The bathroom wall (with the shower/tub) is against a bedroom. Should their be a double vapor barrier, one against the bedroom wall with the pipes in-between with (insulation sandwiched) with pipes? Or just one vapor barrier on top of studs against the cement Durarock board with the thinset/tiles and grout over the single vapor barrier? Or just one vapor barrier against the bedroom wall then insulation? Does this wall need to be insulated?

The old insulation was severely laden with mold but then they used regular dry wall which mostly totally disintegrated... with the paper face against the drywall then facing the tiles in the shower. Needless to say the drywall was almost totally gone, the wall washeld up by only the tiles and grout...

One layer of vapor barrier only placed on the studs under the wonderboard and tile. Insulation is optional and only for sound.

Does the landlord need to keep the tentant knowledgeable of how long ago the carpter was first installed in apartment?

thanks. However... the variable single lever water mixing units currently on the market have been on numerous multiple occasions (expensive Moen's too) have leaked considerable amounts and destroyed walls on both sides. While the "normal" might be to install a single barrier (as described) I thought it might be "safer" to install a second on the bedroom side as the wall itself is an old "batten and plaster" type from the 1890's, destroying a wall of that type would with water damage would necessitate an incredible "replacement cost and specialized repair". Therefore I suggested the "extra" plastic barrier be considered in this specialized incidence.