Almost ready to start putting in greenboard and cement board, but have a question.

[NoviceLurker]

Bathroom is almost ready to be boarded. In the shower, cement board (Fibrock) will be the walls, the ceiling will be greenboard. How do I do the transition with taping the seams where the walls and ceiling meet? Thinset is used for the cement board, but using thinset for the cement board/greenboard corner will make the greenboard have a rough texture. How should this be handled? And also the exterior corners.

 

[wwhitney]

Greenboard is basically useless. It's sold as being more moisture resistant than regular paper faced drywall, but the difference is minimal. If you're that concerned , use a paperless wallboard (fiberglass facing, I think). As it's much rougher than paper, it will need a Level 5 finish (skim coat).

Also, if I recall, the greenboard instructions may prohibit its use on ceilings. I believe it is less stiff than regular drywall. Personally, if it's not a steam shower and you have proper ventilation, I'd just use regular drywall outside the shower zone.

As to Fiberock, it's not a cement board, and although it's rated for shower walls, I'm not a fan. Its core is gypsum and cellulose, so it will be damaged if it gets wet. Its longevity depends on maintaining a very good waterproofing layer on the surface of the board--every screw hole and every joint needs to be properly waterproofed. I'd prefer a board with a foam interior like Kerdiboard or GoBoard; then at least if the interior gets wet, it won't get damaged [still not something you want to have happen, as you don't want the water getting through to the framing.] Or you could use cement board with a topical waterproofing.

Cheers, Wayne

 

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[NoviceLurker]

Greenboard is basically useless. It's sold as being more moisture resistant than regular paper faced drywall, but the difference is minimal. If you're that concerned , use a paperless wallboard (fiberglass facing, I think). As it's much rougher than paper, it will need a Level 5 finish (skim coat).

Also, if I recall, the greenboard instructions may prohibit its use on ceilings. I believe it is less stiff than regular drywall. Personally, if it's not a steam shower and you have proper ventilation, I'd just use regular drywall outside the shower zone.

As to Fiberock, it's not a cement board, and although it's rated for shower walls, I'm not a fan. Its core is gypsum and cellulose, so it will be damaged if it gets wet. Its longevity depends on maintaining a very good waterproofing layer on the surface of the board--every screw hole and every joint needs to be properly waterproofed. I'd prefer a board with a foam interior like Kerdiboard or GoBoard; then at least if the interior gets wet, it won't get damaged [still not something you want to have happen, as you don't want the water getting through to the framing.] Or you could use cement board with a topical waterproofing.

Cheers, Wayne

Greenboard is the mold tough that’s at Home Depot. I grew up calling it “greenboard.” Entire inside of shower will be RedGard liquid membrane.

 

[Jadnashua]

While paint-on waterproofing can work, I much prefer to use a sheet membrane or something like KerdiBoard. A pail of RedGard big enough to do a shower properly is about $150 give or take a little. You have to put two coats on, wait in between, ensure that your coat has the proper wet film thickness, there are no pinholes, or runs. Too much is just as bad as not enough.

Actual green board needed supports closer than the typical 16” OC, otherwise, it would potentially sag between them. Double check the specs on the board you want to use. For most situations, plain drywall with a quality paint coat is more than enough for a ceiling anywhere in a typical bathroom.

 

[wwhitney]

Greenboard is the mold tough that’s at Home Depot.

"Mold Tough" is apparently a line from USG's Sheetrock division. It includes both paper faced and glass mat faced wallboard. So that doesn't clarify which product it is.

The paper faced products are rated for 16" o.c. supports in ceilings, per the spec sheet (although the 1/2" product has to be applied perpendicular to the joists if a "water-based texture material" is to be applied.) So given that, I guess I don't see much downside to using "Mold Tough", just no real upside unless it's the glass-mat version.

Cheers, Wayne