Concrete cracks: repair, or replace?

Concrete shrinks as it cures, so it cracks. That is not a defect, it is the material. Control joints are cut at set spacing to decide where those cracks go, which is why a clean line running along a joint is the system working rather than failing.

What matters is which cracks you have.

These are surface problems, and the slab underneath is still doing its job:

• Hairline and medium cracks that have not moved out of plane
• Spalling and flaking on the top surface
• Blown-out edges and corners
• A slab that has settled evenly and can be lifted back to level

Cracks get cleaned out and filled with a flexible sealant, patches get a bonding agent so new concrete sticks to old, and a sunken slab can often be raised for a fraction of a replacement. Resurfacing covers the rest.

Break it out and start again when:

• The two sides of a crack sit at different heights, which means the ground under one side has moved
• The slab is heaved, rocking or broken into pieces
• Cracking runs in a map pattern across the whole surface
• The base under it has washed out or failed

Patching a slab whose base has gone is money spent twice. The patch cracks again in the same place, usually within a season.

We come out and look before quoting anything, and we will tell you plainly which of the two you have. If it can be fixed, we fix it — concrete repair is most of what we do in winter. If it is past that, we say so rather than selling you a patch that will not hold.