There were no vapor barriers in the floor, floorboards were just thrown down without securing them to anything, some of the floor is not even touching the footers.

When moisture is evaporating up though the slab and ultimately through your grout joints you'll get water soluble minerals that are left behind on the surface of the grout, its called "efflorescence", and yes, its very hard to clean.The only ways to avoid this is to check the subfloor with a moisture meter to be sure it's completely dry or installing a vapor barrier over the slab prior to tile. 

Risks: If the government confiscates like they did in the 1930s, paper GLD is vaporized instantly.

Was there a full vapor barrier under the flooring?

Why isn't water vapor included along with CO2.

The tree on this lot also diverts water under the foundation, so we added sand and vapor barrier underneath to keep water from collecting under the house. 

We are using vapor permeable tapes, liquid applied flashings, and corner guards for these openings before setting the windows and doors. 

I usually will put up a vapor barrier over the studs, then concrete board or green drywall, then I use a waterproof membrane such as Kerdi.

If the smoke does bother A and B, maybe you should ask C or D to start using a vaporizer.

Its a vapor barrier, but also insulates and reflects heat as well.