Basement offset crack

Hi all,
I’m looking at purchasing a home, and I looked at it today and found a crack in the basement running along the front wall of the home (see sketch and picture below).

The home is two story, 3 side brick built in 2006. When I pounded on the floor with my fist, the lower portion next to the wall sounded very solid (as expected). However, the interior/raised portion of the floor next to the crack sounded slightly more ‘hollow’ for lack of a better descriptive word.

The crack is about 1/8" or 3/16" vertical displacement as my best guess at the worst spot. I can’t tell how far the crack extends (note the carpeted areas in the sketch), but it did appear to get ‘better’ as it was heading toward the carpeted areas so it looked like the worst part was exposed, as shown in the picture.

Is this a big problem that I should stay away from?

The crack in in the basement floor Correct?

Cracks in basement floors are not generally a problem.
Your taping on the floor near the wall will always sound more solid than taping on the floor away from the wall.
There is likely a footing near the wall and gravel under the concrete, away from the wall.

You don’t say where you are located or how deep the basement is.
The displacement could be from frost (if the basement is not deep enough, below the frost line) or slight settlement.

I would monitor the situation and if it becomes worse, further investigation may be warranted.

Hope this helps


Yes, the crack is in a finished basement floor (AC/heated space). The crack is about 8" from the front plane of the house (the wall in the original picture above is the front exterior wall of the house). This portion of the basement is below ground, however not all of the basement is below ground. The intersection of the highlights below show approximately where the crack is located on a larger scale, and it’s running parallel with the front plane of the house. This particular section of basement is approximately 6’-ish underground if I had to guess. The porch is a wooden structure attached to the front of the house. The crack is arranged in such a way that the front wall of the house is sinking, or the interior of the house is ‘heaving’ upward relatively speaking.

At some point in the last few years (home is approx. 5 years old) a drainage system was installed (underground routing of gutter drainoff to sewers); it’s unclear what prompted this (not sure if it was to remedy a serious problem, or the previous owners just wanted it). Realtor seemed to believe this was aftermarket and unusual in some way.

I’m looking at this home prospectively to buy, so I’ve got no opportunity to monitor for a year and re-evaluate later. What are some indicators I could look for that would alert me as to whether this might be a problematic active crack? If this does continue to get worse, what sort of repairs would remedy this, or should I not expect it to be a structural problem long term?

I suspect the crack is from improper compaction of the soil.
You would be best served to simply call a knowledgeable home inspector…while we gladly can offer advice, without actually being there the advice is very limited and quite frankly may be incorrect based upon limited information provided. I believe this is also the same house that had the crack above the garage door (right elevation).

Hopefully it isnt/there wasnt an interior drainage system previously installed eh.Something like this…see jagged edge of floor

If the crack were due to uneven underlying support, due to moisture (John) or inadequate compaction (Jeff), There would have to be downward pressure to cause the slab to crack along the line if differing support (where the edge of the underlying void was).

Was the plane of the vertical displacement lowest on the side of the crack nearest the wall, indicating that the weight of a bearing wall caused the concrete to fracture along the edge of differing underlying support?

Didnt say it was from moisture, just said that when these inside system DINGBATS j-hammer/break up edge of floor, the floor will often look as it does in the photos,see green painted floor 6-8" off wall/link posted....similar to Eds pic,thats all…got milk?

I didn’t notice any moisture or signs of moisture in the area (no stains on the wall/floor), but I did not closely examine the outside of the wall in this area.

Yes, this is exactly what I was intending to say in my earlier post. The crack is such that the concrete floor attached to the exterior wall was lower (elevation) than the interior of the house; indicating that the weight of the wall and it’s attached members have ‘dropped’ further into the ground.

Why? I’ve got no clue really… compaction seems like a pretty reasonable guess. A compaction issue would eventually come to equilibrium and stop (I’d guess), whereas some sort of washout/drainage issue would keep going and just get bigger maybe. With this being 6’ under ground it seems unlikely to be drainage related… all that sound right?

The elevation difference (about 3/16" maybe?) seemed localized to one short spot a few feet wide in the center of the house; but as it heads toward the outside corners of the home (carpeted areas in the first picture) the crack appears to subside (although it’s being covered by carpet so I can’t see for sure what’s under there).