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DCM
Drywall over tub flange

Do you have to place the drywall over a tub flange and why.is it okay to stop just above the flange? Tile will be installed down to the flange and caulked.

A. Spruce
Re: Drywall over tub flange

Drywall stops at the top of the flange, the shower surround extends down over the flange and is caulked. Moisture is going to into the flange area, no matter how well you think you've sealed it. If you put drywall all the way in there it would wick the moisture and cause severe mold problems and wall degradation.

LeonardHomes
Re: Drywall over tub flange

Yes, as A.Spruce mentioned the substrate stops at the flange.
To add , drywall ??
Hopefully it's not regular drywall .

A. Spruce
Re: Drywall over tub flange
Ernie_Fergler wrote:

Any other drywall than MR board would be a code violation, in most cases, correct?:D

It used to be MR (moisture resistant ) which is/was green, referred to as green board. I believe that today's code requires at least blue board which is both mold and moisture resistant.

IMHO it's just another new fangled product to lighten your wallet ... :rolleyes:

DCM
Re: Drywall over tub flange

No it will not be regular drywall. I'm asking because the instructions for the tub showed the substrate over the flange [with shims] down to the horizontal tub sides but the opening was 61 inches and with 1/2 inch substrate front and back comes to 60 inches [the width of the tub frame.] Mike Holmes of Holmes on homes of HGTV says it must extend down over the flange to be done right. There will be about 1/2" to 3/4" of the tile that will not have mastic because the mastic will not adhere to the porcalin. to have the substrate over the flange I would need to fur out the studs surrounding the tub but this bump out the wall and would not match the rest of the bathroom wallboard. this is a cast tub with porcalin finish and no wall surround.

A. Spruce
Re: Drywall over tub flange

I've seen it both ways, to be honest, and when the substrate goes over the flange it creates a noticeable "bulge" which will also telegraph through any surround material you use, with the exception of wet set tile. Then you also have the wicking problem as noted before. If you want to go over the flange, then I'd recommend shimming the entire wall to the face of the flange rather than just bending the drywall over it. I'd also recommend that you barely lap the flange so that wicking is not an issue.

JLMCDANIEL
Re: Drywall over tub flange

The blue board goes over the flange but stops ½" above the tub. This provides proper backing for the tile and the ½" gap prevents wicking.
Jack

Sombreuil_mongrel
Re: Drywall over tub flange

Are we talking about a tub without an integral surround? Just a tub, right?
So drywall down to the tub flange is not the greatest idea; the only product to make that situation have any possibility of success is Kerdi membrane to waterproof it, but even then it's better to use a wallboard that will not break down when wet, like Durock cement board.
Now, another snag, you said mastic, I heard you so don't deny it! Mastic is a very very bad thing for tub surrounds and showers. You will be doing the job over again very shortly, because all the tiles are guaranteed to fall off if you use mastic (or premixed thinset, for it is mastic + sand). You must, must, must use the proper thinset, determinant upon what kind of substrate and what type of tile you are working with. Thinset is made in many formulations from unmodified, which is just portland cement plus very fine sand, and the variations are created by adding various acrylic or other resins to the mix either in the dry mix or as a liquid additive. The more highly-modified, the longer it takes for them to set; plain portland will set without the presence of air, because it is a pure chemical reaction. Modified thinsets however DO require air, and if applied over a membrane or impermeable material (Redguard, etc) they would require months to harden. Stone tiles demand an unmodified thinset to avoid the bleeding out of the resin to the stone, which causes a permanent stain. White marble has to be laid in white thinset for a similar reason; a grey mortar would reflect through the white tile, resulting in an unsightly condition.
Similarly, white mortars are called for under most transparent glass tiles that are not lined.
You must get some straight answers and good free advice from your tile supplier as to what materials are appropriate for the job.
S_M

DCM
Re: Drywall over tub flange

It is just a tub alone. I will apply the appropriate "glue" for lack of better terms. I was just not sure if i MUST go over the flange or not. Like I said the instructions showed an illustration of substrate material over the flange and stopping just above the top of the tub. thanks for your help.

JLMCDANIEL
Re: Drywall over tub flange

Sombreuil_mongrel, while your dissertation is interesting I would like to point out it was off topic and while "mastic" does have a specific definition it is commonly used as a general name for any material used to stick things together. Just like Channel locks is used as a common name for water pump pliers and Scotch Tape for any brand of cellophane tape. We must all make some allowances for non professionals rather than getting snippy.

Jack

Sombreuil_mongrel
Re: Drywall over tub flange

Whenever I hear someone is planning to drywall a tub surround, then use mastic to adhere the tile, I move into emergency intervention mode, because these are two things that should never happen independently, much less in tandem.
If you ask for tile mastic, that's what you will be sold. Thinset is not mastic, for cryin' out loud, even though it's used to stick something to something. In tiling nomenclature "mastic" is a specific material, not a generic term.
I was being coy at times, and opinionatedly emphatic. I need to mellow out more, I guess. It's no skin off my nose if he uses rabbit-hide glue for his tile.:rolleyes:
S_M

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