We are renovating, and right now the entire floor is gone, and we have good access to the foundation. The house is on a glacial ridge, it's insanely dusty and super dry in the foundation. We have plastered the foundation, so it is tighter now than before.
We have removed sawdust and pieces of wood and dug out about half a meter, but there is still sawdust mixed with the gravel that can't be removed due to how mixed it is.
So the question is, in this super dry foundation that stands on naturally drained material, how should one think about using plastic here?