Hardie Hydrodefense - redguard, kerdi, both?

[Determinedkvb]

Diy shower/bath enclosure, and I'm doing niches that will be behind the cabinet side in the kitchen wall. I am trying do do what makes the most sense to waterproof all corners. I've read/watched enough to confuse myself.

Kerdi-band has been suggested as a good product and this is what I was planning to use. The band to be just seems like a better solution than a coating.

Hardie is saying to use modified thinset for joints and tile.
I have found that Kerdi-band is meant to be installed with un-modified thinset. it seems that modified thinset can also be used, but this takes longer to dry.
I thought I was supposed to apply the Kerdi-band with Kerdi-fix (confusion comes from seeing Wedi install video).

I did find Mapei Mapeguard and was not surprised that it is intended for modified thinset.


This leads me to believe that The Kerdi-band can also be adhered with modified thinset.

Or should I just use the un-modified against Hardie's instructions?
Or return the Kerdi-band and just do Redgard?


Thoughts?

 

[wwhitney]

A few points:

Plain hardiebacker is not waterproof. The Hydrodefense version presumably has a surface coating applied. For a shower surround, you'd want to waterproof all the joints and all the screw penetrations, anywhere the surface coating is not continuous.

Schluter's prohibition on using modified thinset with Kerdi is based on the fact that some modifiers rely on drying (evaporation) to cure, and as Kerdi is nonporous, they could take weeks or months to cure under Kerdi. Schluter actually has a modified thinset they sell that doesn't have this problem. Or Versabond is known to work fine. Most modified thinsets are fine, but generically there's no guarantee.

So you'll need to reinforce the joints with the proper mesh tape per Hardie's instructions, then apply waterproofing to the joints and the screws. For the joints you could use Kerdiband. For the screws you could use little squares of Kerdiband, or you could borrow a technique from the Goboard instructions and thoroughly "spackle" each screw dimple with a sealant. E.g. Kerdifix.

Cheers, Wayne

 

[Sponsor]

 

[Determinedkvb]

I got the Hydrodefense because I did not want to have to "paint" Redgard everywhere (how much do I need, etc). I had the thought that I would put "squares" at the screws. I am getting the Kerdi-fix to use at the edge of the board where it meets the tub, etc - so I need that stuff anyway.

Schluter Systems All-Set 50-lb White Thinset Tile Mortar - $36
VersaBond 50 lb. White Fortified Thinset Mortar - $16

All above understood.

Confusion: "So you'll need to reinforce the joints with the proper mesh tape per Hardie's instructions, then apply waterproofing to the joints and the screws."

I had read that Kerdi-band could be used as the "tape." This may have also been referring to a complete Kerdi membrane over cement-board.

If I'm doing mesh tape and then Kerdi-band (each with thinset), why wouldn't I do them both at the same time

 

[wwhitney]

It is a reasonable point that if the joint has Kerdiband over it, that should reinforce the joint plenty, so the manufacturer's specified mesh tape would be redundant. It's just a question of how much you want to deviate from the manufacturer's instructions. Skipping the mesh tape would give you a flatter result, which would be useful.

How are you going to treat the Hardiebacker/tub flange junction?

Cheers, Wayne

 

[Determinedkvb]

The Cement board is installed (on the outside wall - so far) over the tub flange 1/4 inch above tub ledge. I put silicone on the inside of the CB where it rests against the flange.
The 1/4 inch gap will be filled with Kerdi-fix.

The other reason for "needing" the Kerdi-band is the window. Kerdi-band across wood/cement-board transition.

 

[wwhitney]

So you furred out the exterior wall to let the hardiebacker hang down straight over the tub flange? That's a good detail.

Wood windows in showers are problematic, a PVC, fiberglass, or composite fixed window would be a better choice.

Cheers, Wayne

 

[Jeff H Young]

the ends look like theyll be furred . where the window is usually the tub slams up against that wall but perhaps was a joist or structuralreason to fur wall out.
Window location looks undeseriable , as a plumber no concern of mine. but as a builder or homeowner, I think it needs a long look

 

[Determinedkvb]

Yes, the wall was furred out. This also allowed me to shim the furring to get the wall flat. I am bringing the sides in as well to overlap the flange.
I am still working on this.

The tub was centered. This actually took the showerhead a tiny bit further from the window. It is really only 1 inch on either side

Yes, the window location is problematic. It is a vinyl window set in the old wood frame - there is aluminum siding outside. (picture won't load - I"ll try later with a before and after)

Not much I can do except waterproof as best I can and have a window curtain. This bathroom window is basically the only view of the yard.

You should have seen the bathroom before this. The whole house is a problem. I was advised to burn it down (not on this forum - LOL).


Previous tub location.

I will be trimming the window with PVC prior to installing the tile. I have to get this done to figure out how the tile at window and niche is going to work out. I might have to adjust the height of the niche.

I'm going to get the Versabond. Plan is to use the Kerdi-band at all joints and transitions.
I appreciate the help.

 

[wwhitney]

So if it's a PVC insert window in the original wood frame, it should have a narrow PVC frame. The thing to do is to extend the waterproofing layer all the way to the PVC frame and adhere it to the PVC. E.g. with Kerdiband and Kerdifix to the PVC frame. And then to trim out the window with suitable materials without puncturing the waterproofing.

Cheers, Wayne

 

[Jadnashua]

At the tub/wall junction, I'd use a band of KerdiBand, bond it to the tub surface with KerdiFix, and the wall with thinset. As long as the band ends up covered by your tile, no problem. You don't need to fill the gap with silicone. If you decide you want to, use some foam backer rod. When a slug of caulk ends up square, when it tries to stretch through either thermal or weight making things move, it tends to pull off the ends. If you use a foam backer rod, it forces the shape of the caulk into an hourglass shape, and the thinner section stretches, putting much less stress on the ends, keeping it intact rather than separating from them and leaving a gap.

To avoid any visible caulk that will eventually need to be replaced, you might consider using a profile made for this purpose. They come in various colors and thicknesses to accommodate various tile thicknesses and shades. The Dilex-EKE also has a pocket on one side that helps to hide any tile cuts and the visible part helps to present a nice, straight line.

 

[Determinedkvb]

OK. I am planning to treat all joints with Versabond and Kerdi-band. I am planning to bond the Kerdi-band directly to the window with the Kerdi-fix across to the cementboard.

How to trim out the window is now in question because with KB right at the windowframe, that means I could have tile there or any other "suitable materials" rather than a PVC trim. I'll have to get some work done before I need to get into the options I have. I would need to post drawings as well to properly present ideas, etc.

In the meantime, if I am taking the KB down to the tub with thinset and Kerdi-fix ("You don't need to fill the gap with silicone") are you saying that I I would not have to silicone between tub and tile? Grout between tile and tub - or a gap? I realize this is a whole other point of contention for many.

I would love to avoid caulk at the tiles, because I just don't like caulk, but also because I ran into a guy (from a tile family of multiple generations) who said "If I was to give you just one bit of advice it would be Don't caulk your tile.

 

[wwhitney]

In the meantime, if I am taking the KB down to the tub with thinset and Kerdi-fix ("You don't need to fill the gap with silicone") are you saying that I I would not have to silicone between tub and tile?

No, he's saying that if Kerdiband is Kerdifixed to your tub, that's your waterproofing layer to tub connection, and it's better than the silicone joint between cement board and tub that is commonly shown. So the silicone joint behind the Kerdiband would be superfluous, but it wouldn't hurt.

Then the choice of filler in the finish layer between the tile and the tub is primarily aesthetic and maintenance driven, it's not part of the waterproofing layer. Caulk is the industry standard, as it can move a little to accommodate the joint between dissimilar materials. But you could use grout if you want. Caulk will eventually mildew on the surface and need replacing. Grout will eventually crack and mildew in the cracks, perhaps requiring replacement. I don't know of a bulletproof solution.

Cheers, Wayne

 

[Jadnashua]

Industry standards call for movement accommodation between changes of plane and materials, so between the tub and the surround walls, you need something that is resilient, not something rigid.

 

[Determinedkvb]

I'm not sure that I like the Kerdi-band so much. The window is the main reason for needing the KB, but I'm not sure I like it for horizontal joints.
The thinset was a little bit thick when I started (mixed 5lbs). I read that I was supposed to go for 'peanut-butter" consistency. I did the long joint first. I doubled it because my screw positions were a bit wide of the joint.

I added a couple of splashes of water before continuing the rest of the joints. I mixed the last splash with my hand. It felt smooth and was sticking to my finger when I touched it, but it just felt a bit thick the whole time. I decided to leave it alone, because it was oozing out from under the KB without too much pressure and when I pulled back a few corners it came up wet and would stick when pressed back down with the trowel.

I'm used to a drywall knife, but I did use a zigzag toothed trowel to control mortar thickness - just a bit awkward for me.

Kerdi-fix onto the window and inside of wood frame. Kerdi-band pressed down with fingers then a small putty knife and evened out for 3/8" lap on window. Came back quickly with mineral spirits and paper-towel to clean up the window. Mortar on wall and front side of wood frame. Carefully pressed out flat with the trowel while pressing the KB against the wood frame with left hand. I did not have any problems with the KB pulling away from where it had been glued first.

There is some overlapping at the inside corners and then some patches. Except for the top inside corner patches, Kerdi-band to Kerdi-band overlaps were all done with mortar. Could have been better but it there is plenty of KB, glue and mortar at the bottom corners of the window.

The idea here is that the windowsill will be caulked and there really shouldn't be any water getting under it. The windowsill will likely be set in mortar unless I'm advised to put gobs of Kerdi-fix under it.

My question at this point is: If I wait 24 hours and start pulling on a corner of the Kerdi-band at the left side of the horizontal joint and the Kerdi-band starts coming up - what should I do? Leave it alone? Should I even try picking at one of the corners, or just let it be and move on?

As far as the window trim goes, if I am using PVC should I just be gluing it into place with the Kerdi-fix?
I'm pretty sure of how I will trim out the window. That's the next step. I'll post drawings.

Thank you all for the help.



Edit: I did test the corner to the left (just 1/4") and could hear the fleece tearing. So, KB is bonded.
All screw holes on the bottom section of cement board will be covered with vertical strips of band. Upper section probably just Kerdi-fix "spackle."

 

[Jadnashua]

24-hours later, you'll fairly easily pull apart a Kerdi seam, but that's long enough to do a flood test if it were on the pan. One needs to understand how cement cures...it doesn't need to dry, as water is what is needed to cure. Curing is a chemical process, not drying. During curing of cement based products, the water is literally incorporated into the matrix of the material...it becomes a different thing. Once cured, wetting it won't cause it to revert back...it takes heat, very high heat to break the chemical bonds and drive the water out. What happens during the curing process is that the cement literally grows crystalline spikes that interlock, poke into minor imperfections and around the fleece. Keep in mind that with any cement based product, it is rated strength is based on 28-days of curing...within 24-hours, not all that much has occurred, and it WILL get significantly stronger over time. In reality, cement continues to get stronger over a much longer timeframe unless something else is going on to mess with it.

The reason why they want an unmodified thinset is that SOME modifiers need to dry in order to become stable. Certainly, that's not all of them, but for the casual user, it takes some dedicated sleuthing to find out if the one you want to use is actually suitable. TO make this easier, if you insist on a modified thinset, Schluter does make one. It can take literally months for a modified thinset to dry out underneath an impervious tile over an impervious membrane like Kerdi, and if it is one that needs to be dry to become stable, that can lead to failures. There are other modified thinsets out there that work, but you need to know what to look for to make that determination.

 

[Determinedkvb]

I went with the Versabond. Most of what I applied appears to be at what I imagine is an acceptable thickness. Areas that were thicker around the outside of the window frame have all hardened under the Kerdi-band.

Before I start the tile (probably large format) I'll double check that I'm using a mortar that is appropriate.

I think I am doing OK. This type of job is just a bit nerve wracking for me. I've built plenty, but the stakes here are higher.
That picture above shows that I am keenly aware of how bad water can make things.
I'll say that some of my questions come about as a result of being nervous and also not having done this type of work before.
All I can do is participate by showing that I'm listening to the advice and trying to do a good job.

 

[Jadnashua]

FWIW, Versabond will work when setting onto Kerdi. The modified mortars that don't, generally contain a form of latex. To find out what modifier is used, you have to find and understand the material data safety sheet, not something everyone can or is willing to do. Schluter knows that a quality unmodified mortar will work, and its certification test was done with that. They know the modified version they also sell will work. They do not want to or be held accountable to other manufacturers that they have no control over to say you can also use X because tomorrow, they may change it to a 'new, improved' version, that may not, and the consumer just looks at the brand name and model.

The weakest point in the tile/Kerdi bond is the strength of the fleece which is required to be NLT 50psi, and is generally at least 75psi. The bond strength of a quality unmodified thinset to a tile is usually in the 250psi range and a modified mortar can be more...but, take a 12x12" tile at 50psi, that's 12x12x50=7200# to shear it off the wall...and, it's likely more than that. Some people get all bent out of shape about the lack of a modified mortar, but if they really understood, they'd not. This all assumes good workmanship.

 

[Determinedkvb]

My initial problem with figuring out which thinset to use came about because Hardie stated a requirement of modified while Kerdi stated a requirement of unmodified. That puts a DIYer in a tricky spot.

My other problem was the availability of waterproof backer-board. I felt this was a necessary item because the tub butts up to a kitchen wall that will have cabinets and a countertop. And, I can't stop myself from building a niche here.
I of course understand that waterproofing depends on things other than the board - thus my initial question.

I think Hardie products suck up a bit of water which I imagine could cause a problem with unmodified - who knows.

Trying to get information via the internet is a wild goose chase. However, I have come across many of the points that you have mentioned here.
Verification of anything required that I take a chance and ask questions here in this forum - one that popped up repeatedly in my searches about plumbing and everything related to tubs.

Wayne mentioned Versabond - and I double checked the info as best I could.
I bought the Versabond nearby. I was surprised to find the Kerdi thinset later - I resisted the urge to buy it for 3X the price of the Versabond.