Thread: Sunken Slab

Not quite sure what to make of this. The pics below are from the crawlspace area. You can see the slab floor is cracked and sunken in a couple pics and the mortar joints between the concrete blocks on the wall above the sunken slab are ridiculously wide.

It appears repairs may have been made to the wall as none of the other wall sections in the crawlspace has mortar joints this large. Or it's just really sloppy work. The floor had some mortar patching which had cracked and separated since being put in so whatever is happening with the floor appears to be ongoing.

The main water service entrance line is directly above the damaged slab so it's possible a water leak had gone on unchecked (and may still be going on inside the wall) for a long enough period to cause erosion beneath the slab. There was no visible evidence of active leaks in the area during the inspection and the exterior spigot and plumbing line were no where close to the damaged section of slab. If any plumbing line is the culprit, it seems to be the main water entrance line.

Thoughts? Recommendations for client? A structural engineer seems like overkill as there really wasn't any cracking or displacement on the block wall. Aside from the king-sized pointing, no other issues with the wall besides moisture staining.

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Nick, Hard to tell from the pics. That's a crawl right. MAbey poured the slab after the floor was in and couldn't compress the base properly.

Originally Posted by Nick Ostrowski

... The main water service entrance line is directly above the damaged slab so it's possible a water leak had gone on unchecked (and may still be going on inside the wall) for a long enough period to cause erosion beneath the slab. ...

I think you got it right.... I don't think it woud take too long to cause that kind of damage if the leak were at the foundation wall -- especially if it was in a area behind shrubs where the occupants wouldn't notice the soggy earth outside...

This may help: