[feeshyLew]

The big room, laundry, and bath is poured cement/foundation. The original portion of the house has a crawlspace, with wood joists... but in order to get the second story in without violating the allowable height in the neighborhood, we had to set the addition down about 3 feet, so ground level. That's because the lot has a slight slope to it, about 5 feet from street to alley. Gives the upstairs some partial views on the ocean though, which is nice.

The master bath is upstairs. There we painted on a waterproof membrane over the flooring. (The membrane is the greenish stuff crawling the walls.) We taped/membraned the joint between the floor and walls too. Then put a layer of thin hardibacker board across the floor as well, with the thinset going directly on that.