House Slab - Cracks

[Ian6233]

Hi all
We are building a new house and I work away for long periods. This trip home I noticed a crack in the kitchen area that to me looks quite alarming.
Crack is about 1mm wide and runs for approx 4 meters from the fridge recess to the external doorway.
Cannot tell if the crack is stable or still growing.
We plan to install large 900 x 600 tiles through this area and I am worried that they will crack down the track if the concrete continues to move.
Has anyone had any experiences with house cracks before.
Should I be concerned
Builder says that these are settling cracks. Easy answer from them.
First post so I hope the photos attached OK

Thanks
Ian H

 

[JedClampett]

That's a pretty serious crack. Without more details it is hard diagnose. It might be settling or it might be poor workmanship or it might be something else. If it continues to move, you will have tile issues. But you know that.
You could monitor it, but that will delay completion. You might want to hire a structural engineer.

 

[hokie66]

I doubt if it is due to settlement. Looks more like a drying shrinkage crack. Without more information about the plan, it is tough to say.

 

[Ron]

Agree with hokie66 that it is likely a drying shrinkage crack. There does not appear to be faulting, so settlement is not likely. There is a slight indication that at least part of the crack occurred while the concrete was plastic.

Not uncommon in residential construction. We need a bit more information about the orientation of the crack and perhaps a sketch of the area, including the crack, and the surrounding concrete slab features.

There are several ways to mitigate such a crack, even when installing tile above. Please provide more information/sketches/photos so that perhaps we can help.

 

[dcarr82775]

Ron,

I am intrigued, what are the visual indications that a crack occurred while the concrete was plastic?

 

[Ron]

dcarr....see attached. Plastic shrinkage cracks occur in short, discontinuous groups. It is likely that there were other that ultimately interconnected to create the main crack, with the one lone piece that was superficial and one end was not deep enough to be interconnected.

 

[darthsoilsguy2]

it sounds/looks like shrinkage cracks... another good way to tell is to draw the crack on a layout of the slab pour... did it occur at the thinnest section? the fridge nook would have a spot where 2 different slab widths meet.

 

[hawkaz]

Bottom line- It is a crack. Concrete cracks.
Per the original post- Cracks will translate through the tile unless it is stable and has been properly prepared for a new surface on top

 

[bb29510]

your surged is uncomplicated and settlement has started

 

[bb29510]

your subgrade is uncomplicated and settlement has started

 

[Ron]

bb29510...this crack has nothing to do with settlement or compaction...it is drying shrinkage.

 

[rapt]

Drying Shrinkage by the look of it, not plastic shrinkage.

How long since the concrete was poured and how was the slab reinforced?