The plumber busted out the shower floor to do part of the job he was hired to do. Now that it is broken, I see there is a thin black plastic vapor barrier underneath the slab which was poured in 1965. This plastic was also torn when the shower floor was jackhammered out.

Before they re-pour the foundation of the shower floor, should I make sure the vapor barrier is replaced in this area? They said they don't replace it usually, and as far as they know, its absence doesn't cause problems.

However, slab foundations in my region are prone to cracking and the experts say it is due a difference in moisture/dryness in the soil. Many people water their foundations in the dry summer.

I have also noticed that when it is especially wet or damp weather, my concrete slab floor "weeps" (I scraped up all the old flooring to replace it throughout with wood so this is how I can see the weeping.) I don't actually know if the water is coming from underneath and through the concrete or if it is just from condensation above it.

My home's foundation is pretty level right now and I would like to keep it that way. Any thoughts, suggestions or advice?

This home has slab on grade, it's a one level ranch, I just included it in "basements" category because so many homes have the slab in the basement.