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-   -   Boring questions but I need the help. Please. (https://www.johnbridge.com/vbulletin/showthread.php?t=28973)

woodguy 11-07-2005 05:26 AM

Boring questions but I need the help. Please.
Hi All,

I'm new here so please be gentle.

I'm re-doing my bathroom and I've got a couple of questions that I'm confused about.

1: do I need to place a vapour barrier between the wonder board and the studs behind it in the tub/shower area and if so, can I use 6mm poly instead of roofing paper?

2: I've installed 5/8" exterior grade plywood over top of the original 5/8" flooring with screws every 6”-8", creating a sub floor of 1 ¼”, is this an acceptable practice for laying 12”x12” floor tiles?

3: I plan on using green board for the ceiling of the tub area, (I plan on painting it) can you see any problem with this?

As a frequent user of woodworking forums I know what it's like to see posts like this one...........................pretty boring stuff for you guys I suspect.

Any help would be greatly appreciated as I'm new at this game.


Davestone 11-07-2005 05:35 AM

Ho hum...yawn yawn... :wave: No way,Gord,we like the easy questions,i can't believe no-one latched onto it.1...yes...2..yes,if you've checked your floor joists on the deflecto above,on this page.....3 no,no problem.... :D

woodguy 11-07-2005 05:47 AM

Hi Davestone,

I've checked the Deflectolator and it tells me that things should be just fine. (that thing is cool)

I trully hope that you folks don't mind me posting these type of questions,( I'll have several more as I go along) I promise pictures when finished.


jgleason 11-07-2005 05:51 AM

Hi Gord,

One thing to keep in mind with greenboard on the ceiling - I believe the requirement is for it to be supported 12" on center instead of the usual 16"oc.

John Bridge 11-07-2005 05:59 AM

Welcome aboard, Gord. :)

Quit asking those boring questions, will ya? :D

In practice, greenboard get nailed over 16 in. centers routinely without problems.

bbcamp 11-07-2005 07:06 AM

OOH-OOH, Can I get a boring question, too? :yipee:

cx 11-07-2005 07:50 AM

No, Bob, you're still in charge of boring answers. Go sit down. :noid:

Welcome, Gord. :)

On the boring ceiling board, listen to Joe Gleason, not John Bridge. :mad:

There are times I really don't know why we let JB participate in these forums. :rolleyes:

Oh, wait......... It's his website, ain't it? :D

silverfox 11-07-2005 08:22 AM

You mentioned the 5/8" exterior ply over the old 5/8" ply...I don't know if you realize that you still need to use a CBU over that to install your tile. Or, if you have height problems, you could use a decoupling membrane like Ditra.

woodguy 11-07-2005 08:28 AM

Hi All,

Well if you like boring questions, here's another.

Removing the drywall in the bathroom I was struck by the fact that when the house was first built (typical 20 year old subdivision home), the builder used green board in the tub area and regular drywall everywhere else.

Now the strange part, most of the green board was ruined but the regular drywall everywhere else showed no signs of moisture damage or degrade.

So, here’s the question…………. would using regular 1/2" drywall ( I have it on hand now) everywhere but the tub area (I’m using wonder board there) be the thing to do?

I've seen others use green board everywhere in a typical 8'X6' bathroom and I’ve also seen others use regular drywall everywhere in the bathroom except the tub area. I do plan on installing a 140 CFM bathroom fan.

Regards and many thanks.

woodguy 11-07-2005 08:34 AM

Hi Silverfox,

I was told (yeah right), that I could go ahead and just use the plywood as a base for the tile. I'm thinking that CBU is a cement based product?

With a floor space of roughly 4'X6' to be tiled, won’t the plywood be enough?

If I need to install Ditra, then that's what I'll do. I'm the type of guy that wants to do it right the first time and I'm wide open to the ideas and experience of the people who know way more about this than I do.

Once again, many thanks for helping out a novice.


LazyPup 11-07-2005 12:15 PM

The plumbing codes require Greenboard on all bathroom walls except the shower enclosure.
You may not install moisture barrier behind greenboard.

The shower enclosure is to be backerboard until the wall is 72" above the finished drain elevation.

You Must install a moisture barrier behind backerboard. This may be building paper, tar paper or 6mil plastic.

Greenboard MAY NOT be installed on the ceiling if the framing is greater than 12" on center. (You may install firring strips 12"OC perpendicular to the framing, then attach the greenboard to the firring strips.)

woodguy 11-07-2005 01:05 PM

Hi LazyPup,

I don't know where you are in the world but I'm in Ontario Canada and I found the opposite to what you've said and I’m not surprised.

On the exterior wall of my bathroom, the wall was covered with green board and behind the green board was a six mil poly vapour barrier.

Everywhere else in the bathroom was regular 1/2" drywall including the ceiling.

Believe me when I tell you that I'm not doubting what you are saying and with no visible signs of the regular drywall deteriorating (after 20 years of use), I suspect that I'll go with my original plan.

I wonder why you can't put a vapour barrier behind green board, that one has me scratching my head.

Many, many thanks for all your help.


bbcamp 11-07-2005 02:21 PM

Gord, there is an approved method for installing tile on double plywood floors, but everything has to be done just right for it to work. A lot of pros do it, and a lot of pros get call-backs, too. Backerboard or Ditra installations are much easier for DITers to get right the first time.

woodguy 11-07-2005 02:44 PM

Hi Bob,

Thanks for taking the time to respond, you don't know how much of a help you guys have been so far, I hope I’m not pushing my luck.

I won't take any chances with this job; I don't want to ever do it again. I will gladly install the Ditra. I'm in a whole different world here and very unfamiliar. I'm just so happy that so many have offered up their help.

Normally I'm doing this kinda stuff..................

http://img.photobucket.com/albums/v1...ee_Table_1.jpg http://img.photobucket.com/albums/v191/gordgraff/1b.jpg

bbcamp 11-07-2005 02:48 PM

Like the coffee table. Gonna have to let the hall table and wall art soak in a little...;)

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