Concrete cracking above plumbing pipes

Hi folks:
In my latest inspection, there are cracks in the concrete right above plumbing piping. My assumption is these are compression cracks caused by the plumbing being too close to the surface of the slab.
I would like to know some seasoned inspector’s opinions. This home is used three weeks a year. It has the heat turned off during the winter. A part of me thought these cracks could be from freezing standing water in the waste lines, but the plumbing seems to be well done through out the home and I don’t think that is my concern.
The cracks shown in my photo are from the basement shower to a drain line and the main sewage line leaving the home.
Should I be concerned about the condition of the waste plumbing pipes? IMG_1145|375x500 IMG_1149|375x500

Meant to say expansion cracks

Plumbing does not typically cause slab cracks; settlement, upheaving, and concrete shrinking does. Basement slabs are notorious for cracks, especially when installed without control joints and such. It’s hard to assess what’s going on with the limited information and from the picture alone. You would need to investigate the surroundings around the crack to see if there is any differential movement in the slab, walls, etc… to see what could have caused it to crack. For example, if a corner of a slab settles, it can create a crack but then the slab in that area would be uneven… with experience you can see that the slab had settled in one area and not the other, causing a fracture in the slab. If everything appears normal, it’s most likely just a concrete shrinkage crack. Basement slabs are typically none structural.

1 Like

were there any control joints cut into the slab ?

Looks like there’s something going on with this tile and mortar joint:

1 Like

There is a footing and normal structural foundation walls. This slab is not structural. The pipes literally start and finish at either end of these cracks. The shower crack goes in a diagonal from the drain to where the clean out is and the larger crack goes from the sewage clean out to where I
can see the clean out for the septic tank outside.
I know this is non standard, that is why I don’t exactly what to do.

No control joints

Nothing’s going on there, that’s the way it was installed. It is angled in the area you circled. It’s not a straight line of tile.

It may not be from water freezing in the pipes and expanding to crack it, but just the temperature difference in the slab where the pipes are, causing the slab to expand and contract at different rates.

It’s always possible that the line does not have much cover over the pipe and could be slightly in the bottom of the slab due to elevation.
It is not a crack I would be worried about and just note it as it is and move on.

concrete slabs without control joints are going to crack, just the nature of the beast…

Concrete does not expand in a garage. It shrinks. Isolation/control joints are provided.
One hypotheses, poor aggregate compaction.

The first image looks like plastic cracks. Plastic settlement cracks are so-called because they form while the concrete is still plastic form and has not set. The settling concrete is restrained and cracks form at the surface.

The second image looks adverse. Like the slab is pulling away, heaving or settling.

Did you use a 24" inch level on the surface of the concrete placed directly perpendicular between the crack to look for indications that the slab is level and not heaving or settling?

Lets see what others have to say.

OMG… … …
Marcel try not to have a conniption… … …

Thank you for this image. Thank you everyone for your input.

Thank you for sharing with us, Kaitian.