Disclaimer: I do not have any affiliation with 3M or any of its related companies or brands.
In a few months I'll be finishing 2 bathrooms at a new-construction investment property I'm purchasing.
And when I say "I'll be finishing" I do mean I will be finishing it.
I'll be doing most of the work myself, and I've been thinking about it.
You see, in a bathroom — a well-constructed bathroom, anyway— underneath the tiles is a layer of waterproofing. Sometimes it's a rubbery "paint", other times it's a special thin plastic-y/cloth-y membrane, or sometimes it's a special waterproofed foam board, or even something else... but whatever it is, the goal is always the same: to keep the water that will be splashing onto the tiles during your wild showers and baths from soaking through the tiles and into the construction underneath it.
Hold on a minute, water soaking through tiles?
Tiles are not waterproof.
That's right, in case you didn't know it: tiles are not waterproof.
They absorb water, but do so very slowly, and they don't absorb much.
But in wet areas like bathrooms, where tiles have water splashed on them on a regular basis (oftentimes daily), that water can have enough time to soak through the tiles and through the adhesive holding the tiles to the wall/floor/ceiling (which is also not usually waterproof).
And that's okay.
The tiles and glue can get wet, no problem. They are designed to get wet. And it's especially not a problem if they regularly have time to dry out between getting wet...
But there is a problem.
The stuff underneath the tiles and glue? That should not get wet.
Under the tiles in your bathroom, you will oftentimes find drywall, wood, concrete, etc... All things that should not get wet and stay wet.
The construction underneath your tiles is not designed to get wet. It usually does not have any access to fresh air, so once it gets wet, it will stay wet. And if it stays wet, depending on what it is, it will do one or more of these many, wonderful things: rot, decay, or degrade. And if it does any of that for long enough, it will eventually fall apart (along with your bathroom wall, or in more extreme cases: a whole chunk of your house) or become a health hazard.
So the construction under your tiles must be protected. But how do you do that?
Put something waterproof underneath the tiles that keeps water from going any deeper than the tiles and adhesive.
Boom! Waterproofing. Some rubbery, plastic-y, cloth-y junk... whatever. Problem solved.
But not so fast.
One tiny flaw in your waterproofing can cause a complete failure of the structure underneath.
Imagine trying to waterproof the inside of a cardboard box in such a way that you can fill the box up with water and none of the water will seep through to the cardboard...
But If you miss even a teeny tiny spot, there is a place for water to get past the waterproofing and get soaked up by the cardboard... and we all know how strong and durable soggy cardboard is...
While dry cardboard is impressively strong, wet cardboard can be picked apart by a sleepy baby.
And you know what else is great about cardboard that gets wet? It wicks the water, which means that even if you only have 1 tiny hole in the waterproofing of your cardboard box, the water will slowly seep through the 1 tiny hole and then wick to other parts of the box, possibly even the entire box.
One tiny hole, the entire box is as good as garbage.
Hmm, this cardboard box, it's actually a lot like your bathroom...
You know what else is great at absorbing and wicking water? Drywall, wood, concrete... yeah, just about anything that you can find under your tiles.
And you know what else gets weaker when it gets wet and isn't allowed to dry? Drywall, wood, concrete... you get the idea.
Okay, but let's say you manage to perfectly waterproof all the surfaces under the tiles in your bathroom.
Good job, you.
The whole thing can get flooded and not a drop of water will soak through the walls or floor (well if it was flooded, the water would start going out the door and ruining the rest of your house but, let's just ignore that for now).
Can you drill holes through the waterproofing?
Now let's say you want to hang something in your bathroom, perhaps a little shelf on the wall in the shower where you can put your Mane 'n Tail shampoo and Verticoli hair brush?
Who am I kidding, you wouldn't keep a Verticoli in your shower.
But as far as the Mane 'n Tail goes...
Traditionally, you'd drill a few holes through the tiles and into the wall underneath, insert anchors into the holes, and screw the shelf into the wall, and presdo!
Whoa there, speed racer.
Your perfect waterproofing has just been compromised. You've just created a "teeny tiny hole" in your cardboard box. And all that time and effort you spent perfectly waterproofing your bathroom you may as well have spent spraying your precious drywall with a fire hose.
I may be exaggerating, but only slightly.
Traditional anchors are not waterproof. If you use a regular ol' wall anchor, there are tons of tiny passageways that water can now take to get past your waterproofing. E.g. it can seep behind the screwhead, in between the anchor/waterproofing, and into the wall underneath, or just go between the screw and anchor and into the wall.
One tiny point of failure... but the potential to slowly destroy your entire bathroom, or even house.
How to drill holes through waterproofing without compromising it
Regular anchors and silicone
But let's say you're smart. Let's say you knew that a hole would compromise your waterproofing and that a run-of-the-mill wall anchor isn't waterproof, so you filled the hole with silicone before inserting the anchor. That should seal up the hole nicely, right?
Actually... Yeah. Probably. A lot of people do this, and it's probably enough to get the job done.
But something just does not quite sit right with me and this method. You're relying on having a full and even application of silicone all around all the areas that water could possibly seep through, and you're relying on the silicone bonding to the anchor, waterproofing, and screw (so hopefully each of those was perfectly clean when you installed them). And that's not to mention that you cannot visually inspect the silicone application, so you have to just hope that the silicone reached every area it needed to and that it bonded well.
But is there even a better solution?
Some companies make special, sealing anchors just for applications like this. They are designed to nicely seal the hole once one of the screws provided with them is driven into them.
These types of anchors are probably the most "correct" way of drilling a hole through waterproofing to mount something on a tiled, waterproofed surface.
And as a matter of fact, I purchased 2 boxes of these kinds of anchors in preparation for finishing my bathrooms.
But I still could not sleep soundly at night. Even these anchors, which are designed by smart people to do exactly what you want them to do... they just don't sit quite right with me, either.
The problem with sealing any hole you drill into waterproofing...
Whatever your waterproofing is... rubbery paint, plastic-y membrane, special foam... it doesn't matter: it is not thick. Usually it's no more than 0.5 mm thick. When you drill a hole through that waterproofing, you are only exposing a tiny amount of that waterproofing.
If your waterproofing is 0.5 mm thick, drilling a 6 mm hole into it exposes only about 9 mm² of your membrane. That's about 30x less than the surface area of the face of a U.S. penny.
And regardless of what you use to seal the hole, you are trying to get some kind of sealant to seal against that measly 9 mm² of surface area.
You have practically zero margin for error.
You need something to seal or bond perfectly with every single one of those 9 square millimeters of exposed waterproofing, or you will no longer have a perfectly waterproofed wall.
"But professionals have been sealing like this for years and everything is fine."
Yeah, you're right. The silicone method, it's great. Sealing anchors, they're great. Installed correctly, either of these things should last longer than the style of your bathroom, and by then... you'll likely be thinking about your next remodel, anyway.
But listen, I'm crazy.
I can't accept "good enough" or "probably".
Is there not a way NOT to compromise the waterproofing and sleep soundly at night?
Oh, there is.
The best way not to compromise your waterproofing
If you don't want to compromise your waterproofing, just don't drill through your tile in the first place.
Don't drill through anything.
Okay... sure, but then how do you hang things like shelves, toilet paper holders, mirrors, etc. on tiled surfaces?
Well, not just any tape.
3M VHB tape, the king of double-sided tape
3M VHB tape is a line of high-strength, closed-cell acrylic tape.
The name of this tape — "VHB", which stands for "very high bond" — does not do it justice.
This isn't the Scotch tape in your aunt's gift-wrapping station.
This stuff is certifiably insane.
This tape should be kept behind locked doors, in a padded room, with 24/7 surveillance.
It's stupid strong. Like, if an elephant stepped on a pad of this stuff, it would rip the floor out before the tape failed.
Not only is it strong, but it stays strong, permanently.
This tape is not a temporary solution for anything. Once you apply it, you're not peeling it off. Forget about taking it off without using power tools (that is literally how 3M recommends removing it, if you must).
So if you do decide to use it for anything, don't make any mistakes, because taking it off is a ROYAL pain.
Did I say this stuff is strong? Well if you think it's strong, wait a few days. Because it gets stronger the longer it's left in place.
The more time the tape has to bond to the surfaces it's attached to, the stronger that bond gets. According to 3M's design guide, it reaches just about its full strength after 72 hours at room temperature, and according to their long-term testing, nothing suggests that it gets weaker over time. If anything, it gets stronger still.
If that wasn't enough:
- it's waterproof
- it creates a watertight seal
- it can stand arctic cold
- it can take desert heat
- it dampens vibrations (not to mention it can withstand just about any kind of vibrations)
- it dampens noise
What's not to love about this tape?
The limits of 3M VHB tape
Now, of course, this tape is not magic. It has its limits. And you have to be smart about how you apply it.
Strength vs. space
With a screw, you have a lot of holding power with just 1 small hole.
If you want to use this tape, you need a lot of surface area. The more surface area you can cover, the stronger a hold you will get.
With a screw, you can pretty easily remove whatever you mounted with it any time, and then put it back.
If you want to use 3M VHB tape... then as I mentioned before, this stuff does not come off easily. You should not mount anything you anticipate removing anytime soon.
And while it is a permanent solution, it will slowly degrade if exposed to direct sunlight or harsh chemicals for long periods of time (and by long time, I mean months, if not years).
In most bathrooms, neither of those are a problem. There is no direct sunlight and there are no harsh chemicals constantly washing over anything.
So used to fasten anything in a bathroom, 3M VHB tape should outlast you, your kids, and their kids.
Proper application of 3M VHB tape
Always read the instructions before using a product like 3M VHB... especially if you'll be using it for critical things like... I dunno... your entire bathroom.
But as with just about any adhesive product, proper preparation is key. If possible, use sand paper so that you have abraded, rough bonding surfaces.
Then clean your bonding surfaces to perfection. They should be darned-near sterile and completely free of dust.
3M then recommends a final wipe-down with a 50-50 mix of isopropyl alcohol and distilled water.
You should also use 3M's recommended primer (which may vary depending on the surface you are trying to fasten to).
Once the bonding surfaces are totally dry, you can fasten them to each other using the tape.
Use a roller and light-medium pressure to apply the tape where possible.
3M does not recommend applying the tape in ambient temperatures under 10 °C.
Do not base anything you do on what I've written here. Refer to the instructions for the specific model of tape you purchased.
How I plan to use 3M VHB tape in my bathrooms
Except for incoming water pipes and electrical wires — which I will have to make holes for — I do not plan on drilling a single hole on any surface in my bathrooms. Literally anything that will be fastened in my bathrooms, will be fastened via 3M VHB tape. Or it will be bolted or screwed to something that is fastened via 3M VHB tape.
I plan on fully waterproofing and tiling every surface of my bathrooms, except for the ceilings. And then I will install any fixtures atop the tiles. This way, if anything fails... like an in-wall toilet unit, or bathtub drain, water will have no reasonable way of seeping through to the concrete or drywall under my tiles.
That means if something fails... easy clean up, easy repair. No fussing around with fans and towels for weeks, trying to dry out your water-soaked concrete floor.
In-wall toilets are popular in Europe. And for good reason. They are more aesthetically pleasing than free-standing toilets, and they are easier to clean (you don't have to get behind them, you can't, they are literally in the wall).
I have a love/hate relationship with in-wall toilets. I love them for all the reasons I just mentioned, and more. But I have always hated the idea of having a complicated water device with numerous connections and points of failure embedded in your bathroom wall, behind permanently installed tiles.
What if an in-wall toilet fails or needs maintenance?
Generally speaking, these in-wall toilets have been used for a long time all over Europe, and are reliable and require little to no maintenance.
But what if something were to go catastrophically wrong with one of these toilets?
Well, then you'd better hope you can fix whatever the problem is through the access panel, which is about the size of an A5 sheet of paper. Otherwise, your only option it to tear it out of the wall. You did keep spare tiles around from when you renovated your bathroom, right?
My in-wall toilet plan
But the way I plan on installing my in-wall toilets is certainly not going to be standard. They're not going to be "in" the "wall" at all.
First of all, as I mentioned earlier, my entire bathroom will be waterproofed and tiled. And I will install the in-wall toilets on top of these tiles.
Well that sort of defeats the purpose, no?
No. Because I will then cover them with my own "wall" that I will make out of wood.
The toilet will be mounted to the bathroom floor and wall in the same locations that normally call for screws, but instead of screws, I will use 3M VHB tape. Luckily, these mounting points have a large surface area, which I believe will be enough by themselves to safely fasten the toilets to their mounting points. But if it turns out that it is not enough (which I will decide on the spot), welding or otherwise fastening larger plates to these mounting locations will not be a problem.
Once the toilets are fastened in place and connected, I will fasten large, square studs to the walls around them via 3M VHB tape, and to these studs and the toilet frames I will fasten my wooden wall via traditional screws and/or bolts.
I will leave 8–16 cm of space between the base of the wooden wall and floor, that way, if the toilet starts leaking, it will spill out visibly onto the floor at which point someone will hopefully notice and take action.
With this installation, having full, unhindered access to the toilet is just a matter of removing the toilet bowl and 8–12 screws.
Destroying your bathroom wall vs. removing a few screws... I like my idea better.
I will fasten the bathtubs in my bathrooms to the wall with 3M VHB tape.
I will use the mounting brackets the bathtub manufacturer recommends as well, but I will mount them to the wall with... you guessed it, 3M VHB tape.
I will also likely fasten the legs of the bathtub to the floor using 3M VHB tape.
To mount the bathroom mirrors, I will use 3M VHB tape to fasten a French cleat to the walls above the sinks. The French cleats will be just a little bit shorter than the full width of the mirrors I will hang.
Then I will attach another French cleat to the frame of each mirror I want to hang, probably using stainless steel wood screws (and being very careful not to damage the mirror glass).
And then I will hang the mirrors via the French cleats.
The French cleat is a great option for this because as I said earlier, the more surface area you have for mounting, the stronger a hold you will have. And to get a huge surface area, I will use something like a 10 cm-wide board to make the French cleat which will be fastened to the wall. That, and I will make it as long as possible, nearly the full-width of the mirror that will be hung.
That will be a lot of surface area, about 600 cm² to be exact. Which, according to 3M's recommendations, is enough to hang almost 11 kg with a large margin of safety. The mirrors I plan to hang are less than 8 kg.
While that much tape just for a mirror is probably overkill, I do not want to risk a mirror falling on anyone, so I want to make this connection extra strong.
I am planning on fastening the bathroom vanities to the walls they will be put up against similarly to how I will hang the mirrors, but instead of French cleats, I will just fasten a piece of wood to the wall in each bathroom, and screw the back of each vanity to those pieces of wood.
Since the vanities are much less mission-critical than the mirrors (i.e. they cannot fall off the wall and hurt anyone), and most of their weight will be supported through their legs and the floor, I will use less tape.
The legs of the vanities I will be building will hold the weight of the sinks and anyone leaning on them, so the purpose of fastening them to the wall is just so that they cannot move around, which would be annoying, and could possibly damage the hard-line drain pipe that will be attached to the sink.
Shower curtain rods, toilet paper dispensers, towel racks, etc.
Small bathroom mounting accessories? Easy.
I will either purchase products which have large mounting surface areas, or custom-make my own.
And that's the plan for my investment property bathroom finishing! I'm very excited.
But you know what I'm more excited about?
No lie, you reading this entire blog post... Are you kidding me!? Hopefully you didn't just skip down here, because I am freaking out right now.
You are the best. Thank you for being here, I hope you learned something, and I hope you have an awesome day and/or time using 3M VHB tape!
I will most certainly post an update once I finish the bathrooms... and probably a few years in the future to report on how well the tape is holding up. Which I am confident will be: great.