Overkill is a part of my soul.

There's little I like more than overkill. If I were a professional wrestler, my name would be "Overkiller!" And my finishing move would allow me to pin you to the count of six rather than only three. But my entrance music would surely be the excellent Men at Work song, Overkill...of course.

Whether I'm over engineering a software solution for work, or over analyzing the premise of a television commercial, there are few things I like doing more than over doing things.

Much to Wendy's dismay, my propensity for overkill has a corollary impact on most, if not all of our house project timelines.

With a tilt of my head and a raise of my eyebrow, a simple weekend project can be quickly stretched to weeks or months. This skill would be my power if I were the lamest superhero in the world, Overkill Man.

"Oh, you just want to paint that room? That looks like a job for Overkill Man!"

"Many people can get this done in a day, and paint is all that's really needed...But, I'm going to just throw this out there. What if we also add a speaker in the ceiling? I mean, I've already run the wire, it's just a matter of putting in the speaker."

"Now that the speaker is there I noticed a bunch of cracks in the ceiling. What if we just quickly put up some plaster buttons and then skim coat that crack...or maybe skim coat the whole ceiling if you think that might be better? I think it'll look way better and will totally be worth the effort."

"Now that the ceiling is done the walls look really bad. We should skim coat those too, but since we're skim coating let's take down the molding so we can put up something that's supposed to be there. I've always hated what's there, it's just wrong."

You see where I'm going? Yep, off the rails on the overkill express, and I'm the captain. Captain Overkill, if you will?

You want an over engineered solution to any problem? Come to me and I'll help you achieve your dreams.

Our master bathroom project has been an exercise in overkill. It's so textbook, my name could be Professor Overkill, PhD, and I should be teaching a class. We've got speakers, and salvaged closet walls, and network cables, and rain shower heads bigger than, well, your head.

But our latest layer of overkill is, well, completely and totally necessary, in an overkill sort of way. Trust me, I'm a doctor/wrestler/conductor/superhero remember, and I'm almost positive I'm right!

In a bathroom full of moderate to significant expenses, our choice of 1" Carrara marble hex throughout the space is up there on our bigger ticket item budget tally. The last thing I want to do is make some misstep during install that leaves our tile looking old and damaged when it's really shiny honed and new.

I've already told you about the Hardi backer we put down around the edges of the room, as well as the self leveling underlayment we poured over the radiant heat mat.

After that saga we had to bring the cement level with the Hardi backer so we applied a bit of thinset to the top to bridge any height changes. This thinset also filled in the gap left when the self levered leaked into a void in the corder.

Any reasonable person would have simply taped the joints and called it a day, having a suitable underlayment for tile. But I am no reasonable renovator. I want to make sure it's going to be sound and sturdy, no chances of cracking.

In steps the NobleSeal TS sheet isolation membrane.

Many of you are likely familiar with the orange waffle mat isolation member called Ditra from Schluter. You know, the rolls you see at the big box and all of the DIYer blogs use it in their laundry rooms or bathrooms.

This is an isolation membrane, and it's purpose is simple. The sheet sits between the substrate (floor) and your tile, and ensures any minor movement in the floor, such as through seasonal expansion and contraction, is not transferred up through the floor and into your tile and/or grout. In short, the isolation membrane helps prevent cracking in your floor.

But you have to read the fine print on Ditra. The documentation from the manufacturer says, "not for small format stone or tile less than 2" x 2" square. But why?

Ditra's waffle pattern gets filled in with thinset and your tile is set upon that. This works great for the isolation of large tiles by placing the tiles on little pillars of cement all over the room. With large tiles, the weight is nicely distributed across the waffle by a series of little cement columns.

However, if you have small format tiles, the distribution of weight may not sufficient, and you can end up with partially or completely unsupported sections of tile. Add some point pressure, like that from the foot of a clawfoot tub, or the massive pressure from the tips of a pair of high heels, and you can end up with a cracked tile and hole in your floor. 

It is worth noting that the maker of Ditra has given conflicting information on this topic and you'd likely be just fine if you pre-skim the Ditra with thinset to fill voids, but the documentation does specifically state this.

Fun fact, an average height and weight woman in a pair of high heels inflicts more pounds per square inch of pressure with her heel than a full size elephant does across their foot.

Since we're opting for a 1" marble hex tile we need a different isolation membrane. I also want to limit any unnecessary additional height in our floor. This is why we chose to use NobleSealTS. It adds only .030" to the install height, comes in a roll, and offers superior isolation and crack resistance in the installed tile.

We actually used it a few years ago when we were doing our vestibule project, and I really liked how it worked. But that was in a very small area, this one was going to be across the whole bathroom.

We kicked off this phase of overkill by first unfurling the roll of NobleSeal membrane in a completely empty bathroom. This allowed us to fit the entire room with the necessary pieces before putting down any bonding agent.

Preparing each piece is quite simple. I like to use a sharpie to mark my cut line, as it tends to work perfectly on either the rubber or the felt part of the membrane. You can also fold and crease the material and use that as a cut line, but it feels less exact.

Cutting the NobleSeal is very easy with scissors or a utility knife. The material is thin and pliable and actually acts like good wrapping paper when you start to cut it. By that, I mean that the scissors can just slide along and make a good clean and nearly effortless cut. 

Not at all like the cheap wrapping paper that Wendy's always buying for $1 that's too thin and tears as you try to slide your scissors. That sort of paper makes me hate my life. And don't get me started on wrapping paper that doesn't have a grid printed on the back of it.

After the sheets were all laid out in the room we needed to vacuum everything thoroughly, both above and below the membrane. Sometimes it's best to have a helper at this stage of the game.

As you can see, any helper will apparently do.

There are several ways to adhere the membrane to the surface, both using Noble's proprietary glue/cement, or using standard latex modified thinset. We decided to use the thinset as it's less expensive, easy to get (I like the Kerabond brand), and we've worked with it before. 

It's important to note that the product calls for latex modified rather than a non-modified thinset. The Schluter products all call for non-modified thinsets, but not the Noble products.

Mixing up the thinset is done per the bag's specifications, but I tend to go to the looser side, meaning adding more water than less. Application of the thinset is done by troweling it on with a 1/4" V-notch trowel. I typically start by laying it all onto the floor with a taping knife first, then scraping it off with the V-notch trowel. It takes a bit longer this way, but it really ensures full coverage and no gaps.

Once thinset had been spread in the area we were working, we laid the membrane down to embed it in the thinset and began rolling it out with a three wheel hand roller. 

While you can optionally use a 100 pound linoleum roller for this job, I instead opted to leverage my massive 150 pound hulking frame and the wonders of gravity. In retrospect, the linoleum roller would have been a much wiser choice. 

Working from the inside out, and with the lines applied from the v-notch trowel, my goal was to squeeze as much of the thinset out from under the mat to give a smooth and consistent surface with full coverage. The key to the overall success of the mat is a consistent and even bond with the floor beneath. 

After about four hours of methodical work, a whole lot of sweat, two batches of thinset, more curse words than I could count (I get stressed when working with thinset), an aching back and two very sore arms, we had ourselves a bathroom with a successfully laid isolation membrane.

Applying the isolation membrane gave me the overkill I was searching for and ensures our tile floor will not crack during the next Virginia 6 plus magnitude earthquake. What's more, it's the final step before we start laying our tile. 

We'll need to let the thinset fully cure before we launch into that phase of the project, but both Wendy and I are beside ourselves excited that we may have an actual and somewhat functional bathroom before long. I won't get crazy and start thinking about the "D" word, because that's a long ways off. And in case you're wondering, the "D" word I'm referring to is "done," and not "divorce." But the latter "D" word could very well happen sooner than later if we can't achieve the other "D" word on this project before too much longer.

Comments 17


6/20/2014 at 3:56 PM

I don't think that's overkill at all, especially for older houses whose subfloors or joists might be just a little more flexible. I'd always use some kind of membrane installing tile unless it was over something like a concrete sub where I knew there'd be no movement. I had no idea about the Ditra and tile size, thanks!


That's exactly my thought with our house. I mean, I know the joists are big and strong, and I'm relatively certain the deflection is low enough and cement board sufficient for the stone, but why risk it? Why not know that I went the extra step necessary to ensure a good install?

6/20/2014 at 8:50 PM

Tiling is next! Time has just flown by. I've been following your blog for only about a year now, so in that short time--to me--you have bought your home, made major repairs and upgrades, had a lot of parties, earthquake, snowmaggedon, and now bathroom tiling. Don't stop now. Cheering you on!


Thanks, Mia! Very much appreciated.

6/21/2014 at 12:55 PM

This entry was very funny. Almost spewed Monster across the screen at one point. Don't ever stop being Captain Overkill! (Sorry Wendy!) I can so relate to the overkill process. Or project creep as it's known around these parts. Your bathroom is going to be so awesome!


Yep, I know it as scope creep for me in my day job. Always with the customers asking for more than originally specified. At least in this case, I get to be the customer too.

Franki Parde
6/21/2014 at 5:34 PM

Good gosh...are you related to my husband?!?!?!?!?!? franki


Great minds. Alt wink

6/23/2014 at 11:45 AM

I had a question about the heated floor option. I haven't done much research into the topic so bear with me. It seems that there are a lot of layers between the heating element and the actual top layer of the tile (SLC, thinset, membrane, more thinset, tile). Is the heating element strong enough to make a noticeable difference through all those layers? Then if something goes wrong with the heating element, will you have to jackhammer through all those layers to fix the problem?

Just curious as we would love to add heated floors to our own home...down the line.

6/24/2014 at 1:19 AM

Rachel, I ended up with staple up hydronic heat under my bathroom floor, tacked on to my hot water heat system. The heat has to go through the subfloor, original heart pine floor, cement board, thinset and porcelain hex tile. And you can feel it! I haven't put the insulation layer under the tubing, so much of the heat dissipates into the basement, it will only be better once I get around to doing that. I've been in many showhomes with electric heatmats and the floors are toasty warm. I have often wondered what happens when/if the element fails...


One of the major things we did included the placement of insulation below the heated section of the floor. This should help the heat go up and into the floor where we want it to go. We'll see once we get to the winter, but it's my hope this heating element is sufficient for the whole room and we can just close the forced air vent.

6/24/2014 at 7:07 PM

There may be things you do that are overkill, but an isolation membrane isn't one of them! Thanks for the brand info!


Glad to be informative.

6/26/2014 at 7:37 AM

Great post, and Captain Overkill has his place, keep on keepin on. I've never even heard of Noble Seal thanks for the tip about Ditra


Glad to be of assistance on that one. Better to learn this way than the hard way.

7/9/2014 at 1:58 AM

Our Ori Peis look almost identical -- especially the 'why the heck are you taking my picture' look. Mine also had two potentially cancerous mast cell tumors removed when she was four. She went through radiation and all that and is 8 now and doing wonderfully, although I'm a bit worried that the arthritis the radiation doctors warned about is beginning to set in. Is there a way to send you guys photos?

3/20/2018 at 9:44 PM

Hope you don't mind such a behind-the-times question, but I wondered whether your bathroom floor hex is polished, honed, or tumbled? I've been on a polished marble floor that was dangerous when wet, but it was 12" tiles, not little hex.

Any regrets on your floor choice?

Great job on your house! Wish we had 1/10th the energy and stick-to-it-ness you guys have!

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