Replacing tile - need new cement board?

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Old 12-30-14, 10:56 AM
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Replacing tile - need new cement board?

I am doing a reno of a guest bathroom where the shower/tub rarely gets used. I removed the tile from the wall in the tub area. I am wondering if I need to replace the cement board.

I attached a picture. It is generally in good shape. I don't know if the existing thinset is a problem. It is pretty thin (the old tiles were 4x4 in).

Problems I see with not replacing the cement board are:

1) old thinset on wall
2) The seems were not taped
3) They used drywall screws rather than the self healing type

I plan on using large format tile as the replacement (at least 12x12). I am trying to keep this reno as simple as possible. I know cement board is not that hard to replace, but would rather not unless it will be a big problem later.

I should add that I am not replacing the tub.

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Old 12-30-14, 11:02 AM
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Also looks like it was not waterproofed before tiling.
Should have had a product like Red Guard or Hydoban before the tile.
As long as there's no high places and the seams get taped it should work.
 
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Old 12-30-14, 11:21 AM
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Can I tape though over the existing mastic? There is no way I will ever get that off and so the tape would be on the mastic, not the actual cement board.
 
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Old 12-30-14, 12:32 PM
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So it's mastic and not thinset as you first thought? Sure looks like mastic.

Being that it's a tub surround I would probably work with it, a shower stall would be a different story. But, can you get that tub edge clean? Does the wall clear the tub flange so the tiles can be set plumb?

You need to get any high spots off and make sure the walls are flat in all directions. Use a 4-6 ft. straight edge. You can cut off mastic using a wallpaper scraper which has a razor cutting edge. I guess you're gonna have to use mastic again instead of the preferred thinset.

Jaz
 
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Old 12-30-14, 01:12 PM
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I guess you're gonna have to use mastic again...
:NO NO NO: Jaz - Not too distant past, you zipped me for suggesting the replacement of one 6x6 floor tile in a non-wet location and I suggesting mastic.

I would chip away as much of the mastic as possible. I recently finished a bathroom that used mastic around a tub surround. The cement board was sound, only had to chip off the mastic. Tedious but a necessity. Use a 3" stiff putty knife as a wide blade chisel and chip across the trowel marks. It will release, just takes some time.

Leave the drywall screws and set correct cement board screws next to them to secure. Tape the seams with appropriate cement board fiber tape and also skim over those areas where you damaged the mesh tape embedded in the cement board and inset new fiber mesh tape.

Mastic is not rated for wet area, be it tub or shower. 95% of tub situations are used as showers so in my book there is no distinction.
 
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Old 12-30-14, 01:47 PM
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It might be easier replacing the cement board. There is a lot of fiberglass mesh from the cement board visible and any scraping will be very difficult.
 
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Old 12-30-14, 03:42 PM
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Originally Posted by czizzi
Jaz - Not too distant past, you zipped me for suggesting the replacement of one 6x6 floor tile in a non-wet location and I suggesting mastic.
I don't recall that incident, but it makes sense that I would say that. The reason is obvious to me. Mastic stays soft for a long time and shouldn't be used on floors.

I'd recommend thinset for this thread too, if there wasn't mastic on the wall already. Although it might still work, no sense taking a chance.

Mastic is not rated for wet area, be it tub or shower. 95% of tub situations are used as showers so in my book there is no distinction.
Actually for type 1 & even type 2 mastics that's not true. They can be used in "intermittent wet" areas, just not on wet floor applications. There's a big difference between tub surrounds and stall showers. Most of the damage in showers happens to the floor, curb and the 1st foot up. Tub surrounds are not as prone to failure , even when not done to high standards. Plus Michael already said it's a guest bathroom that rarely gets used and wants to keep it as simple a he can and there's no evidence of mastic failure in the old job.

Michael, your choice about starting over. You can certainly do that. Did that tub edge clean up well?

Jaz
 
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Old 12-30-14, 03:59 PM
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Michael, your choice about starting over. You can certainly do that. Did that tub edge clean up well?
Yes, the tub is fine.

Are you saying you think it would be okay if I stick with mastic for the new tile?

I have never used mastic before and was hoping to use thin set just because it is what I am used to.

There are divots in some places where the cement board came off on the back of the tile. I would have to fill those in if I didn't replace the cement board. That and dealing with this old mastic is making me think new cement board might be the best option as much as I was hoping to avoid that.
 
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Old 12-30-14, 04:07 PM
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In August, I demo'd a shower that used mastic. To get the tiles off the cement board, I used one hand and a light touch - the tiles literally fell off the wall. I actually used one hand to remove tile, and the other to video tape so I could show the owners when they came home. The mastic was still wet 48 up the wall. All the fasteners were rusted and I did not feel comfortable using what was there. I pulled all the cement board from the wet location and replaced.

Here was that demo - http://vid282.photobucket.com/albums/kk246/czizzi/IMG_0820_zpswsddbqiy.mp4
 

Last edited by czizzi; 12-30-14 at 05:27 PM. Reason: Add Video Link
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Old 12-30-14, 05:29 PM
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Half the battle for us is convincing people to do a little more work than they expected so the job can be done using best-practice. You are willing to do just that. So go ahead, you won't be disappointed. You'll save yourself the trouble of scraping mastic bumps and while you're at it you can check and fix any out of plane studs. Since you're going with larger tiles the walls will need to be very flat.

Good example czizzi refers too. The same thing has happened with thinset when not done right. I've seen tiles set with thinset buckled out away from the wall an inch or two held together only by the grout. Remove one tile and down they come. I removed 3 bathroom floors in the same house done with mud base and thinset using only a small flex putty knife. The homeowner was amazed as he video'd the process.

So this time be sure to also tape the seams and apply a surface waterproofing too.

Jaz
 
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