While building a strip foundation (a concrete wall starting several feet below ground) I have to insulate it from moisture because otherwise moisture will get into the foundation and into the basement. Insulating the sides is relatively easy - once the wall is there I can glue some stuff like ruberoid onto the wall or paint it with resin.
What about the foundation wall bottom? I cannot paint the wall bottom or glue anything to the wall bottom before the wall is there and once the wall is there it's pressed hard onto the ground and I cannot do anything with its bottom. This is kind of chicken-and-egg problem.
How is moisture insulation done for the strip foundation bottom side?