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The very corner of the cement slab, which forms the floor of my basement, broke off. There was nothing supporting it underneath. the portion that broke off forms a triangle 11" x 10" x 14" x 3-6" thick. The chunk was bordering the concrete footings. The dirt in the hole is soft and loose. At least 6 sqft at that corner of the slab is suspended without support. I'm including a couple photos up underneath the slab. I suspect that there is erosion or settlement caused by water. What would be the easiest way to prevent further damage to the structure for as long as possible? My idea is to dig out as much dirt as possible and then pack the hole with rocks. At what point would excavating the loose soil undermine the support of the footings and slab? Thanks for any ideas or insights you are able to provide.

Here is video for context: https://s3-us-west-2.amazonaws.com/flipt-temporary-storage/foundation_hole.mp4

enter image description here photo underneath slab photo underneath

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    The slab is supposed to rest on the footings. Any idea why it isn't? I can't get much context from the photos. Anyway, you'll want to determine whether settling is still occurring, then fill with sand or gravel. Water could help compact it before repairing the slab. "Rocks" are not compactible. – isherwood Oct 17 '17 at 14:50
  • Thank you @isherwood. The slab does not seem to make contact with the footings at all. As far as I can tell, it is floating on the dirt. I might point out that I discovered this problem while filling the gap between the slab and footings with Sikaflex. The house is part of a makeshift settlement built during WWI to support the logging industry. It was probably constructed in whatever way was expedient. By "repairing the slab" do you mean pouring new cement on top of the recommended sand/gravel. Thanks a bunch. – laertiades Oct 17 '17 at 15:33
  • here is a video which may give more context: s3-us-west-2.amazonaws.com/flipt-temporary-storage/… – laertiades Oct 17 '17 at 15:50
  • Yes, that's the repair I meant. Please edit new information into your question body. – isherwood Oct 17 '17 at 15:54
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    I am in the U.S. Everett WA. The house is on a hill. On the East, the slab is about 4' below ground. On the west it is about 6" above ground. The hole is at the SW corner. I will consider removing and replacing the slab. For now, my intention is to leave the hole open through a few wet days to see if I can detect any moisture that might be causing settlement and then base a further decision on that info. I really appreciate everyone's help. This has been very valuable. – laertiades Oct 19 '17 at 14:02

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