tiled and heated shower

[GCloud]

Hello everyone

My name is Grant. I've just stumbled across this forum and there's tons of great information here!
I'm about to undergo my first tiled shower and I've got a few (many actually) questions. I've looked at the ontariotile site and its been a lot of help, but I'm still a bit confused.


I'm replacing a prefab plastic shower base with a mortar base and center drain. The final shower will be about 3'X5' with full glass on two curbs extending to the walls...tile everywhere.

I'm planning on using kerdi on the floor and on top of concrete backerboard for the walls (is this the way to go?) and want to install a wire heating system under the base tile.

A couple questions:

I understand that without the heating system I've got to make a preslope...then install kerdi waterproofing...then make the mortar bed and install tiles, no? Where does the installation of the wires come into play? Do I follow the preslope-kerdi-mortar base procedure and then install the heating wires embedded in a later of thinset and then tile on top of this layer? Seems like a whole lot of layers!

How do I ensure water on the walls doesn't seep through the tiles and then outside the glass enclosure? Is this just a natural weak point? I can't imagine a whole lot of water spraying the joint where the glass meets the wall, but I feel like I should be able to spray water anywhere in the enclosure and have a guaranteed water tight seal.

I've also noticed on a number of sites that kerdi is applied to the walls and then the base. Is it not important to have the higher layers overlapping the lower layers?


I'm feeling like this is going to be a humbling experience! Any help would be much appreciated!!

Cheers
Grant

 

[Jadnashua]

No, you're confusing the Kerdi membrane with a conventional shower construction. When using Kerdi, you only have a one layer sloped bed. Then the Kerdi, then the tile. You need their special drain to bond the membrane to. Unless you are building a commercial steam shower, the preferred medium on the walls is plain drywall. Kerdi is totally waterproof, and therefore, the drywall stays dry. You need to read the Kerdi handbook, and view the installation instruction videos on www.schluter.com. Another good place for help is www.johnbridge.com. The advantage of any surface membrane systtem is that the main structure of the shower is totally isolated from ever getting wet. Do it wrong, and you trap moisture, though. Understanding the methodology and following through is crucial to any shower build, but maybe more so when using a surface membrane since it assumes the stuff underneath will never get wet. It won't, if you do it right.

 

[Sponsor]

 

[Jadnashua]

Schluter makes some preformed, foam trays. If they happen to be the right size, or close (they can be trimmed), you normally could use one of them...very fast, very easy. But, the membrane sticks to a mortar sloped bed just fine, and you can then build any size, configuration, etc. pan you want out of that stuff for less money (unless you are paying labor), and it will be just the right size. You'd probably have problems using heating under the foam tray, but it should not matter on the mortar base IF you installed it underneath the mortar. Probably isn't a good idea directly under the Kerdi. I'd have to scan the installation manual.

For a first-timer, the biggest issue (and that's pretty much been updated on the new drain components) was the folded corners when installing the Kerdi. The multiple layers could end up with a bigger buildup in those corners (depends on your technique). But, the new drains come with preformed corners rather than the old folded ones, and are therefor much less likely to create that sort of problem. Those corners come with the drain, but are also available as a separate item. The biggest issue with Kerdi installation is getting the thinset properly mixed, then getting the material up quick enough before it skins over. It's sort of like putting up wallpaper, but you have more leaway on the seams - they don't need to line up perfectly. Assuming you use the Kerdi-band to waterproof the seam, as long as there's at least a 2" overlap, you are fine. Some people put the tape on the seam area first, then install the sheets, some put the tape on after. I think it's easier to do the tape first as the thicker sheet tends to even out the overlap. Don't try to wrap it around corners the first time you use it...more seams just means more band, but not a less waterproof system.

Because Kerdi is essentially waterproof, and some tiles are as well (or nearly so), a modified thinset can take a huge amount of time to dry and cure. For this reason, under most circumstances, Schluter does not recommend a modified thinset. FYI, the two biggest differences between a modified thinset and an unmodified one are: how sticky they are, and their ultimate strength. But, some of it comes down to how much is enough? A good unmodified thinset has a cured shear strength of over 250# per square inch. A modified might be in the order of 100# more. Another difference, that often isn't an issue, especially in a shower, is that a modified is a 'little' flexible once cured. Not much, but it is. So, in most cases, a modified is overkill - many people like overkill. Schluter does allow a fast setting modified over Kerdi and Ditra (if you ask, they'll tell you what). And, admit if you can wait between setting and grouting, you might get away with a lightly modified thinset. The reason for this is that the only exit path for any moisture required for drying the modifiers is through the grout joints, and if they are filled, it either may not happen, or the tile might have been disturbed before it occured, and the bond compromised. You DON'T want to use a modified over a waterproof membrane, then do something like walk on it before it has a chance to dry and cure, as you could break the bond. If you are willing to wait (often they like a week or more if you can stand it), then a modified will work. You need special 'dispensation' if you want a warranty. The quick setting stuff gets strong enough, quick enough, where they aren't worried, but trying to ensure a compatible one is used is why there is a general 'use a good unmodified' requirement.

What happens with a modified thinset is that the plasticisers, after wetting and mixed the first time, get mixed around the cement particles and totally coat them after you do the remix after the slaking (resting) period. This is why it is so critical to wait the specified time and remix a modified thinset before use. The strength, bonding ability, and consistency can change RADICALLY if the exact procedure and timing is not followed. It is not quite as big a problem with an unmodified, but if it is not mixed thoroughly, you can have similar problems. It is very important not to put too much water into any thinset. The consistency of a modified will change as those dry plasticizers absorb some of it during the resting period. So, doing it by 'eye', is not a very good idea...measure!

 

[Geniescience]

Other Moisture Barriers Besides Kerdi for Shower.
If there ever was a subject for a discussion, this would be its title.
Then, the OP would write: " I have read most of the posts here on Kerdi and that definitely seems the way to go, but just wondering if ..."


On the internet, Kerdi is definitely the way it often seems to go.
In reality, not on the internet, things are "real".
The Kerdi manufacturer has invested in making internet advisors into Kerdi users.
Free courses, free product, advertising dollars, and more.
They can even create profiles of people asking in a way that is mistaken so that good people can rush in and correct them.
Then, these internet queries can all end up "deciding" to use Kerdi, no matter how the thread started out. I've seen this happen hundreds of times at one Kerdi-sponsored advisor site.

I believe K has caught the fancy of people who like to keyboard, and that is why it is all over the internet. In the real world it is not "the thing, the way, the one". There are many other products and other ways of doing things. Buy Wedi if you want a high cost product that reduces labor costs instead of increasing them.

There are many other products and other ways of doing things, not just the one that keeps coming up on internet discussion forums. In the real world, the one you asked about is one of many, and not "the thing, the way, the one".

Many people) will vouch for the many liquid membranes there are out there. They are great. Think of rubber, not a thin and brittle coat of paint. Believe me when I tell you that they are good. In the real world, these products do get manufactured and delivered, bought and sold, installed and warranteed. So just be aware that all of us often talk about one product only. It's only one out of many good products. They are all good. None are bad.

There are liquid membranes that you paint, roller, trowel on.
There are board membranes that you screw on and then seal the seams of (and the screw holes) with a caulk.
There are sheet membranes that you unroll, and you need to seal the sheet overlap.

"Is Kerdi needed?" is another good topic for a discussion.

Hope this helps you with one of your main questions.
I'll post another day about the floor heat.

 

[GCloud]

thanks everyone for the tips!

watched the kerdi video...seems easy enough.

John...to answer your questions:

Are you a serious DIYer and do you have any prior tile setting expeirence?

Yes...I'm a carpenter so I've got quite a bit of general experience, however this is my first shower. I've done tiling here and there, but never with slate, which is what I'm planning on.

Is your shower going to be a steam shower? If not then you may find working with a liquid waterproofing system easier.

Its not going to be a steam shower.


Are you heating the entire room with cable heat or a heating pad? Which system have you selected - many are not improved for installations in wet zones.


Yes...this was the plan. Flextherm is the name of the product and the salesperson advises it is okay for under Kerdi. He suggested installing it below the mortar base. He also advised that it is one of the only systems that can be in a 'wet' and dry zone controlled by one thermostat.


What typ of tile are you working with?

I'm working with slate.

Are you going to install a simple point drain, a kerdi point drain or a linear channel drain?

Kerdi Point Drain


What size plumbing lines do you have? Are you doing the plumbing and are you pulling permits.

I'll have to check later for plumming line size. And can I just avoid the permit question ?


I live and work here in North Vancouver and can help you out right here.


Awesome! I'll fire you a pm.



If you don't mind sharing your renovations upload your pictures here. If you create an account you can mouse over your picture and copy the file info (bottom one works here) and past the picture into this thread.

Will do.

Thanks again!

Grant

 

[GCloud]

Hello again.

So...what should have been a straightforward shower install has revealed itself as something totally different.

Water damage was bad to say the least. Pics to follow.

Enough to say that after pulling out old prefab showed bed, lino, concrete slab with radiant heating, I was able to poke holes in the plywood subfloor with 2 fingers in numerous places. Shower pony wall consisted of drywall that, when torn out, could easily be 'broken' (more like disintegrated) into a smearable mush, and pure black 2x4's that I could very literally wring water out of. Luckily, after all that the water seems to have had little effect on the supporting members. An inspection of the bottom floor framing is yet to come, and I'm a little nervous, but one project at a time.

Bummer because the house was built only 20 some odd years ago.

But along with everything else I've seen in this house much is not to code. Studs are not on centers and shower had nothing but drywall-thinset-tile-grout to act as waterproofing.

Needless to say there was some demolition.

I'll post some pics when I can, but I just wanted to update and throw it out there that the new mortar bed lined with kerdi is 27 hours into a flood test with no sign of water loss!

I gotta say...I've received extraordinarily generous and knowledgeable support from our own John Whipple. He's all over this and other forums always offering help and reviewing products and methods. We met at his beautiful house in North Vancouver and he gave me the royal tour, a mind-blowing list of tips, and he even donated some supplies to help in the cause. John, I can't wait to see your completed kitchen with all the bells and whistles!!



Cheers
Grant

 

[Jimbo]

Sounds like a job for our main man Mike Holmes. His homies also like the Kerdi.

 

[LLigetfa]

I don't want to turn this into a Kerdi debate. I recently renovated my bathroom and used Kerdi. I disagree with some of the advice given here. First off, I would never use regular drywall in the shower area, nor would I use the blue stuff. I went with DUROCK.

The only challenge with Kerdi is the use of modified thinset when using a product like glass tile, that insists on it. Well... that and you need to allow for the additional thickness on the overlaps. I cut mine a little close around a cubby and ended up having to nip a little off the back of the metal Schluter edge in spots. Better to allow for it on the backer board so it sits flush after all of the overlaps. Also had to shave a tiny bit off the back of a few tiles in spots.

I have to question though, why bother with electric floor heat inside the shower? I mean, the hot water will warm up the tile in seconds anyway. If it is used as a single zone both in and out of the shower, the K factor of the extra thickness of the mortar base would likely give different results inside the shower.

 

[Jadnashua]

I don't want to turn this into a Kerdi debate. I recently renovated my bathroom and used Kerdi. I disagree with some of the advice given here. First off, I would never use regular drywall in the shower area, nor would I use the blue stuff. I went with DUROCK.

Getting minimal buildup in corners takes a little skill, the preformed corners, and the right thinset, but it can be done. The preformed corners are thinner than just overlapping the Kerdi, or making your own with Kerdiband. I was in a class where they were teaching Kerdi installation. They had a paper cardboard box covered with thinset and Kerdi (inside only) that had been in use as an icebox for drinks. It had been there for months and by the end of the day was full of icewater. The cardboard was totally intact, with no signs of water damage. Kerdi works just fine over drywall. If you do install it over a cbu, it will work fine, too, but you need to be more careful about the cbu sucking moisture out of the thinset prematurely verses regular drywall. Drywall is less expensive, is readily available in larger sizes (fewer joints), lighter, and easier to install. Use cbu if you feel you must, but it is a personal perspective, not held by the manufacturer that gives the warranty - it will work over either.

 

[LLigetfa]

Jim,
All valid points. I did use the thinner preformed corners but doing something like a cubby where you have both inside and outside corners, plus the wall, plus the cubby, the thickness can sneak up on you. I did mock up everything first using building paper origami to get my folds and overlaps worked out.

Here's a pic of the cubby. The green masking tape is temporary.

 

[GCloud]

Yes..I also avoided the use of drywall. Not because the manufacturer doesn't suggest it, but because after seeming the ease at which it was compromised in the previous shower I thought it would be best to go with something a little more water resistant just in case. It was suggested I use greenE board which I used.

I used a combination of thinset and kerdi Fix to install the kerdi. Kerdifix was used on the most important joints. It was not cheap. Around 20 bucks, but it's straight forward, easy to use (not at all easy to get off the hands...latex gloves Strongly recommended), and the tube keeps overnight which thinset doesn't.

I do have a concern about the kerdi and it's natural tendency to wick water. I know people say it doesn't and that water miraculously beads on it but that hasn't proved to last.

In fact, and I'll post pics in a new thread, I've started a kerdi wicking test and after one hour it's failing miserably.

I've suspended a strip of kerdi over a cup of water and marked dots on the kerdi with a water soluble ink. Tue dots are located at roughly 3/8ths intervals. In one hour, the lowest dot is gone. Completely. The only possible way for this to have happened is that water has been wicked up the strip. I give it a few more hours before the top dots (at 1 1/2") are gone.

Having discovered this, I'm going to coat everything with something like hydroban or redguard. I just don't trust that water isn't going to wick into my joints and over time (years if I'm lucky) degrade joints and render my work useless.

But as I said, I'll start a new thread to discuss this wicking issue and post some of the early experiment pics there. And pics to come of the current project.

Cheers
Grant

 

[GCloud]

oh...and the heated flooring in the shower bed. Its such a small area and the additional cost to have a nice heat everywhere in the room on the feet was just a nice thought. I've chosen however to not do this step out of simplicity and time. That said, I would definitely like to have this feature. Why not? my shower area is about 12 square feet so the cost is minimal. For Flextherm, which I understand to be one of the only, if not THE only, systems that can be installed in a dry and wet area off one thermostat, the cost of upgrading from one unit to a unit with 12 extra square feet is about 30 bucks. An extra layer of thinset is what?...5-10 bucks? I've had the opportunity to test out a bathroom with full coverage heated floors and its great! Warm feet all the time

Grant

 

[LLigetfa]

The wicking might just be the fleece on the surface. A better test would be to take a sheet and pleat the corners to fit in a cardboard box and then fill it with water.

 

[GCloud]

LLegitfa, I agree this would be a good test. I'm going to do this one next.

Having said this, I have seen this box test you're suggesting in action. I'd have to defer to the tester for details, but according to him his box has been wicking and loosing water. I saw the box. The kerdi was saturated above water level, and the wood frame was wet. Surely this wouldn't happen with something like a rubber liner...something like a pond liner. I gather this is the type of material used traditionally.

I guess I wonder if the wicking can happen between a joint made with thinset. Also I'm concerned with wicking happening under the glass on the curb, and at the wall where the glass meets the wall. Maybe I'm barking up the wrong tree, but I feel like my shower should be 100% waterproof everywhere with no seeping due to wicking.

Check the post regarding wicking for more test results.

Cheers
Grant