This was found by a friend of ours that has a sewer inspection hose (really cool thing with a camera and a light at the end).I don’t understand how the vapor ends up getting past the trap, but it does and smells awful.

If you are building make sure that your buildings have a good air vapor and weather barrier.

I am also having him install vapor barrier in my crawl space(entire sqfootage of the house is ~1600sqft), replace my main sewerage line that runs into my tenant’s place, add in a full bath, and add in 2 small closets. 

Found water in the crawlspace that had resulted in mold that now needs remediation. 2 units need to vacate for 4 days during the remediation per the remediation company (to avoid cross contamination, vapors, and so they can air scrub the 2 lower units). 

Usually stone is attached over the sheathing material with a vapor barrier and wire mess to allow the motar to bed in.I'd be careful about figuring the labor to gently remove it (big hammers are awesome, but in good and bad ways :) It could take some time.I love hardie-plank siding.

Install a proper vapor barrier, either mud or cement board or Shluter the whole enclosure and then throw up the tile, you need to cut it anyway.These guys are full of crap....actually probably crooks.

Her jaw dropped when she saw her balance .

Herbal life had the same scam Renatus does.

Vapor barrier.

In this case you'd see if the tenants were doing things like growing herbal products or other ways of excessive use and put a clause in the agreement that states they will be responsible for the utility reconciliation.