# Backerboard to Drywall Seam



## artinall (Aug 14, 2007)

Have a case of installed backerboard around a tub surround that was already tiled. But they left the unfinished backer extend about two inches on the sides into the drywall area. 

So to tape and skim the two surfaces - 20 min mix with mesh? Is okay over backer material?

Also, where the side backer walls meet the ceiling, how to treat the gap? Mesh'd be hard to use on the inner corner, and I hate to caulk ! 


BTW: searched this forum, thinking there was something about this...


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## AustinDB (Sep 11, 2006)

I've treated it like sheetrock and used mesh tape and 45 (I'm not fast enough to spread 20 and clean it up)


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## MarkJames (Nov 25, 2012)

Use paper tape or fibafuse. Mesh does nothing when it's all dry. (And the debate continues...) I would use 5 or 20 and get it all done.


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## Idothat (May 19, 2018)

Agree with other replies, tape and mud no problems .


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## artinall (Aug 14, 2007)

MarkJames said:


> Use paper tape or fibafuse. Mesh does nothing when it's all dry. (And the debate continues...) I would use 5 or 20 and get it all done.


 Didn't know if paper tape was alright over the backer... You are quicker than me, with that 5.

Whenever I apply backer/cement board, I end up just shy of the border so it's clean, no seams to deal with. So long as it's sealed.

- Does the backer need primed with the mud or 20 min?


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## MarkJames (Nov 25, 2012)

artinall said:


> Didn't know if paper tape was alright over the backer... You are faster than me, with that 5.
> 
> Whenever I apply backer/cement board, I end up just shy of the border so it's clean, no seams to deal with. So long as it's sealed.
> 
> - Does the backer need primed with the mud or 20 min?


Primer not necessary, but you might want to damp wipe any cement dust off. It doesn't have to be bone dry, either.

You can mix your setting compounds, so 5 and 20 will give you something in between.


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## artinall (Aug 14, 2007)

Believe it to be Hardiebacker but will have to confirm...


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## onmywayup (Aug 18, 2012)

Could also run another row of tile or bull nose to cover the seam? Or some complimentary mosaic tile?

Obviously the mud would be faster though


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## tjbnwi (Feb 24, 2009)

Use Kerdi band, bedded with mortar, covered with hot mud for finish.

Tom


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## artinall (Aug 14, 2007)

tjbnwi said:


> Use Kerdi band, bedded with mortar, covered with hot mud for finish.
> 
> Tom


 I like the looks of that, and lightweight. Next time I do!




onmywayup said:


> Could also run another row of tile or bull nose to cover the seam? Or some complimentary mosaic tile?
> 
> Obviously the mud would be faster though


 Nice thought but that would extend beyond the wall of the tub, at the base...and a window interferes.


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## Tom M (Jan 3, 2007)

tjbnwi said:


> Use Kerdi band, bedded with mortar, covered with hot mud for finish.
> 
> Tom


Do you plan your seam behind the bullnose tile then hot mud to the tile after its installed


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## tjbnwi (Feb 24, 2009)

Tom M said:


> Do you plan your seam behind the bullnose tile then hot mud to the tile after its installed


Normally end up doing 1 coat of hot mud about 1/4" into the tile area, prior to setting the tile. 

Tom


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## tjbnwi (Feb 24, 2009)

Two different situations. The blueish is Noble brand.

On the straight wall just the liner was used, no need for a band. It covers the seam by 4-5". The pencil line is where the tile trim goes. No bullnose on this one. 

Tom


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## Tom M (Jan 3, 2007)

I thinset the cracks and mesh and at times thinset seams for fill but use Aqua Defense to embed fleece in transitions. I dont know whats better or correct.


Just like the tub flange on acrylic tubs......the tile setter I use says he just packs it with thinset and mesh while setting but that seem like a crack waiting to happen to me. I may be wasting my time but I will silicone the gap the use Aqua defense in those transitions onto the tub for some flexibility.


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## tjbnwi (Feb 24, 2009)

I use Kerdi Fix to fill the gap, normally leave 1/4" gap, place a piece of band over it. Make sure you mask the tub deck if using Kerdi-Fix....

I also relieve the back so the board sits flat on the flange. No screws within 6" of the deck.

Tom


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## Tom M (Jan 3, 2007)

tjbnwi said:


> I use Kerdi Fix to fill the gap, normally leave 1/4" gap, place a piece of band over it. Make sure you mask the tub deck if using Kerdi-Fix....
> 
> I also relieve the back so the board sits flat on the flange. No screws within 6" of the deck.
> 
> Tom


Never used kerdi fix. I guess it's flexible/elastic.


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## tjbnwi (Feb 24, 2009)

Tom M said:


> Never used kerdi fix. I guess it's flexible/elastic.


Yes, and sticky as——well.....

Good luck getting it off something you don’t want it on. 

That’s why you tape off the deck completely. Leave yourself courtesy tabs to pull the tape off. Don’t run a piece of tape more than a couple of feet. Shorter pieces give you better control when removing the tape. 

Tom


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## avenge (Sep 25, 2008)

He didn't do the tile or backer he's left having to tape a seam 2" from the tile which is messed up. I almost always bring the tile past the seam, which ends up outside of any possible water if not I'll fibafuse, mud if needed then Redgard just short of where my tile ends.

And who the hell uses mesh tape anymore?


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## Tom M (Jan 3, 2007)

tjbnwi said:


> Yes, and sticky as——well.....
> 
> Good luck getting it off something you don’t want it on.
> 
> ...


Is it preservable? As in using today and cutting out a niche tomorrow and the tube still useable?


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## tjbnwi (Feb 24, 2009)

Tom M said:


> Is it preservable? As in using today and cutting out a niche tomorrow and the tube still useable?


Yes, I tape the nozzle or put a new one on the tube that has not been cut cut open. I've used tubes that have been open for 6 months or or more.

Tom


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## Big Johnson (Jun 2, 2017)

Tom M said:


> Is it preservable? As in using today and cutting out a niche tomorrow and the tube still useable?


https://www.finehomebuilding.com/20...206925d061aa64a398bb46db584c05c2d3e9f027f0f4a


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## Tom M (Jan 3, 2007)

Big Johnson said:


> https://www.finehomebuilding.com/20...206925d061aa64a398bb46db584c05c2d3e9f027f0f4a


I was literally reading this, this morning. Lol. This looks like it may work.


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## Big Johnson (Jun 2, 2017)

Tom M said:


> I was literally reading this, this morning. Lol. This looks like it may work.


I can’t tell you how many of those (pex with the plug) I’ve thrown away.


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## Tom M (Jan 3, 2007)

So on one of my jobs I tried this kerdi band on my seam and I'm regretting it.

I used guards to seal my drywall before thin setting the kerdi band to the seam. I have since skim coated the same with hot mud then all purpose joint compound and primer again.
My finish coat of paint is cracking all over the place.

Way too much work to be doing twice what could have been done differently?


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## tjbnwi (Feb 24, 2009)

Tom M said:


> So on one of my jobs I tried this kerdi band on my seam and I'm regretting it.
> 
> I used guards to seal my drywall before thin setting the kerdi band to the seam. I have since skim coated the same with hot mud then all purpose joint compound and primer again.
> My finish coat of paint is cracking all over the place.
> ...



Did the band stay in place? Did the hot mud not crack? Is the primer intact? 

I never prime prior to any type of banding or taping. 

Tom


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## Tom M (Jan 3, 2007)

The band is in place. The 45-minute did seem a little funny on the first coat and took more topcoating than it should have. The primer seemed fine too


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## tjbnwi (Feb 24, 2009)

I’m thinking the hot mud has issues.

I’ve had 5 minute take hours. 

Tom


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## artinall (Aug 14, 2007)

tjbnwi said:


> I’m thinking the hot mud has issues.
> 
> I’ve had 5 minute take hours.
> 
> Tom


 I'd call them up. Maybe they had a bad batch they're not telling anyone.


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## Tom M (Jan 3, 2007)

Although it was 45 minute I swear it acted more like twenty minute. Either way I hope to resolve it. I scaped anything that didn't bond and flaked. Then skimmed again.
Well see tomorrow


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## Tom M (Jan 3, 2007)

So this sucks more time and money wasted. Scraped the crackling paint which seem to moisten deeper layers.

Filled with normal spackle, after fully drying, put fresh paint on it only to get the same result.

Now I'm thinking it's the gardz. No problem with the thinset but powerful stuff wondering if it stays semi-active. Called USG they don't have any solutions unless you use their method for joint treatment


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## Tom M (Jan 3, 2007)

This, Sherman Williams says it possibly them but unknown. USG offers their own suggestion for this joint. Veering away kills a fix


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## tjbnwi (Feb 24, 2009)

Tom M said:


> This, Sherman Williams says it possibly them but unknown. USG offers their own suggestion for this joint. Veering away kills a fix


By now you're probably wondering if this works. 

The corner below is Kerdi banded (10"), taped and painted. Sorry, don't have a better picture. 

Tom


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## 91782 (Sep 6, 2012)

kilz


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## Big Shoe (Jun 16, 2008)

You guys never listen. Zissner Cover Stain oil primer anytime you think you may have bonding issues. 

First thing I do on a lot of jobs is roll a perimeter of repair area with it. Quick mud sticks and sets up faster on it. 

Tried Gaurdz once. Sorry, not for me. 


Sent from my iPad using Tapatalk


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## Tom M (Jan 3, 2007)

Thanks big shoe. I wasn't thrilled with the Gardz even if that wasn't the problem.

I will try cover stain


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