevention - The Constructor

Repairing surface cracks is a simple fix and most homeowners can do it themselves with appropriate concrete repair material.  Being proactive in properly repairing surface cracks adds to the slab’s longevity and minimizes future expensive concrete fixes.

Structural cracks, wider than a credit card that run through the entire slab require repair and may even necessitate replacement of the concrete.  Structural cracks run vertically through the entire slab and repairs can be expensive.  A mesh with an overlay may disguise and possibly add time to the life of the slab, however, there is no complete or permanent structural “fix” currently available on the market.  As time goes on, each slab piece will move independently of each other, and parts of the slab may break into more pieces until the concrete surface is no longer level.  At this point, the solution is to completely tear out the affected areas and pour a new concrete slab.

Image result for images of structural cracks in concrete

At what width does a crack in concrete become a problem?  Unfortunately, there is no definite answer, and it can vary from one project to the next.  The answer may also change with the person’s perspective – what is acceptable to the contractor, engineer, or architect may not be acceptable to the owner who must live with the crack day after day.  Even the American Concrete Institute has no standards or recommendations that give a “yes” or “no” answer as to what cracks need repair based on width and other factors (

When installed properly, concrete is one of the most durable and long-lasting products in and around your home.  However, it is not maintenance free and it requires homeowners to be proactive at the first sign of cracking.  As a concrete contractor will tell you, “Yes, we guarantee our concrete … we guarantee that it will crack!”