You’ve probably heard it before, but it doesn’t make the pill and easier to swallow. Cracks (hairline) are a normal part of a concrete installation. There are lots of reasons for this but most are related to the shifting ground underneath your concrete. The good news is that this type of crack (no wider than the width of a nickel) poses no threat to the structural integrity of the installation. Regardless of whether it’s cosmetic or not, it can be annoying, and so we want to spend some time addressing the issue further.
What’s the cause?
As mentioned above, most hairline cracks are completely normal and there’s no need for worry. Due to the concrete’s make-up, it can naturally crack a little as it dries. When under external stressors and weight, cracking over time is to be expected, but not excessive cracking. A nice rule of thumb: if you can drop a nickel in the crack, then it’s worth a call to a professional (like JLC Martinez Concrete!) who will either begin remedial work or provide advice on how to address the issue.
What else is contributing to the cracking?
- Expansion- Concrete will expand in volume as it heats up, which we see a lot of in the Central Valley. When concrete expands and pushes up against something that will not give, then that strain can cause some cracking.
- State of the soil- If the earth under the concrete becomes soft or saturated, the sheer weight of the concrete slab can cause that soil to compress or “settle.” If this process takes place and results in an uneven settlement, then cracking can result.
- Poorly placed joints- As the earth beneath the concrete shifts, this places stressors on the concrete. If joints are not cut into the concrete in the appropriate places, then it will crack.