# Correct use of moisture resistant Purple board in Bathroom?



## fromscratch (May 23, 2011)

I have a small (30sqrft) bathroom that is stripped down to the studs. I was originally going to put up the moisture resistant drywall everywhere but I have an 8.5ft ceiling and can't find the purple board in sizes other than 4X8.

My question, is doing the whole bathroom in moisture resistant drywall overkill anyway, or is this actually the proper way to do it? 

If it is overkill I'm tempted to do the walls with 10ft regular sheets and just put the moisture resistant around the tub.

Second question, Can I put a vapor barrier behind the purple board?

(Side question does anyone know where I can find either 54" wide or 10ft long purple board in the CA Bay Area?)

Thanks


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## Bud Cline (Mar 12, 2006)

...and you don't want to simply seam it because.......................?


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## fromscratch (May 23, 2011)

What do you mean by "simply seam it" 

I was just thinking with either a 10ft board or a 54" I can keep minimize the joints and keep them all tapered joints.


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## Bud Cline (Mar 12, 2006)

I understand but you will still have joints to repair no matter what, so what would be wrong with and extra one or two or three or four joints/seams?


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## fromscratch (May 23, 2011)

I've never finished drywall before. And I'm trying to minimize the areas I can screw-up. With an 8.5 ft. ceiling and 4X8 sheets would you make a butt joint down next to the floor?


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## Bud Cline (Mar 12, 2006)

NEVER make joints along a door opening. "L"-over.

If it was me (and it isn't)...
I would lay the drywall down holding it about 1/2" to 3/4" up off the floor. Then add a 5" strip above that taper. Then lay-up the second board. You will have to "wide-feather" the single juncture but that's not a big deal I don't think. That way you can get the two seams of the juncture in one pass.:yes:

Some of the drywallers around here may disagree but that's what I would do but I have done it a time or two before.


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## fromscratch (May 23, 2011)

should I try to recess the 5" strip by either using a thinner sheet for the 5" strip or shimming out the 4ft. sheets?


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## Bud Cline (Mar 12, 2006)

*Heck no!*

No reason to screw around with all of that.
What you will have is basically butt-joints but that isn't a major problem. Spread your joint compound in a wide path and I'm sure you can fix it fine.


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## firehawkmph (Dec 12, 2009)

Fs,
Don't worry yourself over taping a butt joint. How do you expect to get good at it if you never try? Patience, not trying to cover everything knee deep in one coat, and using a decent knife or two. It's not that difficult, just takes a little practice. Butt joints just take wider knives. In the time you take trying to find the too easy way out, I'd be done already.:laughing:
Mike Hawkins


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## fromscratch (May 23, 2011)

So just to back up. I should finish entire bathroom in the purple board?

And on one interior wall I will have tile, Hardibacker, Drywall,... Can I put a vapor behind the drywall? 

I'm a bit confused because everything I read says the drywall is not a vapor barrier. But, somehow if I do this tile, hardibacker, drywall, plastic, then I've created a double vapor barrier situation?

thanks


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## Bud Cline (Mar 12, 2006)

Is this tiled-wall in a shower or is it just a decorative wall in the room?


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## fromscratch (May 23, 2011)

tiled shower wall. 

(The other 2 walls will just have tile, hardibacker, vapor barrier). 
The reason for the drywall on the third wall is that I need the extra furring and the wall is shared with a bedroom so I'm hopeful the drywall will provide alittle bit of sound insulation as well.


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## Bud Cline (Mar 12, 2006)

> I'm a bit confused


You think you are confused?

None of your last comment makes any sense. Your shower only has one wall???

In all of your comments you haven't even mentioned a shower until now.

What the heck are you wanting to do?


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## fromscratch (May 23, 2011)

Basically putting up walls in the bathroom.

There is a shower-tub area that will be tiled. (3 walls) Two of the walls will get 1/2 hardibacker with a plastic vapor barrier behind.
On the third wall enclosing the tub I was going to fur out the wall with purple drywall and attach either 1/4" or 1/2" hardibacker. I had some reasoning for this, but it's probably faulty. 
The question was do I put a plastic vapor barrier behind this tile, hardibacker, drywall amalgamation?

Other than that I'm going to go for the purple board on all walls in the bathroom and just take an extra wide knife to the butt joints.


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## Techy (Mar 16, 2011)

if you're putting hardibacker over the drywall you shouldnt even need to finish it


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## Bud Cline (Mar 12, 2006)

You can't put Hardi over drywall. (Well I suppose you can) Why would you want to do that? The Hardi is not waterproof and will wick water through to the drywall over time.



> I had some reasoning for this, but it's probably faulty.


Yes I'm somewhat sure it is. After all of the above.

Okay Mike, Jaz, I'm out of this one. Take it boys.:thumbup:


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## Blondesense (Sep 23, 2008)

Scratch, have you seen Bud's blog? I think you might find it very helpful.

http://www.diychatroom.com/blogs/confused-about-constructing-shower-walls-152/


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## Maintenance 6 (Feb 26, 2008)

OK. you've got some folks confused. Here is what I think. Do the whole bathroom in moisture resistant drywall. It's a damp area prone to growing mold. MMR board is cheap insurance. Put the 5" piece at the bottom where it is mostly out of sight anyway behind a vanity, tub and toilet. Use Schluter Kerdi membrane in the shower area. Tile over it and forget about it.


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## fromscratch (May 23, 2011)

Thanks for the link to the blog post. I'm getting there.


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## Gary in WA (Mar 11, 2009)

http://publicecodes.citation.com/icod/irc/2009/icod_irc_2009_7_sec002_par013.htm

Gary


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