Greenboard/vapor barrier/etc questions

Hello all - this is my first post, been lurking for a week or two. Great site, lots of good info here!

Here is my dilemna: I'm getting ready to remodel my 72 sf bathroom. House was built 1945-ish. Right after Hurricane Katrina, I went and bought enough greenboard to completely cover the whole bathroom - I figured due to the small size of the bathroom, it would simplify and give me additional protection against moisture. (I bought it after Katrina figuring the price would skyrocket ) Now I've read a few things on here that make me wonder.

Anyways - I'm looking for suggestions on how to reinsulate and provide a vapor barrier, all while avoiding any mold issues. Unfaced batts with poly, kraft faced, or ? Bear in mind that in a couple years I want to reside the home, and when I do, I am hoping to put a tyvek type product, or 1/4" insulpink (taped seams) on before I side (most likely with vinyl or fibre cement). The bathroom does not currently have an exhaust fan, but I am adding one. It is my understanding that Tyvek allows moisture to escape - would it make sense to go with unfaced batts and tyvek on the interior instead of poly?

So - I would like to use the already bought and paid for greenboard - I know a suggestion would be to not use the green board throughout the room, I'm hoping to avoid that if possible.

Thanks in advance for any help!!

Rich

Why are you hesitant to use the green board? Some people were confused a while back when it was finally determined that green board should not be used as a tile backer in showers, but it is fine for the rest of the bathroom. If you are using it on ceilings, you should fasten it every 12" rather than 16, so you will likely have to use strapping. Though, I have seen plenty of greenboard on 16" oc joists with no sagging.

Putting the screws every 12" on the 16 o.c. joists or trusses should meet code. Not sure why strapping would be needed. But maybe I'm wrong I'm just an amateur.
People don't like the green stuff on the ceiling because the green stuff holds lots of moisture and could sag. The best solution is to try and keep it dry in the first place. Use good sealer and paint If you're really that worried you could put in more screws or paint both sides of the drywall with primer/sealer before installing.

As for your questions re: the vapor barrier, the idea is to prevent condensation. So in a place where it's dry and cold in the winter like here in Colorado you put it on the inside of the insulation toward the living space to keep the condensation off the insulation. But in a place that usually hot and humid with air conditioning you might be required to put the vapor barrier on the outside of the insulation. I think if you google insulation and vapor barrier you might find out where the different codes apply.

Greenboard is not as strong as regular drywall, so if used on a ceiling, it must be supported at 12" intervals rather than the 16" for regular drywall. As of the first of the year, greenboard is no longer in the national code, so it doesn't have much required uses. CBU is needed in shower/tub surrounds where you are tiling with a shower, and there normally isn't enough moisture in the rest of the bathroom to justify the stuff. If you have it, go for it, just don't use it in the shower.

jadnashua said:

Greenboard is not as strong as regular drywall, so if used on a ceiling, it must be supported at 12" intervals rather than the 16" for regular drywall. As of the first of the year, greenboard is no longer in the national code, so it doesn't have much required uses. CBU is needed in shower/tub surrounds where you are tiling with a shower, and there normally isn't enough moisture in the rest of the bathroom to justify the stuff. If you have it, go for it, just don't use it in the shower.

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I am going to use greenboard in my bathroom and cbu for where I am tiling in my shower..

My question is..

How do I deal with the small gap where the 2 materials meet?

A) Do I install them flush to each other exactly where the top of the top tile would end and then joint compound the seam?
B) Or do I run the cbu a bit higher than the top of the top tile and joint tape and paint.
C) Or do I run the cbu a bit lower than the top of the top tile and basically tile over the seam?
D) Or doesn't it matter!?

I'm going to head over to a tiling forum but wanted to see what you all thought as well.

Thanks,

Run the cbu slightly short, and then put up the tile. Use the alkaline resistant mesh tape on the seams and thinset. For a really neat finish line, paint the wall first, slightly past where the tile will go. It looks much nicer than any line you can paint after. Works for the first time only

jadnashua said:

Run the cbu slightly short, and then put up the tile. Use the alkaline resistant mesh tape on the seams and thinset. For a really neat finish line, paint the wall first, slightly past where the tile will go. It looks much nicer than any line you can paint after. Works for the first time only

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Sounds like a plan.

Alkaline resistant mesh tape? Never heard of it. Is that different than the normal mesh type one would use for drywall finishing?

I'm assuming one doesn't caulk the top tile.. the grout will suffice to keep water from getting behind the tile, correct?

That tape looks the same as fiberglass tape used for drywall, but it will hold up in the thinset, the drywall stuff won't. You should find it near the display of the cbu and screws.

At the top of the last tile on the wall, you would not normally expect water to get there in the first place. If it did, the drywall would have problems, too. The top tile only needs to be grouted, and you usually don't grout the edge, although I've seen it done. Usually, you need some sort of trim tile like a bullnose, so you don't have the unfinished edge showing. Several companies make metal and plastic trim pieces for tile. One that has a good assortment that you might like is from www.schluter.com . They also have some expansion joints that you can use in the corners and at the top edge of the tub so you don't need any caulk. If the tile is unglazed, through-body porcelain, you can have the edges rounded and polished if they don't have a trim piece. Check with a granite fabricator shop to see if they would do it for you.

Now that I talked to my wife, we do plan on using a bullnose at the top. I guess I am just wondering if that gets grouted or caulked or neither..

The joints on the sides and bottoms, usually not at the top; depends somewhat on how thick the thinset is, there usually isn't a gap there to grout. The grout ties the tiles together, protects the edges and corners, and seals things up (to a degree - at least for keeping crud from getting between the tile). Note, make sure to use a mortar (dry bagged) thinset, not a pseudo-thinset (mastic) in the wet areas. Real thinset is much cheaper and won't be affected by the moisture.

jadnashua said:

The joints on the sides and bottoms, usually not at the top; depends somewhat on how thick the thinset is, there usually isn't a gap there to grout. The grout ties the tiles together, protects the edges and corners, and seals things up (to a degree - at least for keeping crud from getting between the tile). Note, make sure to use a mortar (dry bagged) thinset, not a pseudo-thinset (mastic) in the wet areas. Real thinset is much cheaper and won't be affected by the moisture.

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Why not a mastic? We're tiling our shower area. My wife went to get our tile and supplies from the tile house and they recomended and sold us Durabond D-1001 Mastic.

What is the detriment of using this? I would assume a tile house would know their stuff. Why would they recomend this?

Read the fine print on the stuff. Mastic stays soft in the bucket for a very long time...it needs to dry out to become stable. Grout is NOT waterproof, moisture will constantly go through it, especially in the lower parts of the shower. The stuff will re-emulsify in the shower, and turn to mush.

Real thinset is much cheaper, and when it cures, is unaffected by moisture. It will last for an eon. Why risk it? Mastic is fine for areas that don't get wet, not in a shower, though. Get some other thoughts on the www.johnbridge.com "Tile Your World" website. The guys ast HD will tell you to use mastic, too. Doesn't make it right or make it work in the long term.

jadnashua said:

Read the fine print on the stuff. Mastic stays soft in the bucket for a very long time...it needs to dry out to become stable. Grout is NOT waterproof, moisture will constantly go through it, especially in the lower parts of the shower. The stuff will re-emulsify in the shower, and turn to mush.

Real thinset is much cheaper, and when it cures, is unaffected by moisture. It will last for an eon. Why risk it? Mastic is fine for areas that don't get wet, not in a shower, though. Get some other thoughts on the www.johnbridge.com "Tile Your World" website. The guys ast HD will tell you to use mastic, too. Doesn't make it right or make it work in the long term.

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I went over to John Bridge last night (and posted my 1st message) and found out exactly what you all are saying. It was amazing how definitive all the answers were... DON'T USE MASTIC WHERE WET... I am convinced.

It makes me really question why on earth the tile place (or HD folks) would recommend it. Where are they getting their info? I'm actually going to go back and find out when I return the mastic.

jadnashua, did you see my post on john bridge? It's similar to the one I posted on this forum but I added some questions. Can you take a read over there and post a response?

Thanks!!

I'm confused and *must have missed something*.Later this year I'm going to tile a small bath/shower which currently has cheap vinyl/plastic protecting the wall now.

..I was going to have someone nail up some wonderboard and do the tiling myself.

Am I hearing that a layer of thinset on the drywall is all thats needed...with plastic.......??

Could I tile directly onto this thin plastic?

Vapor barrier, cbu (cement board, Wonderboard is one brand), then tile. If you want, take out the current vinal and drywall, and replace with 1/2" cbu, then you won't have as much buildup. You still need the vapor barrier between the cbu and the wall behind it. Run the vapor barrier over the lip of the pan.

I see. I need to have someone pull out the old drywall-replace with

1.vapor barrier
2.1/2 inch wonderboard

The wonderboard *is* the dry wall essentially. then tile away.....


which is a great idea as I NEED as much space as possible.

The best place for tiling info is www.johnbridge.com

I've been to John Bridge in the past and just did again-thanks. I now have a pretty good grip on what needs to be done-thank you.

I have a good old boy neighbor who appreciates it whenever I have some work for him and his carpentry skills are pretty decent. My question to you is...is this something that isnt critical that a pro do it. How serious could mistakes be..?

It's not in my budget to pay a professional 3-500 bucks to nail up plywood and wonderboard and prep the walls....if I can help it.
This small bathroom remodel has already cost me nearly a couple grand-and I haven't even *started* on the shower yet.

I'm good with the actual mosaic work myself being an "art guy" so that will save me a lot right there.
I want to spend my budget on exotic tiles and design materials if possible.

It appears I will have to use the second shower in the interim which is as small as a cruise ship shower. The previous owner of this house bought the cheapest possible furnishings available thruout. I'm literally replacing everything from door hinges to shower and so on...

If you are handy at all, you should be able to do it. On John's site, there is a pretty detailed instruction in the 'liberry' link in the menu bar at the top of the forum. Read that, then ask questions. Lot's of people go through there and DIY with good results.

After being convinced here and on johnbridge not to use mastic, I asked my wife to return the mastic that the tile place sold her. Sure they took it back, but I just found out they charged a 30%!! restocking fee. What a bunch of thieves. I would say worse but I don't want to get kicked off this forum.

I am really bitter. They convinced her mastic was OK to use in the shower area, then charged 30% when we realized it wasn't true and wanted to take it back.

I wish I had read all this before I sent her to the store in the first place. Lesson learned.