Concrete Slab Issues in 10 year old home

Hello, first time post here.

Just purchased my first home in Southern Ontario in a hot real estate market. Unfortunately, could not do a home inspection in this market due to the crazy high bidding wars.

In any case, I have a home that has basement slab cracks that look abnormal to me. There are also dried water marks, which I never noticed before because the previous owner had covered it with rugs. Images can be found here: Basement Water Marks and Cracks - Album on Imgur

You can see the displacement from the leveler, the slab is not completely flat. In addition, the water marks to me suggests a high water table causing hydro static pressure. I do not see any water marks on the walls, or any signs of mold. I also called the previous owner, and she told me that out of the 5 years shes lived there, there hasn’t been a basement flood (not sure if I believe her though).

Is this something to be concerned about? The cracks definitely are not hairline.


Interesting… you are now the third owner of a ten year old home. Why do you think that is?

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I live in Ontario. I have completed over 3K home inspections in 10 yrs. What you are seeing are marks left from the smoothing ( floating) of the concrete, not water marks. Cracks are not an issue. Basement floors are never level. They are sloped (slightly) toward the drain.
Secondly: The basement floor is not structural in any way. The slab is poured after the home is built and plumbing drains are installed. You have nothing to worry about!
Hope this helps


It is unfortunate that you made the biggest purchase of your life without having a professional inspect it for you. It is a complete fallacy that you would loose out on a house if you got a home inspection.

BTW I wouldn’t want a house where the seller choose the offer without a home inspection.

I would suggest hiring a professional inspector to find out what other issues there are with this house.

To your question:

First rule is concrete, it cracks. It actually starts getting microscopic cracks before it is sufficiently set to walk on. Concrete cracks where it wants to, most often at corners. A good concrete contractor will put control joints in to “control” the location of the cracks for aesthetic reasons only.

The “watermarks” are float marks as Doug stated because the finish is not professional.

If your concerned about the slab contact a local inspector, engineer, or concrete contractor to inspect it for you.


Just like mentioned: a large enough slab without control joints will crack at random locations. Make some markings and take some measurements. If it does not get worse progressively, it’s not a major concern. Keep in mind, the basement’s floor is normally not a structural component.

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Tony: The current reality in the Ontario real estate market is that sellers don’t accept offers with conditions like an inspection. Almost every sale involves offers over asking price. I’ve seen sales for 100-200K over asking price. I know it is crazy but that is the reality. Further, float marks are as common as cracks, not an indication of anything unprofessional. If I may---- don’t be so judgmental.



That pretty much says it all above.
The marks on the floor are from finishing the floor with hand trowels. To finish a floor with a trowel machine, it takes longer to finish, because you have to wait until it gets hard enough. Finishing by hand will finish quicker but leave those marks if not hard enough.
Or, they just did not bother at all with a machine. LOL

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Welcome to our forum, Jeff!..Enjoy! :smile:

In my experience concrete expands and contracts. You not only need control joints, but also an expansion membrane like felt around the perimeter against the footing.

Don’t you just love it when non-member guests come on the forum, ask questions (get free advise) and never return or acknowledge the response they get. :poop:


Hi Doug,

Sorry for the late response, it’s been hectic with work. I definitely appreciate everyone’s response! As a first time home owner, it definitely puts my mind at ease. I’m still going to go with a home inspection, to see what else I have to fix, if any.


The housing market has been insane this year. We were outbid on multiple homes, some of which had 15 bids! Unfortunately, removing the home inspection condition was the only way we could get in (at least according to my realtor).

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I’m still going to go with a home inspection, to see what else I have to fix, if any.
Good plan