Horizontal Concrete Wall Crack

[stiffener]

We conducted an observation of an 8" by 5'-0" continuous foundation wall recently and observed something that we had not seen before. We observed that the wall has horizontal cracks approximately 3" from the top of the wall on both sides. The wall is approximately 40' long, but the cracks don't appear along the entire length. The wall appears to have been placed directly on ledge on a very steep site. This foundation wall makes the front wall of a unheated crawl space with low and balanced back fill on each side. Both the foundation wall and wood framed wall above checked as plumb. We observed no diagonal or vertical cracking. There is a large cantilevered deck above the wall and we originally thought the damage might be from uplift, but we observed no damage or separation to the wood wall framing, which is all exposed, and the building has no tension resistance system in place other than the exterior sheathing. There is no visual damage to the finished residential space above. So our working theory is that the reinforcing along the top of the wall is corroded due to chloride in the concrete mix design. There is no water staining/damage or visual corrosion that we would normally see. We are wondering if anyone else has seen damage similar to this.

 

[briancpotter]

Seconding that this looks like some sort of movement/settlement crack to me. I'd expect to see more staining if it were corrosion-induced spalling.

 

[BAretired]

There appears to be no gap between the top of concrete and the double wood plate. The anchors for the wood plate are not long enough to prevent the formation of the crack seen in the photo. Might be a good idea to talk to the contractor and find out the sequence and details used to construct the wood wall above. Perhaps the upper few inches of concrete is hanging from the wood wall.

BA

 

[bones206]

It's hard to tell from the photos, but the upper concrete seems to have a lighter, chalkier appearance relative to the lower concrete.