Honestly, everything else about the house is very well done so it does seem odd that they would get that sloppy here. There is some rubble and a bit of moisture in the photo. It's possible that rodents dug the rubble out but the moisture is from a leaking hot water heater (this has distracted my DIY energy over the Christmas break [I actually made a hilarious "lazy river" with vapor barrier that flows into a bin and an auto-siphon to drain it outside so we could have showers and dishwasher over the holiday]. All to say that moisture is coming from a know source.
I was wondering about that.. lt wouldn't drain anything out of the basement, based on its position. It's not between 2 structures (is is part of an addition, but that was done at once). Maybe there is an air gap necessary when they put down the vapor barrier and concrete over the bedrock? Perhaps to let air in so that water underneath can drain away?
[edit: grammar]
Vegetation OP t1_j1xnrv8 wrote
Reply to There's a weird gap in my foundations and I want to fill it. Its packed with stones ATM and there's big spaces between them. How would you create a moisture barrier here and seal it? by Vegetation
I'm coming around to the "this is supposed to be here" possibility. What sub would you post to get folks thoughts on what this might be for?