Installed Kerdi-band over Kerdi-board but thinset seems fragile.

[Bonobo]

First timer here..I'm (slowly) installing a Kerdi-Board tub surround and have applied the Kerdi-band using a Premium Plus unmodified thin set that was recommended by the kid at the HD store.

The Kerdi-band seems adhered well enough but after a couple of weeks, the dried squeeze out is still very fragile. It wipes off with a wet sponge and there are lumps of hardened thinset on my drop sheet that can be crumbled easily if I wet them. Again, the Kerdi-band seems well enough adhered but I'm worried that any water getting behind it will loosen it.

I was considering cleaning up the excess squeeze out and sealing the Kerdi-band edges with yet another waterproofing product ($!!!), then using a better quality unmodified thin set for the porcelain tile installation.

Am I worrying too much?

[cx]

Welcome, Paul.

Probably.

What thinset mortar did you use to apply your Kerdi.

[Bonobo]

Thanks for the input. I'm trying to do a proper job but worry that I'm giving in to obsessive/compulsive tendencies.

It was Premium Plus Standard thin set mortar "Exceeds ANSI A118.1 without additives ". It was the only unmodified stocked at my local HD and their sales guy assured me it was the appropriate product for the job.

[cx]

Helps if you'll add a geographic location to your User Profile, Paul, so we'll know you're not shopping in the USofA, eh? We no longer have Premium Plus available down here last time I checked and yes, it is appropriate to your application.

Those very thin sections of thinset mortar that squeeze out of your Kerdi overlaps very likely dried before they had a chance to really start their hydration process, resulting in the sand-like consistency you are observing. The mortar between the Kerdi layers is likely just fine.

If it'll make you more comfortable, I'd recommend you make a test board with some Kerdi and your Premium Plus, wait a full week, and pull it apart. Think you'll find it's bonded quite satisfactorily.

My opinion; worth price charged.

[Bonobo]

Sounds like a sensible plan.

Thanks!

[jadnashua]

What's critical with any mortar, is it must not have dried or skinned over before you embed whatever you're trying to bond with it. Kerdiboard probably wouldn't benefit from it, but other surfaces can really be helped by wiping them with a wet sponge prior to applying the thinset. This helps prevent the surface from absorbing too much moisture, leaving all that's mixed into the thinset to hydrate (cure) the cement which is required for it to gain the designed strength. During the heating season, the humidity levels in a home can be quite low, and any exposed thinset can dry out before it can cure.

It's not confidence inspiring, but thinset really does continue to gain considerable strength over time. Keep in mind, the specs for that are after it has had 28-days to cure. The moisture in the thinset between two waterproof surfaces has the best opportunity to properly cure, and the bond is quite good - IF you give it the proper time. It's strong enough so you can start applying tile immediately, though. Trying to pull it straight off is tough at that stage, but you could easily peel it off the wall if you tried - that sharp angle applies all of the force at a very small line - much different than trying to pull straight off.

[jim_c]

I used the Premium Plus thinset on both my recent Kerdi shower projects.
It seems to have worked as expected. I don't think there are any issues with the product in this application.
If you applied it correctly it is very likely OK.
I used Versa Bond from HD for my tiling and find it to be a satisfactory product also.
But don't be getting too much advice from HD folks - use this site for that!

[Bonobo]

Thanks guys. Glad this forum was around to get me through the initial panic.