Porcelain stoneware bowls, is correction possible?

Hello everyone,

Unfortunately, I had a leaking weld in the PPR pipe of the water supply in my bathroom, causing water damage.
That means laboriously chipping out and sanding the old tiles and adhesive, resealing with PCI Lastogum, installing the drain channel, and now I am currently cutting/laying tiles, where we have already reached the problem area. To begin with, I am not a tiler, I would have really preferred to hand this over to a professional, but the quotes for the 4 wall + 2 floor tiles were really outrageous (despite having the material Feinsteinzeug + PCI Nanolight) ~ 2k euros.
So I have to do it myself because unfortunately, I don’t have a money tree yet...

The project has gone well so far, I have cut and deburred the tiles and roughly laid them out.

Unfortunately, I then noticed that the Feinsteinzeug, despite being first choice and calibrated, forms a bulge upwards in the middle of about 4mm...

I tried to capture that visually for you.

My question now is, is there a way to compensate for this bulge in the tile? When I apply pressure to the middle of the tile, it pushes down... does it work in practice if I press the tile down while the adhesive dries, will it stay permanently straight or is it just a matter of time before it warps upwards again due to internal stress?

I would really be grateful for a tip... I bought 6 tiles from different batches and all have this cupping... unfortunately these tiles are elsewhere in the apartment, so I can’t just swap them for others or it would look bad...

Best regards.

For your information: the tiles are only roughly laid and the Lastogum you see is the new one; underneath there is another layer of Lastogum which continues under the angle profiles.

Hello questioner. By "Schüsselung" we understand a buckling, a convex deformation. This occurs either in the middle of the material or in the edge areas. In the case of ceramic tiles, this deformation would already be fixed in the tile itself, thus inherently part of this/those tile(s) as a material property, integrated during manufacturing. Such a convex deformation cannot be corrected if it is solely and exclusively due to the tile itself. By applying a surface load in the not yet cured state of the tile adhesive, we only achieve that the tile lies deeper with a central (convex) deformation, but the edge areas then sink so much that water would remain standing in them. I suspect that the problem was described incorrectly. Formulated generally: In practice, it can certainly happen that one has to hold the freshly glued tile in the later desired position by a load until the adhesive cures. But this is not the normal case. Unless the elastic underlay (sealing) was applied in a noticeably compressible thickness. Which can be excluded for Lastogum (recommended minimum dry film thickness of 2 x 0.5mm = 1.0mm). ------------------ Regards: KlaRa

Thank you for the quick response.

If I understand correctly, I have to live with the deformation of the tile? It really looks pretty bad, I would have really liked to achieve a straight/nice edge on the (expensive) drain channel.. once again you can see how far promotional leaflets and reality differ from each other.

Is the channel installed straight? There is really a lot of overhang.. Try pulling it down with the [Verlegsystem]. ;)

One must also see the following: the photograph is actually meaningless (Sorry). Just place a tile on the usable side, place a flat but straight piece of metal on top, and position a ruler in the middle so that any possible surface deformation (and its size) can be detected. Then do the same, but with the backside down and the metal piece on the usable side. This way it becomes clear what is actually wrong with the tile. The associated texts, in any case, do not allow any conclusions about the ACTUAL condition. Regards: KlaRa

Is the channel installed straight? There’s really a lot of overhang.. Try pulling it down with the laying system. ;)

Yes, it is fully bedded in mortar; I paid the utmost attention to that since it cost 400 euros -.- (ESS Drain Compact) The leveling system doesn’t work like that because I don’t have a point on the channel where the leveling eyes could grip. I thought about it already, but it’s basically the same if I put something heavy on top of the channel and let the adhesive cure (solid iron or something similar..)

But I want to know if this can be justified or if it’s to be expected that the tile will eventually bend upwards again and detach from the adhesive.

One must also see the following: the photograph is actually meaningless (sorry). Just lay a tile on the usage side, place a flat but straight metal piece over it, and put a ruler in the middle so that any surface deformation (and its size) can be recognized. Then do the same, but with the back side down and the metal piece on the usage side. That way you can see what is really going on with the tile. The accompanying texts at any rate don’t allow any conclusions about the current state. Regards: KlaRa

I tried to capture it visually, unfortunately not possible.. when I place a 60 cm spirit level in the middle of the tile and then tap the spirit level on the right or left, it wobbles back and forth.. that is the mentioned warping.. at the most central point it is a 3-4 mm “elevation”.

It just looks bad as can be seen in the picture, since I don’t get a straight edge over the entire surface of the channel..