Chaulk or Grout? Getting rid of the gap on a Kohler Underscore Tub
This Kohler tub is a really poor design for the undermount look. For starters the tub is pitched on the edges a fair bit. This creates a natural shadow line. Add in a poor slab install. A crappy job from the builder building the tub deck. A plumber that in my opinion needs to retire and you are left with a challenging finish job.
I have agonized over this minor detail and yesterday took the first steps to improving the look of my clients master tub installation.
The gap between the bottom of the Ceasar Stone Slab and the tub was in places a good 3/8" thick. Other more like 1/4" or a hair under. You can see the tile shim and the gap here.
Gap varies 1/4" to almost 3/8"
My first thought for this gap as to use a plastic Schluter profile to fill the space but after trying to make some nice curved bends the look is not as nice as I would have liked. I decide to abort that plan and choose between silicone and grout. I thought Silicone would be easy but in the end look cheap. So I decided on grout.
So I had to choose between urethane, cement or epoxy. I think urethane grout is crap so that was out right away. I then thought the regular grout would be easy to install but I was worried about the bite to the tub deck and then decided the only safe bet as epoxy. Epoxy grout is not cheap and I was not going to fill these huge gaps (some spots it goes back almost 2") since grouts tend to shrink back a hair and if the space is uneven the shrinkage can vary.
The next step I thought was to fill the space with a rapid setting thin-set mortar. I choose Ardex X32 for this.
X32 Grout Installation tool
I used my hand and fingers to force the X32 back into the void. You can see all the care I took prepping for this task! lol NOT. The filling took longer than I thought and the process was almost 45 minutes long. Then I needed to clean up the mess before it got to hard to clean up the mess. I can not believe how sharp the stone was. It sliced my finger up just racking the X32 away.
Cuts from Ceasar Stone Bottom Edge
Filling the gap
Once the X32 was installed I then further pushed it in with a sponge and my finger. I used a sponge to clean the tub, the stone and the smooth the edges. X32 is very course and leaves a nice rough surface after tooling still. This will be perfect for added bond strength for the Epoxy grout later.
Now none of this is approved by anyone. Lets get that straight from the start. If we follow Kohler's advice we would use latex chaulk and only enough to barely hold the stone in place. Kohler wants these materials removable - why? I have no idea but this direction is clearly out to lunch.
Ardex makes epoxy grout - but I have never tried them. I like one epoxy grout and it is made by laticrete and called SpectraLock Pro. So that is what I will use later tomorrow to fine tune this install.
The X32 in these pictures is fresh so it looks a little off white. Once it dries it will be bright white and look a little closer to the finished product.
All cleaned up
I then spent another hour detailing out the tub. The plumber on this job used his grinder in the bathroom over the tub and left all these tiny shavings behind. They left little rust spots that took forever to buff out with my scrub pad. The stickers came off finally and the tub looks better all ready.
The anti slip pads still look a little off white and I will later try and clean that up with some Goof Off I think.
The lesson from the School of Hard Knocks on this job I think is to prepare the slab better and the tub deck. The next time we do this install I will get the slab guys to add a sliver cut of Ceasar Stone 1/4" - 3/8" thick to the edge and then back cut that with the grinder and polishing pad a few degress so it can sit down flush with the tub. This will I think really simplify the job.
I'll post some pictures next week when this job is wrapped up. Glass goes in next week. Grout is wrapping up on Saturday. Going to look amazing.
Comments (18)
User
8 years agoMongoCT
8 years agoRelated Discussions
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By Any Design Ltd.
8 years agoThanks Mongo. I thought about that but did not think a trip to the hardware store would be worth the material savings of the X32 used. I also felt like the X32 would be a stronger backer for the Epoxy grout.
Your right as well that this was more of a blog style post. These Kohler Underscore tubs are very popular and I'm sure many people find themselves in the same boat.
This being the second of mine in less than a year.
The other one I hope to fix up the same - if the client has not all ready siliconed the gap.
I hate the shadow line created by the slope on the Kohler tub. You would think a company as large as them could figure this out. But nope. 
PROMint tile Minneapolis
8 years agolast modified: 8 years ago- PRO
By Any Design Ltd.
8 years ago palimpsest
8 years ago
PROJoseph Corlett, LLC
8 years ago- PRO
Mint tile Minneapolis
8 years ago - PRO
Joseph Corlett, LLC
8 years ago - PRO
By Any Design Ltd.
8 years agolast modified: 8 years ago - PRO
By Any Design Ltd.
8 years agolast modified: 8 years ago - PRO
By Any Design Ltd.
8 years agoYesterday I went back and applied the Epoxy Grout to the tub. I used Laticrete's SpectraLock Pro Epoxy grout and only mixed roughly a 50% mix. I added a hair more powder to make the mix a little stiffer than specified on the package.
First thing I did was clean the tub again and buff out the edge on top. Then I taped off the area that would not see grout and protected the blower holes from dropping epoxy grout.
I rammed the grout into the little void again with my finger and smoothed it close. I did this all around and then before using any sponge removed the tape.
This left the job a little rough - so then I went back with the sponge and my finger (this time without the glove) and smoothed things down. The uneven height change made it hard to keep super even so I took my time and slowly added and removed a little grout here and there. I found using the baby sponge that came with the grout perfect if I used it like a block plane and gave almost no pressure.
Then a smooth with my finger and it looked great. Took me two hours just to prep for grout, grout and clean up.
Quite a change from last week. No more shadow lines and the colour is almost a dead match. I find that epoxy grouts darken a little as they dry and have not yet used LAticrete's white so I hope this will not happen much. Right now or rather yesterday when I left it was like Laticrete made this grout colour for the Blizzard Ceasar Stone Slab.
Looks so much better and hopefully will stay put and make cleaning the tub a little easier for my client. User
8 years agolast modified: 8 years ago- PRO
By Any Design Ltd.
8 years agoLooks freakin amazing if I do say so myself. The epoxy grout deep deepen in colour a hair but looks great still beside the Blizzard Ceasar Stone Slab.
What do you think?
Undermount Bathroom Tubs · More Info
Still need to touch up the grout here and there. Some more silicone work. Re hit the miter joints around the window but this puppy I think is almost ready for a test drive. - PRO
Joseph Corlett, LLC
8 years ago bsauriol77
6 years ago
thatsmuchbetter
6 years ago
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