Vapor barrier in bathroom (foundation, heating, cleaning, mold)

[frecny]

All of the walls of our bathroom are interior walls. We were redoing the shower from the 1970s, there is no vapor barrier behind the tile and there is no water damage or mold.
We are using Durock cement board then thinset then tile. Is a vapor barrier needed?
They seem to be a recent thing. 40 years (when the old bathroom was done) they didn't use them and there were no problems for 40+ years. (believe it or not, they also used sheetrock with not problems!)

Ideas?

[TrapperL]

I do about 8-10 tear outs a year where folks have used the cementious board only to have the water proofing fail. These types of backer for tile are not water proof and don't even slow it down. So yes, if you intend to use this type of backer board, you'll need to use a water proofing behind it. The normal around here is felt. Felt with time deteriorates as does any 6mil plastic. DO NOT assume that thinset will stop water as it commonly fails.
We replace the backer board with GPs DensShield which is a fiberglas covered water resistant drywall. We screw it and then float it just like any other drywall instead of the recommended adhesive that is water resistant. Then we brush on 2 dry coats of Redgard which is a water proofing. Note, there is a major difference between water resistant and water proof. I've never had any of my work leak and should the foundation move some, the Redgard will flex as it's like a coating of rubber. My shower installs do not leak and I warrant them for as long as you own the home.

[RayinAK]

I still use a vapor barrier. DuRock and Thinset are still porous. Backer-board is not as porous as Durock, but it's more expensive.

[K'ledgeBldr]

Originally Posted by frecny

All of the walls of our bathroom are interior walls. We were redoing the shower from the 1970s, there is no vapor barrier behind the tile and there is no water damage or mold.
We are using Durock cement board then thinset then tile. Is a vapor barrier needed?
They seem to be a recent thing. 40 years (when the old bathroom was done) they didn't use them and there were no problems for 40+ years. (believe it or not, they also used sheetrock with not problems!)

Ideas?

The tile surround debate is just that- a debate. And it's because people usually don't put 2 and 2 together.
Back in the late 40's, through the 50's and 60's housing was going up at a fire storm rate. They were like Swiss cheese to air infiltration. Energy was cheap, so we compensated by bumping up the t/stat.

Housing that has been built in last 20yrs is much tighter. Much less air infiltration, more insulation- meaning less use of energy for heating and cooling. All of these and a rapidly changing and more diverse climate are the factors that drive the moisture/mold problems we see today.

That old saying "they don't build them like they use too" can go both ways. So, just because you don't see mold in a 40-50yo house doesn't mean is was better, it just means the moisture didn't stick around too long.

[frecny]

Some good advice. What do you think about grout sealers? Are they worth the time and money if the grout and caulking are done correctly when the tile is finished?

[K'ledgeBldr]

Grout sealers are great from a cleaning aspect-
I don't see much of a difference when it comes to water intrusion.