Concrete answers
Why does concrete crack?
The short answer
Concrete shrinks slightly as it cures and moves with temperature and the ground beneath it. Because it is strong in compression but weak in tension, that movement causes cracks. Control joints, reinforcement and a solid base keep cracks small and in planned places.
Common causes
- Shrinkage as the concrete cures and dries.
- Ground movement, especially clay soils that swell and shrink.
- Water washing out soil under the slab.
- Loads heavier than the slab was built for.
- Missing or shallow joints, so the slab cracks where it wants to.
- Tree roots lifting the slab.
Normal vs. a problem
Hairline cracks, especially in or near control joints, are common and usually cosmetic. Cracks that widen, have one side higher than the other, or let water under the slab are worth having looked at.
Preventing cracks in new concrete
A compacted base, reinforcement, the right thickness, good drainage, joints at the right spacing and proper curing all reduce cracking. How control joints work.
This page is general information. Every slab and every yard is different, so the right answer for your concrete comes from looking at it in person.
Ready to talk about your concrete?
Let's get your project on solid ground.
Tell us what you need and we'll get back to you to talk it through and set up a time to look at the job.
Prefer to call?(903) 555-0100