Bathroom subfloor materials

[MEDTECH]

It's about time to re-do our 5x7 bathroom and I'm just looking to get some input.

For the subfloor, would marine plywood make a good choice? Just looking for a material or possibly a membrane/coating that would reduce the chances of water damage/rot in the future.

Unsure if I wanna do ceramic tile or a vinyl or other durable layer.

 

[cgrutt]

If you're going to tile it I'd use Schuluter Ditra isolation membrane over thin hardiboard. Not sure if the chemicals in marine plywood are good idea to bring into house. Haven't tried this before on a floor but if you're going to use vinyl maybe use a standard plytanium type underlayment and paint it with a waterproofing membrane such as Mapei aquadefence?

 

[MEDTECH]

If you're going to tile it I'd use Schuluter Ditra isolation membrane over thin hardiboard. Not sure if the chemicals in marine plywood are good idea to bring into house. Haven't tried this before on a floor but if you're going to use vinyl maybe use a standard plytanium type underlayment and paint it with a waterproofing membrane such as Mapei aquadefence?

Good info; thanks. I'll start my research.

Never thought about the marine plywood potential for issues

 

[MEDTECH]

Should also mention that I am contemplating a shower/tub surround. With 4 people constantly taking showers (we only have 1 bathroom), I'm trying to minimize grout cracking and water penetration points.

 

[cgrutt]

I'd tile with the Ditra isolation membrane. You can also run Schluter Kerbi water barrier on joints and around perimeter of room (1/2 on floor 1/2 on wall behind moldings etc) to completely waterproof it. The isolation membrane does a great job at preventing cracks. Also be sure to use a good fortified grout. I like Mapei for grouts/thin set etc.

 

[rlitman]

I went with Advantech subfloor (it's more waterproof than marine ply, and stiffer as well), but you still want a membrane over it to block water. I used Laticrete Strata-heat mat (basically Ditra heat mat) with double flocked tape at the seams and up the walls and pre-formed corners.

These Ditra type isolation membranes come in three thicknesses. Standard is thinnest, the electric cable heat types are all 1/4", and an XL type made for natural stone is slightly thicker. Laticrete's product is milky translucent, which lets you see the thinset coverage through it, making the install a little safer than the opaque orange.

I just found this picture I took before we filled in the mat level with the tops with thermal thinset. By my left foot, you can see one ribbon of tape at the threshold protruding from under the mat seam. The rough-ins on the bottom left are for the wall hung toilet, and the heat cable does not run under the vanity. The floor drain went over this (a Kerdi linear drain was used), and the tub is now in the alcove up top.


If you look REALLY closely, you can see some orange from the Kerdi pre-formed corners at the top corners of the mat. The floor slopes towards the linear drain (like a shower pan, but this is NOT a shower), so I didn't bother with the high corners at the bottom. The blue tape was a cheap Kerdi knockoff (I wasn't concerned with manufacturer warranties).

 

[duneslider]

I went with Advantech subfloor (it's more waterproof than marine ply, and stiffer as well), but you still want a membrane over it to block water. I used Laticrete Strata-heat mat (basically Ditra heat mat) with double flocked tape at the seams and up the walls and pre-formed corners.

These Ditra type isolation membranes come in three thicknesses. Standard is thinnest, the electric cable heat types are all 1/4", and an XL type made for natural stone is slightly thicker. Laticrete's product is milky translucent, which lets you see the thinset coverage through it, making the install a little safer than the opaque orange.

I just found this picture I took before we filled in the mat level with the tops with thermal thinset. By my left foot, you can see one ribbon of tape at the threshold protruding from under the mat seam. The rough-ins on the bottom left are for the wall hung toilet, and the heat cable does not run under the vanity. The floor drain went over this (a Kerdi linear drain was used), and the tub is now in the alcove up top.


If you look REALLY closely, you can see some orange from the Kerdi pre-formed corners at the top corners of the mat. The floor slopes towards the linear drain (like a shower pan, but this is NOT a shower), so I didn't bother with the high corners at the bottom. The blue tape was a cheap Kerdi knockoff (I wasn't concerned with manufacturer warranties).

I am in no way trying to be a jerk but I am super curious what you have going on in that picture, that laticrete mat is not waterproof? Not sure how that is going to work with a linear drain? Also, Advantech isn't waterproof, it is pretty water resistant but it def isn't waterproof. I haven't used strata-heat since it first came out, so it is possible something has changed but based on the current literature I don't think anything has changed. I will say I think their spec sheets on this stuff aren't great and are a bit hard to understand.

Anyway, I am totally a laticrete fanboy, so I love their stuff BUT Ditra and Stratamat are NOT the same. They are both uncoupling mats but Laticrete's product has "Hydration Vents" ie holes in the mat, so it is NOT waterproof like ditra is, which is completely continuous and waterproof. I just want to make sure people know that you will not get a waterproof floor with laticrete's mat like you will with ditra. I've been using ditra and kerdi forever but for the most part only do hydroban showers now. In bathrooms and laundry rooms I always use ditra. If I am not going to be doing wet areas I will use stratamat.

Anyway, It always frustrates me to see people comment about wanting to use drop-ins or inserts instead of doing a tiled shower because of a belief that tile leaks. A properly done shower, of any style, will be waterproof and not leak. Exactly zero of the showers I have ever installed have leaked. Even if grout cracks, nothing should leak. Grout and tile are there for looks, not to waterproof. Now, I have made a lot of money replacing showers that were not done correctly and that is very unfortunate for those people who had to go through all of that drama.

 

[MEDTECH]

I appreciate your experience as a contractor. I'm just in the learning phase so all information is welcome.

I'm going to have the remodel done professionally as I don't have the experience nor am I physically able to crouch down and set/grout tiles due to arthritis and other joint issues.

I've seen quite a few videos on YouTube about the "correct" way to do a remodel and, like most things, there are differing methods and techniques and materials to decipher.

In my area, even a small remodel can easily cost 10K or more so I'm just trying to get as much knowledge as I can before I chose a contractor.

As you say, "properly installed" is key so I need to educate myself so that I can talk intelligently with the contractors that I will speak with.

 

[theoldwizard1]

Old school. Durock or other cement board.

Really old school is tar paper on the sub-floor and about 3/4" of mortar. Let set for at least 24 hours.

 

[rlitman]

I am in no way trying to be a jerk but I am super curious what you have going on in that picture, that laticrete mat is not waterproof? Not sure how that is going to work with a linear drain?...

Good question, and I suppose you caught me... In my install, the drain is just there as an overflow catchall, with a tub behind it. Between the fact that the Strata Mat allowed me to use modified thinset (Ditra requires unmodified thinset), and the porcelain tile with polymer grout, I'm not worried about water getting through the perforations, but then again, this is NOT a shower. Just a surface that sees an occasional splash.

Regardless, I'd go with Kerdi (my next bathroom will likely use Kerdi XL) or just do this again, over using cement board as an underlayment. The reality is that no matter how many flat layers you bond to the surface of your joists, be it a layer of plywood and then durock, or just durock, they don't add to the rigidity of the floor. So when your joists are bouncy, only decoupling the tile layer from them will truly insure against cracking.

 

[cgrutt]

Here are a few pics from a project I did a few years ago. Subfloor was full of mold, replaced with new subfloor, primed with mold control primer followed by Ditra. No kerdi on corners of flooring this project didn't really need it. Tub enclosure is hardi board waterproofed with kerdi and aquadefense. Thinset and grout is all Mapei.

@MEDTECH where abouts in Northern Jersey? I'm in Rockland please let me know if you need any help with anything happy to help if I can.

Subfloor



Ditra



Complete (pending counter top).

 

[mike93lx]

My bath remodel was advantech and ditra heat. Worked out awesome and is exactly what I would do in another remodel. Shower surround was kerdi board and tile. I didn't go up the wall with the ditra to fully waterproof the floor, but thats a great option if you want to really waterproof

 

[MEDTECH]

Here are a few pics from a project I did a few years ago. Subfloor was full of mold, replaced with new subfloor, primed with mold control primer followed by Ditra. No kerdi on corners of flooring this project didn't really need it. Tub enclosure is hardi board waterproofed with kerdi and aquadefense. Thinset and grout is all Mapei.

@MEDTECH where abouts in Northern Jersey? I'm in Rockland please let me know if you need any help with anything happy to help if I can.

Subfloor



Ditra



Complete (pending counter top).

That looks fantastic! And I really appreciate the offer of assistance; I just want to ensure this job goes correctly because I'd hate to re-do it in 10 years due to water damage or a crappy install.

 

[duneslider]

That looks fantastic! And I really appreciate the offer of assistance; I just want to ensure this job goes correctly because I'd hate to re-do it in 10 years due to water damage or a crappy install.

If you do it RIGHT, it doesn't matter what method is used it will turn out good and last forever. I was just trying to get across that just because it is a drop in tub/shower doesn't mean it will be problem free, those get screwed up too. I rented a house for a year with a manufacutered drop in shower that wasn't sealed correctly and it had a molding mess going on under the drop in pan.

I recommend picking what you want, then following all the manufacturers guidelines. I sometimes fudge guidelines but I also have enough experience in these areas to know that it will work and be fine.

 

[duneslider]

Good question, and I suppose you caught me... In my install, the drain is just there as an overflow catchall, with a tub behind it. Between the fact that the Strata Mat allowed me to use modified thinset (Ditra requires unmodified thinset), and the porcelain tile with polymer grout, I'm not worried about water getting through the perforations, but then again, this is NOT a shower. Just a surface that sees an occasional splash.

Regardless, I'd go with Kerdi (my next bathroom will likely use Kerdi XL) or just do this again, over using cement board as an underlayment. The reality is that no matter how many flat layers you bond to the surface of your joists, be it a layer of plywood and then durock, or just durock, they don't add to the rigidity of the floor. So when your joists are bouncy, only decoupling the tile layer from them will truly insure against cracking.

I figured the area wasn't that wet, so it wasn't that big of a deal but just wanted it to be clear to future people that laticrete's uncoupling membrane is NOT waterproof like Ditra is. I actually think latricrete had to put the holes in their product due to some patents that are still active with Schluter's product. The ease of use of the uncoupling membranes and the kerdiboard/hydroban board had me abandon cement board more than a decade ago, the slight extra cost is worth every penny in my opinion.

Also, I use modified thinset over and under Ditra and Kerdi all the time. If I can find it, I will use Laticrete 272 unmodified with kerdi it is super nice stuff and works amazing. I have rarely used unmodified with ditra but you still need to be careful with that, there are some that will have issues and some that won't. I can definitely say that Latricrete 253 Gold (usually at tile stores only) is fine, Versabond (found at home depot) is fine, there is also a Mapei modified thinset at Lowes that is fine but is seems mapei is always changing names of stuff so I never know what their current name is.

Going to a what I call super modifieds like Laticrete 254 Platinum can have drying issues under porcelain over ditra, it just takes longer to dry sometimes and frankly is way over kill but I have used it over kerdi with small glass tiles but in those cases, it dries fine. Anyway, way more info than needed but there is zero issue with using SOME modified thinsets being used.

I used Laticrete 253 over and under everthing in my own house and use it for basically everything. It is a great all around tihnset. Also, you can use ANY type of grout over ditra and kerdi, no worries with anything there.

 

[duneslider]

My bath remodel was advantech and ditra heat. Worked out awesome and is exactly what I would do in another remodel. Shower surround was kerdi board and tile. I didn't go up the wall with the ditra to fully waterproof the floor, but thats a great option if you want to really waterproof

I have a bathroom floor very similar to that in my own house. Might be the same tile.

 

[mike93lx]

I have a bathroom floor very similar to that in my own house. Might be the same tile.

It was my first tile project. Starting with a hexagon was probably not wicked smaht, but I was happy with it.

My big miss was undersizing the heater wire thinking that it would spread the heat better... Having my left foot be nice and toasty but my right foot cold while on the can was not awesome. #1stworldproblems

 

[MongoTA]

Even if grout cracks, nothing should leak. Grout and tile are there for looks, not to waterproof.

Holy ****!
Someone who actually knows what he is talking about!
(just in case...that's a compliment)

 

[duneslider]

It was my first tile project. Starting with a hexagon was probably not wicked smaht, but I was happy with it.

My big miss was undersizing the heater wire thinking that it would spread the heat better... Having my left foot be nice and toasty but my right foot cold while on the can was not awesome. #1stworldproblems

You wouldn't think hex tiles would be that much different but they really are more difficult. My BIL was building a cabin/investment property near Yellowstone and he asked if I would help do some tile and then when it was done we could take some trips up there. Anyway, I showed up thinking I would knock out a quick tub surround over the weekend and it was 8" hex tile. It took twice as long and was a huge pain in the ****!
I have always had mixed feelings with floor heat. Its so hard to know what is right, not enough, or too much. I didn't put it in my own house because I didn't want to deal with it and knew my wife would put rugs down no matter what I did.

 

[duneslider]

Holy ****!
Someone who actually knows what he is talking about!
(just in case...that's a compliment)

I have a rewards account for the holiday inn express.