# Moisture barrier in bathroom



## secutanudu (Mar 15, 2009)

I am remodeling my bathroom down to the studs. I have seen on home shows that they put plastic sheeeting up on the studs (after insulating) before drywalling. Is this necessary? If so, is there a proper way to install it to make it the most effective? Do I put it on the ceiling?

My original plan was to use moisture/mold resistant drywall and faced insulation on the outside wall. 

Also, I plan to use insulation on the inside walls also for (minimal, I know) sound proofing. Should this be faced or unfaced?

I will be using a schluter kerdi shower system, so I am not worried about vapor protection inside the shower. I am thinking more of the drywalled areas and the ceiling.

Thanks.


----------



## Nostco (Apr 8, 2010)

Alright, that plastic you saw on TV is called a vapour barrier. Typically 6mm poly. You only use it where one side is cold and one side is warm...exterior walls (vs. INTERIOR walls which are not touching the OUTSIDE of your house).

If you use that mold "resistant" drywall, it usually comes with a backer that acts like a vapour barrier. If you use that drywall on top of a vapour barriered exterior wall you create a double vapour barrier (BAD).

I hope you're using cement board or another approved backer for the shower/tub surround and not the mold resistant drywall. Check local codes, even if code for your area says it is ok...still think twice.

If you're using the insulation with a paper face, that usually acts as the vapour barrier and you don't put poly on top of that. Once again, double vapour barrier bad. For interior walls, if you want to reduce sound use soundproof insulation. Vapour barrier has to be continuous and air tight, which means tuck tape, staples, caulk, overlapped seams, proper electrical boxes.

Insulation and electrical - check local codes and make sure you're using approved boxes in insulated walls...insulation must be 6-12" away from naked boxes OR used approved boxes with vapour barrier.


----------



## secutanudu (Mar 15, 2009)

Thanks for the reply. I will be using concrete board for the shower, mold resistant drywall for the rest. The shower is not on an outside wall. There will be no electrical on the outside wall either.

So, is it bad to use mold-resistant drywall AND paper-backed insulation? That would be a double vapor barrier, and bad, yes? My initial thought was to use unfaced insulation on the outside wall, covered by plastic, then the mold-resistant drywall. This would also be a double vapor barrier, right?

I don't know where to find soundproofing insulation, i figured just throwing some unfaced fiberglass would be cheap and better than nothing. I'll cover that up with mold-resistant drywall (no additional vapor barrier). I imagine sound barrier insulation is more expensive than fiberglass? For interior


----------



## Nostco (Apr 8, 2010)

secutanudu said:


> Thanks for the reply. I will be using concrete board for the shower, mold resistant drywall for the rest. The shower is not on an outside wall. There will be no electrical on the outside wall either.
> 
> So, is it bad to use mold-resistant drywall AND paper-backed insulation? That would be a double vapor barrier, and bad, yes? My initial thought was to use unfaced insulation on the outside wall, covered by plastic, then the mold-resistant drywall. This would also be a double vapor barrier, right?
> 
> I don't know where to find soundproofing insulation, i figured just throwing some unfaced fiberglass would be cheap and better than nothing. I'll cover that up with mold-resistant drywall (no additional vapor barrier). I imagine sound barrier insulation is more expensive than fiberglass? For interior


I believe HUMIDEX by CGC (blue stuff) does not come with the vapour barrier black backing. The green stuff "Water resistant" panels by CGC, Do have the black backer paper. Now if you use that, with a vapour barrier (poly) then you are creating a trap for moisture which you don't want. Now, CGC will tell you don't use this product (the green stuff) with a vapour barrier IF you're going to tile over the drywall. Because you create a trap for moisture, BUT...I say (and this is coming from experience so take it or leave it) Don't use it with a vapour barrier regardless of whether you're going to tile over it or not.

Just use the Blue Humidex and you'll be fine.

The sound proof material (Like "Safe and Sound") is not expensive and can be bought at any Home Depot, Lowes, etc. It does come in a package that covers X amount of wall sq/ft...so if it's just a small area it's not worth it...it's about the same price as the regular batts but is really just fire/noise protection and doesn't give you a good R rating so only use it in interior spaces. Hope that helps.:thumbup:


----------



## secutanudu (Mar 15, 2009)

Thanks for your help with this.

The drywall that I bought is from Lowe's, and it's purple, not green. It is mold, mildew & mosture resistant. Here it is:

http://www.lowes.com/pd_121507-272-...151&Ntk=i_products&ddkey=http:CategoryDisplay

It's purple on both sides, no black. Does this count as a vapor barrier? I'd feel better if I could use plastic behind it on the exterior wall. I will not be tiling on any drywall, and this will all be primed/painted with Zinsser kitchen & bath products.


----------



## secutanudu (Mar 15, 2009)

So I looked at the back of that purple drywall...it in fact IS very dark gray (not purple like the front). Does this count as a moisture barrier? Should I still used faced insulation or unfaced and cover with plastic sheeting?

Or should I use unfaced insulation with this drywall on top of it and nothing else?

Thanks.


----------



## ccarlisle (Jul 2, 2008)

You said that you'll be using the Kerdi shower system...what in terms of mositure do you think the effect will be if you use that? 

Why do yoy think Schluter say you can use regular drywall, if moisture was a problem?

I think _that_ is where you start your examination of moisture problems in a shower in Albany NY.


----------



## secutanudu (Mar 15, 2009)

I am not really concerned with the shower, as stated it is on an interior wall and will be lined with Kerdi. I am more concerned with my exterior wall, which will not have the shower.


----------



## Nostco (Apr 8, 2010)

secutanudu said:


> So I looked at the back of that purple drywall...it in fact IS very dark gray (not purple like the front). Does this count as a moisture barrier? Should I still used faced insulation or unfaced and cover with plastic sheeting?
> 
> Or should I use unfaced insulation with this drywall on top of it and nothing else?
> 
> Thanks.


The manufacturer says it's ok to use that drywall, with a layer of vapour barrier (poly or paper face insulation)...so long as you don't tile over it. Now that is what the manufacturer says for the CGC products, I don't know if the purple stuff is the same.

You need a vapour barrier, the drywall backer doesn't count as one.

I prefer regular batts with 6mm poly.
I'm not a fan of the paper faced insulation.
I try to use 2lb poly spray whenever/wherever I can (sometimes the area is too small and not worth it).

I know, it gets a little confusing at first. :wink:

So for your sake, if you are willing to trust the manufacturer's specs:
-Regular batt insulation
-6mm poly (properly installed).
-Mold resistant/water resistant drywall (green, blue, purple-check that one)
-Don't tile over it (you said you wouldn't)
-You have an Uncle and his name is Bob :wink:


----------



## secutanudu (Mar 15, 2009)

Ok, this is all starting to make sense. I'll go with unfaced batts with 6mil plastic sheeting. I will caulk/tyvek tape the seams - that good.

The only thing I am wondering about is this Uncle Bob. I need to have a serious talk with my parents about this unknown uncle!


----------

