I am tearing out and installing a new bathtub/shower in my house. Above the shower is the attic, and it is insulated but not heated. For the ceiling of the shower, which will not be tiled, do I install greenboard? Do I need an vapor barrier between the shower and the attic insulation? Thanks.

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cbryancu t1_j6mz4m2 wrote on January 31, 2023 at 2:08 PM

#1,659,852

Yes use green board on the ceiling. Yes you need vapor barrier between drywall and insulation. Don't put another vapor barrier between insulation and attic.

magaoitin t1_j6n2zcq wrote on January 31, 2023 at 2:36 PM

#1,661,126

Yes, to greenboard and vapor barrier on the ceiling install. Steam and warm wet air rise and will condensate on the ceiling even with a well-insulated space above.

I go a step further and install a Pre-Catalyzed Epoxy paint on any bathroom/shower that I am doing so that even the taping mud is sealed and mold proof. Might be a waste since the stuff is $50-65 gallon, but it is insurance in my mind.

badwhiskey63 OP t1_j6nmfof wrote on January 31, 2023 at 4:43 PM

#1,667,274

Replying to cbryancu (#1,659,852)

Thanks

badwhiskey63 OP t1_j6nmgir wrote on January 31, 2023 at 4:43 PM

#1,667,280

Replying to magaoitin (#1,661,126)

Thanks

FirstForFun44 t1_j6o01ai wrote on January 31, 2023 at 6:05 PM

#1,671,605

Replying to magaoitin (#1,661,126)

What's the difference / pros and cons of epoxy paint vs redguard? Do you use both? I was just gonna use the waterproofing / redguard but I've never heard of epoxy pint...

TheWindSerfer t1_j6oj4u4 wrote on January 31, 2023 at 8:03 PM

#1,678,008

They make a specific type of wall board for shower areas. Do not use plastic over standard drywall.

magaoitin t1_j6osftt wrote on January 31, 2023 at 9:00 PM

#1,681,444

Replying to FirstForFun44 (#1,671,605)

Redgard is a fluid applied waterproofing and crack proofing membrane that is typically used to seal shower floors and walls where you have installed either cement board or tile backer board. It can also be applied to brick/CMU/plywood. I have never tried to use it on greenboard and don't know if it is warrantied for that application, or how paint would then bond in a ceiling application.

In a nutshell it is a roll-on plastic liner you can put mortar over and then tile. I have also used it on a plywood subfloor, under a LVT in a laundry room to guarantee any leaks/spills/overflows would not get to the joists and subfloor.

Pre-Catalyzed epoxy is a one-part pre-mixed epoxy paint. Most waterproof epoxies are 2-part kits that you have to mix together then apply (messy and a PIA to deal with). to form a hard waterproof coating. Pre-Cat comes premixed and ready to use like standard paints or shellacs, but it forms a harder wear surface and is more durable at sealing, especially on GWB/greenboard. Plus, it can be tinted to color match anything. Even the big box store like Home Depot carry it and mix it. If it is an oil-based system (there are water based as well) and it is difficult to paint over down the road. I guess that is a pro and con. it's hard-to-get other paint to stick to it. It does an amazing job of waterproofing drywall/GWB/greenboard.

https://www.homedepot.com/p/BEHR-PRO-1-gal-White-HP-Pre-Catalyzed-Waterborne-Epoxy-Semi-Gloss-Interior-Exterior-Paint-HP15001/301899214