cement board tile backer over drywall?

[John Arnold]

Inspected a "rehab" today where there were access panels to two tile showers and a tub/shower. I hoped to find cement board as the backer for the tiles, but saw drywall instead.
My question is: is it common to install the cement board over drywall, so that you would only see the drywall when viewing from the other side of the wall?
In the photo you can see the rubber liner for the shower, and the drywall inside of it, which doesn't make much sense to me, even if there is cement board on the other side of the drywall.

28500

[Garry Sorrells]

Green Board with tile, but not just reg drywall. Though it is done in rehabs as a cheaper material. Will last for a while so long as no moisture gets to the drywall. A tile and run job. Or a drive by tiling....:p

[John Arnold]

Green Board with tile, but not just reg drywall. Though it is done in rehabs as a cheaper material. Will last for a while so long as no moisture gets to the drywall. A tile and run job. Or a drive by tiling....:p

Thanks Garry.
What I'm trying to figure out is - Do I assume there is no cement board between the tile and the drywall that I can see, or is it common to put the cement board over drywall?

[Mike Lamb]

Thanks Garry.
What I'm trying to figure out is - Do I assume there is no cement board between the tile and the drywall that I can see, or is it common to put the cement board over drywall?

It's not common. I'd assume no cementitious substrate and would say so. This is an old reference.

ANSI A108, A118, & A136 — 1999 American National Standard for Installation of Ceramic Tile AN-2.4.1 Some backing materials are subject to deterioration when subjected to moisture. When a tile installation is subjected to frequent wetting, backing materials of concrete, portland cement mortar, cementitious backer units, or masonry are recommended.

Garry is right. It is a drive-by tile job.

[John Arnold]

It's not common. I'd assume no cementitious substrate and would say so. This is an old reference.

ANSI A108, A118, & A136 — 1999 American National Standard for Installation of Ceramic Tile AN-2.4.1 Some backing materials are subject to deterioration when subjected to moisture. When a tile installation is subjected to frequent wetting, backing materials of concrete, portland cement mortar, cementitious backer units, or masonry are recommended.

Garry is right. It is a drive-by tile job.

Mike, Thanks. The more I look at install instructions for tile showers, the more I agree that there's probably no cement board there. I'm sure it's a complete coincidence that no permits were obtained for this "rehab"...

[Jerry Peck]

Green Board with tile, ...

Nope, green board is not for use behind tile in wet or damp areas such as showers or around tubs with showers; green board is for use behind tile in dry areas such as wall areas outside the shower area.


... but not just reg drywall.

I agree on that part - no drywall behind the cement board as then the cement board will simply be attached to, or through, a sponge and will not stay in place, this will cause all kinds of problems you would not even want to consider.

[Jim Robinson]

Kerdi is designed to be installed directly onto gypsum board. I've done three showers with it so far, and it seems like a good product. They love it over at John Bridge, so I thought I'd try it out. I think it is approved in PA, but it depends on what codes are in use.

Schluter-KERDI - Schluter-Systems (http://www.schluter.com/8_1_kerdi.aspx)

It's not necessary to use the rubber liner with it, but it probably wouldn't hurt anything to use a conventional base with the Kerdi system.

[Dom D'Agostino]

You can always pop the trim ring from the shower valve to see the cross-section of the wall.

Did they use a bull-nose or mud cap on the edges?

[John Arnold]

You can always pop the trim ring from the shower valve to see the cross-section of the wall.

Did they use a bull-nose or mud cap on the edges?

The top edge was finished with grout, if that's what you mean by mud cap.

[Steven Turetsky]

Mold loves cellulose and is colorblind.

[Jerry Peck]

Kerdi is designed to be installed directly onto gypsum board.

It is?

While I did not click through and read each of the available information links, I clicked on and looked as several of then, and not even a single one mentioned anything about installing on gypsum board.

Then, of course, there is the gypsum board manufacturer's who stated NOT to use gypsum board in those areas ... :confused:

- - - Updated - - -


Mold loves cellulose and is colorblind.

Steven,

I like that! Very good and simple way to put it. Cool.

Green ... board (MR board)

Blue ... board (plasterboard)

Gray ... board (regular drywall)

[Mark Hagenlock]

Click on Jim's KERDI link. Then check out the installation manual, page 5.... Just because you can doesn't always meen you should.

[Jerry Peck]

Click on Jim's KERDI link. Then check out the installation manual, page 5.... Just because you can doesn't always meen you should.


While I did not click through and read each of the available information links, I clicked on and looked as several of then, and not even a single one mentioned anything about installing on gypsum board.

Then, of course, there is the gypsum board manufacturer's who stated NOT to use gypsum board in those areas ... :confused:

Mark,

Yep, it is there ... as I said, I did not check all links ... but don't forget the last part of my post too ... "Then, of course, there is the gypsum board manufacturer's who stated NOT to use gypsum board in those areas ..." the manufacturers of the gypsum board would also need to give their thumbs up for their gypsum board to be used that way.

[Steven Turetsky]

Thanks Jerry. Paper is paper and that is what the mold likes.

In my bathroom every wall and ceiling is cement board, every joint is sealed with fiberglass mesh and thinset AND everything is coated with a moisture barrier. And while I may have overdone it (that is my way), I am happy I did it that way.

[Tabb Jensen]

Yes - you should have backer. But, Tile has been placed on drywall in bathrooms for a long time. It needs care to survive. It needs to be sealed, then resealed as needed, usually every 1-3 years. Water intrusion will destroy it.

[Bruce Lightfoot]

Yes - you should have backer. But, Tile has been placed on drywall in bathrooms for a long time. It needs care to survive. It needs to be sealed, then resealed as needed, usually every 1-3 years. Water intrusion will destroy it.

I'm not an HI, just a nosy neighbor on this occasion. I recently saw a situation where a tub spout had been hit hard and popped off a couple of tiles. Backer was 1970's era drywall, a nice bright black where it had not just fallen away, and some surface rotting of the 2x's as well. The handyman's fix was a wrench to re-bend the pipe (leaving a kink in the copper) and a bit of silicone to hold the broken tiles in place. He said he would recommend they install a tub liner when the bottom of the cast iron tub rusted through in a couple of years. Glad I was not the owner!

[Peter Louis]

I do not think any builder would put cement board on dry wall at shower closure.

[Jerry Peck]

I do not think any builder would put cement board on dry wall at shower closure.

I can't imagine why one would even consider doing that?? :confused:

[Mike Clarke]

Did not see or overlooked in the thread, was this a tiled shower or full fiberglass enclosed, etc ?
If full fiberglass, or if using panels not as bad but if tiled and not using other membrane then would be bad.
I still see many continue to use drywall with showers even when using tile, Using Kerdi may be different, just the way many did many years ago and their practice never changed or the way they taught their son taking over the business, etc. Always the way they have done it for forty years and do not want to change.

[John Arnold]

Did not see or overlooked in the thread, was this a tiled shower or full fiberglass enclosed, etc ?...

Tile.

[Nick Ostrowski]

I tell people it doesn't matter if greenboard or straight-up drywall was installed. They will both become damaged, moldy, and spongy if they get wet over and over. I think the only thing you could do John is a look around a cutout/penetration for the tub/shower fixture pipes and see if there is any cement board there. Other than that, I think it's just a guess.

[Jerry Peck]

I tell people it doesn't matter if greenboard or straight-up drywall was installed. They will both become damaged, moldy, and spongy if they get wet over and over. I think the only thing you could do ...

... is change that into a positive and explain to the buyers that ... :D ... the get to remodel and re-tile the shower every 5-10 years or so, no hard decisions to make as to 'should we or shouldn't we'; that will become 'we need to because the tile is coming loose'.

[H.G. Watson, Sr.]

I can't imagine why one would even consider doing that?? :confused:I can, circumstance when specifically required.When a bath/shower is installed upon a common separation wall, such as in a multi-family occupancy, or more often in a row-type townhome which has utilized the specifically prescribed alternative to a masonry "fire wall", i.e. the now prescribed separation and formerly identified UL assemblies for one-hour separations, especially for those "party walls".When the code prescribes a covering to same "or equallivent" to gypsum wall board (equal such as plaster, etc.) the fibercement board is not equallivent in ALL the characteristics necessary when "fire testing" performance of the party wall/firewall one-hour/two-hour fire resistive assembly requiring two-each 5/8" gypsum wall board independantly taped and mudded, staggered on each side of the studding of the wall assembly. I know of NO such vintage or current assembly which allows for the replacement of required gyp board with durarock or similar as a tested (by fire) assembly modification/substitution esp. not repairing a vintage (no longer current code compliant such as insultion or studding) assembly. When Those two 5/8" gypsum board, staggered on studs, independantly taped & mudded on each side of the stud wall is specified - you may not replace one layer (or both) with durarock or similar, unless the entire modification is approved as a part of a listed/tested approved assembly (the entirety of the specification and build of the entire separation wall).To maintain the specification of the (dated edition) of the former assembly - apply to and upon but not a replacement TESTED to the ASSEMBLY which was specified and approved at original construction.

[Jerry Peck]

I can, circumstance when specifically required.When a bath/shower is installed upon a common separation wall, such as in a multi-family occupancy, or more often in a row-type townhome which has utilized the specifically prescribed alternative to a masonry "fire wall", i.e. the now prescribed separation and formerly identified UL assemblies for one-hour separations, especially for those "party walls".When the code prescribes a covering to same "or equallivent" to gypsum wall board (equal such as plaster, etc.) the fibercement board is not equallivent in ALL the characteristics necessary when "fire testing" performance of the party wall/firewall one-hour/two-hour fire resistive assembly requiring two-each 5/8" gypsum wall board independantly taped and mudded, staggered on each side of the studding of the wall assembly. I know of NO such vintage or current assembly which allows for the replacement of required gyp board with durarock or similar as a tested (by fire) assembly modification/substitution esp. not repairing a vintage (no longer current code compliant such as insultion or studding) assembly. When Those two 5/8" gypsum board, staggered on studs, independantly taped & mudded on each side of the stud wall is specified - you may not replace one layer (or both) with durarock or similar, unless the entire modification is approved as a part of a listed/tested approved assembly (the entirety of the specification and build of the entire separation wall).To maintain the specification of the (dated edition) of the former assembly - apply to and upon but not a replacement TESTED to the ASSEMBLY which was specified and approved at original construction.

Nonetheless ... one does NOT want tile applied to the gypsum board used for the resistive barrier.

Therefore my statement/question stands - I cannot imagine why one would put cement-board on drywall ... the moisture will go through the cement-board and ruin the drywall ... I hope *you* would not want the gypsum board installed on a fire-resistive wall ruined by moisture from a shower - repairing that fire-resistive wall will be quite a task to do properly, and permits and inspections will be required, although whomever does the work will think permits and inspections are not required.

Yes, bathtub shower areas and shower stalls are frequently located next to fire-resistive walls because that reduces the plumbing cost, but it does not take much to offset that cost and relocated those tub and shower areas so they are not up against the fire-resistive walls.

Just poor planning on the architects part in my opinion. The thing that happens most of the time is that they forget to run the type x drywall down beyond the tub, leaving the under-tub area open to the inside of the fire-resistive wall.

If the tub and shower areas are to be against that fire-resistive wall, install the type x drywall as required, install furring strips, then install the cement-board, making sure to properly fire-block as needed. Problem solved - except that they now lost 3/4" of space in the condos/apartments along each side of that wall.

[don agel]

I do not think any builder would put cement board on dry wall at shower closure.

Believe it nor not caught 3 times in Raeford NC, and once in Wilmington NC this year alone. There are some builders who use sub-par sub contractors and in small townships the building inspection departments may be inadequate to non-existent. Raeford NC falls in Hoke County. That entire area has two building inspectors for the entire department who happen to ride together in the same vehicle. Can't imagine why I cringe every time I get a new construction in that county.

- - - Updated - - -


If the tub and shower areas are to be against that fire-resistive wall, install the type x drywall as required, install furring strips, then install the cement-board, making sure to properly fire-block as needed. Problem solved - except that they now lost 3/4" of space in the condos/apartments along each side of that wall.

:applouse: Too easy!

[Mark Reinmiller]

Kerdi is designed to be installed directly onto gypsum board. I've done three showers with it so far, and it seems like a good product. They love it over at John Bridge, so I thought I'd try it out. I think it is approved in PA, but it depends on what codes are in use.

Schluter-KERDI - Schluter-Systems (http://www.schluter.com/8_1_kerdi.aspx)

It's not necessary to use the rubber liner with it, but it probably wouldn't hurt anything to use a conventional base with the Kerdi system.

Note the hijack the thread, but...I planning a master bathroom renovation and just read about Kerdi last night (at John Bridge). It does sound like a good product. Did you use it with a mortar bed for the floor?

[Jim Robinson]

Yes. I followed the instructions from the John Bridge web site and the Kerdi instructions. I set the drain height first, then I constructed the sloped floor with the mortar mix. The Kerdi material is applied to the mortar floor and to the drain edges. It's been working great for 5 years or so now.

[Mark Reinmiller]

Yes. I followed the instructions from the John Bridge web site and the Kerdi instructions. I set the drain height first, then I constructed the sloped floor with the mortar mix. The Kerdi material is applied to the mortar floor and to the drain edges. It's been working great for 5 years or so now.

Thanks for the reply. I am debating between a mortar bed and the prefab bed they make.

[Jeff Zehnder]

Thanks for the reply. I am debating between a mortar bed and the prefab bed they make.

I know it has been stated but in the interest of brevity...the pan material and the drywall are both not installed according to the manufacturers standards and specifications!

[Mark Reinmiller]

I know it has been stated but in the interest of brevity...the pan material and the drywall are both not installed according to the manufacturers standards and specifications!

I'm not sure if you are responding to my questions, but I do not see any reason why a mortar pan or drywall backing do not meet the manufacturer's requirements. You can question whether you think the products are adequate for water resistance, but they are approved for that installation.