Bathroom Remodel - Down to the studs and joists

[HouseOfJoe]

So I did my mud bed tonight. First time but I think I did OK. Used Mapei 4 to 1. How long should I let it dry/cure before I Kerdi it? The data sheet is pretty vague on that point!

[cx]

Tile industry considers a mortar bed to be "cured" for purpose of setting tile (or, presumably a membrane) over it after 20 hours, but they prefer more time if available.

While I can say for sure what's in that 4 to 1 pre-bagged mortar, if it's actually mostly sand and cement as advertised, the 20 hours should be a good minimum. I generally determine that time frame by judging the surface of the mortar and what I plan to put over it. Do I need to walk on it? Do I need to kneel on it? Am I gonna tile over it? Am I gonna install a sheet membrane over it? Etc.

My opinion; worth price charged.

[ss3964spd]

I used that 4:1 Mapei mix for my corner benches, Joe, it gets pretty hard. I'd let it dry for a day then have at it.

[HouseOfJoe]

So I put the Kerdi membrane down on the pan this afternoon and Kerdi banded the perimeter. What’s the minimum time I should let it dry before a flood test? And will running a fan in the bathroom make much difference?

[ss3964spd]

I don't know, Joe, and I can't remember how long I let mine cure before my flood test. I likely gave mine a week.

A fan might accelerate the curing time along the edges but probably won't do much for the mortar under the membrane.

But here a thread that suggests you can test after 24 hours, post #2. https://www.johnbridge.com/vbulletin...20flood%20test.

[cx]

Joe, I believe the manufacturer recommends a minimum of 24 hours before a flood test if you used an un-modified thinset mortar. Longer might be better.

Can't agree with Dan on the fan speeding up the curing time. The fan might speed the drying, which you really don't want at all, you want the mortar to cure and it can't do that if it's prematurely dried. I recommend against the use of the fan.

My opinion; worth price charged.

[HouseOfJoe]

Oops. Well I was running a fan under the thought process of “can’t hurt, might help” for the last 18 hours but I just turned it off!

Per the previous discussion on this thread I’m using a modified thinset (versabond). Between discussions here and Sal Diblasi’s recommendations in his videos I had decided to give it 24 hours. I guess maybe now I’ll give it 48.

So much for my promise to Mrs Joe that the shower floor ought to be tiled by the end of this weekend! Another deadline target bites the dust! LOL!

[ss3964spd]

Deadlines - so over rated.

I wasn't actually suggesting fanning the mortar, was only offering an observation. While the mortar at, and maybe just a bit under the exposed edges would dry faster with the air movement I believe the mortar under the membrane and unexposed to the air movement will be largely unaffected. Would the accelerated drying at the edges cause the edges to lift or otherwise compromise the seal? I dunno.

[HouseOfJoe]

No worries, Dan, I’m not holding you responsible for my decision to use a fan. LOL! I had the same thought that the air movement isn’t going to do anything to the thinset under the Kerdi. Only the edges would be affected and thus far I haven’t seen any indication that the edges are peeling up at all so I’m sure it will be fine.

I’ll start my water test tomorrow night which will be 48 hours from when it was installed and even if I’m not at 100% in my application of the Schluter system, I’m confident I’m at a solid 95% plus, and I bet that’s good enough.

[ss3964spd]

I don't recall how long I ran my flood test, Joe, but it was a minimum of 48 hours. I think like pretty much any first timer I was super nervous even though I was also super careful with my installation. I do remember checking it every 15 minutes for the first few hours then, having more confidence, checking it only every 30 minutes. . Not a good night's sleep the first night.

[HouseOfJoe]

Schluter says not to run the Ditra Heat wire under the vanity, but I'm assuming they mean one that actually sits directly on the floor.

If my vanity is on legs (~ 3 inches ish) I can use the space under it for any excess wire I have, can't I?

[ss3964spd]

Exactly as I did, Joe.

[HouseOfJoe]

Thanks, Dan. Kind of figured, but always safer to check!

Another question for the group. I've been using modified thinset (Versabond) everywhere so far but in reading the spec sheet on the Ditra their argument for using unmodified kind of makes sense.

Anyway, is this just one more situation where Schluter doesn't want to have to test every modified thinset out there, but everybody knows that Versabond is going to work fine? Or for this particular application would I be wise to go ahead and use unmodified?

[BIGPHIL]

Originally Posted by joe

Anyway, is this just one more situation where Schluter doesn't want to have to test every modified thinset out there, but everybody knows that Versabond is going to work fine? Or for this particular application would I be wise to go ahead and use unmodified?

Joe,
If your talking about setting the tile on the Ditra, then yes... consensus is that Versabond will work just fine and many people set tile over Ditra with it without issue. If you're worried about it, go grab a bag of Schluter All-Set as it's one of two Schluter approved modified mortars for setting tile over Ditra.

[ss3964spd]

It's a catch 22, Joe, if you're setting porcelain. While Schluter wants unmodified atop Ditra a modified is generally recommended for setting porcelain. To add to the confusion, Schluter does offer their own thinset mortar, a modified, approved for use atop Ditra. Probably has something to do with the type of modifiers used.

I used Versabond. I did have to remove a floor tile a few days after it had been set and the VB under it was virtually completely cured. My tiles have been in place for over 1.5 years.