Some things that worry people about new concrete are normal, and some are real defects. This page goes through them one at a time, with what to do about each.
Why is my new concrete already cracking?
New concrete shrinks as it dries, and shrinking makes cracks. Fine hairline cracks in the first weeks are common and mostly cosmetic. Cracks that are wide, that run across a slab instead of along a joint, or that have one side higher than the other point to missing joints, a poor base, or too much water in the mix.
Is the contractor responsible for a crack that shows up weeks later?
The contractor is responsible when the crack comes from the work: joints left out or cut too late, a thin slab, a soft base. A hairline shrinkage crack is not usually treated as a defect in the trade. Read your contract for what it says about cracking, take dated photos with a coin for scale, and raise it in writing.
Why does my new concrete have dark and light patches?
Dark and light patches mean parts of the slab dried at different speeds. Shade from the house, a tarp that touched the surface, wet leaves and uneven troweling all leave marks. Most of this fades over a few months as the slab dries out. Blotches from two different truckloads, or from calcium chloride added in cold weather, can be permanent.
What happens if it rains on fresh concrete?
If it rained on fresh concrete in the first hours, the surface may be weak, dusty or pitted. Rain after the surface has been finished and has stiffened does little harm, and a light rain later helps curing. Summer thunderstorms build fast here, so a crew should have plastic sheeting on site and should not start a pour under a clear storm warning.
There are footprints, rough spots and low spots in the finish. Is that acceptable?
No. Footprints, trowel marks and a wavy surface with low spots that hold water are finishing defects. Small birdbaths can sometimes be ground or filled. Marks across a large area cannot be made to disappear, and you can fairly ask for the section to be redone or for a price reduction.
Are control joints really necessary?
Yes. Control joints are planned weak lines that tell the slab where to crack. Without them it picks its own places. A common rule is a joint spacing in feet of two to three times the slab thickness in inches, so a 4-inch slab has joints every 8 to 12 feet, cut to about a quarter of its depth.
The contractor says he will saw-cut the joints a week later. Is that right?
No, a week is far too late. Joints should be saw-cut as soon as the concrete can take the saw without ravelling, usually within 6 to 18 hours and sooner in hot weather. By day seven the slab has already cracked wherever it wanted to. Ask for them to be cut the same day or the next morning.
I found out my slab was poured without rebar or mesh. Is that a problem?
It depends on what was promised and what the slab carries. Plenty of patios and walks are poured without reinforcement and do fine on a good base with proper joints. A driveway, or any slab where the quote listed mesh or rebar, is different. If you paid for steel and did not get it, that is a breach of the contract. Put it to the contractor in writing.
The surface started flaking after the first winter. Why?
Flaking after the first winter is scaling. It is the most common defect in new concrete in New Jersey. The usual causes are concrete ordered without air entrainment, water worked into the top during finishing, a pour late in the fall that froze before it gained strength, or deicer used in the first year. The first two are the contractor's doing.
My new stamped concrete is slippery. Can that be fixed?
Yes. Stamped concrete turns slippery when a glossy sealer goes on with no grit in it. The fix is to recoat with a sealer that carries a fine non-slip additive, or to strip the sealer and apply a lower-gloss one. This matters a lot here, because a sealed patio with a film of ice or wet leaves is dangerous.
Why is my stamped concrete fading, cloudy or peeling?
A cloudy or white haze means moisture is trapped under the sealer. It happens when sealer goes on too thick, onto damp concrete, or in humid weather. Peeling follows from the same causes. Fading is the sealer wearing away under sun and salt. A solvent wash can often re-melt and clear a cloudy sealer. Bad cases are stripped and resealed.
The stamped pattern is crooked and uneven. Should I pay the final balance?
Raise it before you pay the final balance, in writing and with photos. A pattern that drifts off line, shallow prints and mismatched seams are workmanship defects that cannot be patched invisibly. Holding back a fair amount until the two of you agree on a remedy is normal. Refusing to pay anything can put you in breach, so keep it proportionate.
The crew left ruts in the lawn, washout and splatter. Who fixes that?
The contractor does, unless the contract says otherwise. Ruts from buggies or a truck, concrete washout left in the yard or the gutter, and splatter on siding, doors and the neighbor's wall are all part of cleanup. Rinsing a chute into a storm drain is not allowed. List the items and ask for a date.
What can I do if the contractor will not come back to fix it?
If the contractor will not come back, send a dated letter or email that lists each defect, attach photos, and give a reasonable deadline. Keep the contract and proof of payment. In New Jersey you can file a complaint against a home improvement contractor with the Division of Consumer Affairs at 1-800-242-5846 or 973-504-6200. Small claims court and the contractor's insurer are other routes. This is general information, not legal advice.
If someone else poured it and you want a second opinion, call (917) 909-5931.