RE: CBU single layer/Construction adhesive [Archive] - Ceramic Tile Advice Forums - John Bridge Ceramic Tile


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01-20-2003, 10:00 AM
Well, I chickened out and decided to hire a tile guy. As a practical matter, I've been building this bathroom for over 5 years and my wife is gonna beat me silly if don't finish it soon. The drywall is up and electrical finished. Years ago, I purchased a Kohler Symbio pan. It cost some bucks and my wife wouldn't let me scrap it for a puored pan. Anyway here's the question. My tile guy is going to put up cbu using 4X8 sheets for less joints. He mentioned using construction adhesive as well as screws. He also asked me about finishing the shower area with greenboard prior to the cbu. Unfortunately there is no room for greenboard. Just room for CBU. The pan and drain is in. If I sheet the shower area studs with roofing felt prior to the CBU as I've seen it done in pictures, how's this guy gonna use construction adhesive over the felt paper. Is the felt paper a necessity, r can the cbu go directly over the studs? Help....Thank you...

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01-20-2003, 10:12 AM
I would certainly not worry about using a construction adhesive with your CBU.Either the felt or 6 mil poly for a vapor barrier can be attached directly to your studs.I use a hammer tacker to staple the material to the studs.
Why does your tileman feel a need to use adhesive?
He can either screw the product using special screws by durock or he can Nail the CBU with dipped galvanized roofing nails.I generally use the nails.Adhesive is not neccesary.After the CBU is up tape all carners and seams with duroc tape and skim with thinset. Have fun!!

John Bridge
01-20-2003, 06:17 PM
Hi Casman, Welcome. :)

Hey, this tile guy you have must be massive. I have a hard time lifting and manipulating the 3x5 sheets of CBU. ;)

01-20-2003, 06:23 PM
Bud said he uses adhesive with cbu's also.

01-20-2003, 06:41 PM
Jeremy, Bud doesnt use a vapor barrier..
If you ever tear out a nailed CBU job, you will understand that there is no need for an adhesive.It does not come out easy :)

01-20-2003, 09:57 PM
Ditto John !!!

I've never seen 4x8' sheets of CBU. heck, the 3x5' @ 1/2" thick are bad enough.

I would like to know where to find the 4x8' sheets though


Bill Vincent
01-20-2003, 10:57 PM
Jason-- they're usually special order from a lumber yard-- as are 5'x10' sheets

01-21-2003, 08:48 AM
Well then, do I even need the felt or Poly vapor barrier, I know this is a can of worms but it'd be nice to know! The 2 shower walls are interior walls. Also, should I insulate these walls with fiberglass or would that be unnecessary except for possible sound deadening? If I use the felt then it would seem that const adhesive would be useless. I guess I should have asked more questions but is it usual for a tile pro not to use felt paper or is it because the walls are interior? Your help is appreciated and with my questions it is understandable why this project is taking me so long...

01-21-2003, 01:24 PM
Now you went and did it, you found an area where there is a little contension. Most agree to use a vapor barrier some do not.All i know is in all the tear outs i have done there is less structural replacement on showers that HAD avapor barrier.As far as insulation goes,it is only a sound thing on interior walls yes, but its alot easier to put in now than later. Also, you may want to consider putting blocking in now in the event you want handicap bars installed down the road. A few chunks of 2x12 put in now will save headaches later.(just a lil tip ) :)

Bill Vincent
01-21-2003, 05:35 PM
The vapor barrier is required for a reason. Short term, usually you can't see any difference between a shower with, or a shower without vapor barriers. A contractor I used to work for didn't believe in them, and as a result I was never given the time to put any in while in his employ, so I'm waiting. I expect in another year or two, alot of the showers I put in for him will be coming back down. The damage is done over a longer period of time. As moisture permiates the walls, being that it's a minimal amount, it does nothing but dampenthe wood to begin with, but the effects are cumulative, and after a few years, there's a distinct difference that can be readily seen. Without a vapor barrier, you'll see that the studs will turn black and start getting slimy, as they begin to deteriorate, and over time, if allowed to go on for too long, you'll see a total structural failure.

Use the vapor barrier.

John Bridge
01-21-2003, 08:50 PM
It's so cheap and takes so little time, it's foolish not to put the vapor barrier in (unless you intend to waterproof the surface of the substrate).