Homeowner notices foundation crack spreading before basement work, and builder warranty could be involved

"The crack itself isn't the issue — it's the fact that it's widening."

An Ontario homeowner says they are worried after spotting a growing crack in the home's foundation, claiming the gap expanded by nearly a quarter of an inch over the course of a month.

What happened

In a Reddit post on r/homeowners, the poster included two photos to show how the crack had changed. They asked, "Wondering if someone can help tell me if this is a concern that I should take up with my builder?"

The first image showed the crack as it appeared a month earlier.

The second was a closer view, with a coin used for scale to illustrate the depth of the gap.

The homeowner said the damage was in the basement, noted that there had been no rain, and added that the home came with a seven-year structural warranty.

One commenter said the issue was less about the crack itself and more about how much it had spread, advising the homeowner to have the house professionally evaluated and to pursue a warranty claim.

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Other users said cracking can happen as newer concrete settles, but they still thought the visible change between the photos was worth recording.

One person wrote that during the first few years, houses often crack and shift as they settle, and that without moisture intrusion there may be little reason for alarm. Another replied that while cracking in concrete is common, this example looked like it was separating and should be examined closely.

More context

Because the problem was found in an interior basement slab in a newly built home, rather than in a driveway, patio, or garage floor, the discussion focused more on warranty coverage and inspection than on a simple cosmetic repair.

Several readers pointed out that the crack was near a corner. One said cracking at a corner is common, and noted that if the slab is nonbearing, the damage may not be structural even if repairs are still needed.

Another commenter mentioned control joints, which are designed to guide cracks into specific areas, and said this did not appear to be one. A crack away from a control joint can raise different questions about settlement and slab movement.

That same commenter suggested a builder might reskim the floor, though the crack could return if settling continues.

The homeowner also said basement finishing was already planned, which raised concern about losing sight of the area once the work was done. "I'm concerned a bit as they are working on finishing the basement this month. I won't be able to see anything after that," the poster wrote.

What should be done

The strongest advice in the thread was to alert the builder before any more basement work is completed.

After one commenter noted that the home was new enough that the builder may be responsible for fixing it, the homeowner replied that they would reach out.

People also urged the homeowner to document the widening carefully with photos and to watch for any other changes elsewhere in the house.

One commenter asked whether any doors were sticking and whether there were visible cracks in the walls. The homeowner said the doors still seemed fine and planned to check the walls next.

Another reply stressed that since the house was still in its first year, everything should be covered under warranty and the builder should be able to inspect, document, and arrange repairs if needed.

Even commenters who were less alarmed generally agreed on the same approach: report it to the builder, get it documented, and have it assessed before flooring or other finishing work hides the area.

Related reading

A visible crack can mean more than a cosmetic flaw, especially in a newer home.

• In Lake Las Vegas, retirees were sent to arbitration over cracking homes after severe damage threatened their investment.

• In the UK, buyers are warned to keep an eye out for knotweed that can damage foundations.

• Homeowners are following a growing trend that's putting properties at risk, and the damage can bring costly repairs.

• Across the United States, insurers warn of an uninsurable future as property risks and costs keep rising.

• In Morocco, architect Aziza Chaouni is advancing earthquake-resistant house design that could replace thousands of vulnerable homes.