DIN 18534 in renovation waterproofing

Hello everyone,

I had the wall tiles in the bathroom replaced by a tiler. The bathtub remained the old one, only the tiles were renewed. My plumber now pointed out to me that no Elastogum or similar was applied under the tiles (the bathtub can also be used for showering). My tiler said that when replacing tiles where the bathtub is retained (grandfathered protection), this does not have to be done – and if it were necessary, it would be the plumber's responsibility.

Therefore, my question: does DIN 18534 not apply in this case? I want to protect myself legally against the owner.
In a bathroom renovation where, for example, a walk-in shower is installed, sealing must definitely be done. For my specific case, I can't find anything legally binding. Of course, sealing would also be technically useful here, but my concern is only whether it MUST be done.

Thanks in advance for helpful answers

Hello questioner. The topic you asked about is complex – which is probably why no one has answered the question so far. To answer it: Yes, DIN 18534 Part 1 also applies here. Now it actually depends in detail on whether the bathtub is equipped with a (hand) shower or not. If there is a shower in the bathtub, but a partition (or splash guard) in front of it, or if the bathtub does not have a shower, then both the floor and the wall are within the exposure area of class W1-I. This means: moderate exposure without intensification by standing water. DIN 18534-1 stipulates that waterproofing according to the standard becomes necessary in case of (among others) moderate water exposure, thus also for W1-I!! DIN 18534 (from July 2017) now specifies in Part 3 that for the exposure class W1-I the waterproofing type is with polymer dispersions. To not make it too complicated: If, for example, a wall surface is newly built up, in this case above a bathtub, waterproofing with a polymer dispersion must be applied, for example, before (after curing) the tiles are installed! As preparatory work, it must be taken into account that the bathtub of course does not have to be dismantled in order to add a missing waterproofing layer. That would be a bit too much. But! According to current standards, the bathtub edge adjoining the wall surfaces must be sealed with a sealing tape. An elastic sealant, which is often confused, is not a sealant in the sense of the waterproofing standard!! This means: degrease the bathtub edge at the wall, prime it with a suitable primer, and then lay the sealing tape in the liquid adhesive made from, for example, epoxy resin on the bathtub; in the wall area the protruding sealing tape is embedded in the liquid dispersion. Once it has cured, the protruding sealing tape is revised again with the dispersion. The sealing tape thus lies both below and above in the polymer dispersion. Corresponding shaped parts from the sealing tape manufacturer are to be used in the corners. It really is not that simple – as you can see – but the tiler is not right in this case. Rather, he did not comply with the technical rules, the work does not correspond to the state of the art (which he owes you!!) and is therefore defective and requires rectification. If we now think further about what a rectification will look like, I only need the keyword "dismantling." This way you now know what the installer needs to be prepared for. Regards: KlaRa

Thank you very much for this comprehensive response. So I am dealing with an ignorant tiler who gave me poor advice? Only tile laying was commissioned, and that is all he did. So he should have informed me that sealing is mandatory? According to his view, sealing is not necessary in this case – with that, he would actually be professionally unfit.

Well, other aspects might underlie the professional incapacity. If we are talking about ignorance, he apparently did not keep up with the important developments in waterproofing standards. That certainly does not protect him from recourse claims in case of emergency. In my remarks, I assumed that he removed the old tiles and rebuilt the wall surface. Then what I said applies without restriction. Regards: KlaRa

Yes, the issue with the occupational disability was a bit exaggerated. Unfortunately, the gentleman is familiar with the new rules, he just believes that waterproofing is not required for a purely tile replacement. Well - thank you very much for the help - I am currently drafting the notice of defects.