Preparations for porcelain stoneware terrace

Hello Thorsten. I only hope that you are slowly recognizing the weaknesses of online surveys. There you receive information, right. But who enters it there, whether expert knowledge is present, and if yes, to what extent, a layperson cannot recognize.

What is important is that you ask yourself questions. For example, why an outdoor terrace requires a frost protection box. You cannot protect exterior components like a slab from frost. That is also not necessary. And so a card of the house of cards breaks due to supposed expert knowledge from the internet! What is needed is drainage. Namely, to drain water beneath the new slab. For this, one must know or assess, in addition to the topography surrounding the building, the composition of the soil. Clayey soil and a pit filled with gravel are completely pointless because water cannot be drained in this case. If you have “normal” soil, then a gravel layer is sufficient so that water cannot accumulate under the slab.

There is no SUCH THING AS “BETONESTRICH”! Concrete and screed are distinguished by their method of installation, their grading curve, and their flow behavior. These are all different for concrete and screed. Firewater, known from Wild West movies as a term for ALcohol, is known, but the term otherwise makes no sense due to its internal contradictions. The same applies to “Betonestrich.” A misleading term which unfortunately can be found publicly (in hardware stores).

Back to the topic. I cannot and do not want to give you any construction recommendations here. Anyone who thinks they can build a trade with their own hands MUST be aware of the applicable technical rules. Whether layperson or expert makes practically and legally no difference. Although I have already given you sufficient indications in my last posting about how thick the supporting structure (here: the screed in the outdoor area) should be and how the drainage beneath the slabs should look. With 2 cm slab thickness, these do not have self-supporting capabilities. They must therefore not be laid on pedestal supports but must be able to transfer point and surface loads to a correspondingly flexurally resistant substrate under pressure!!

I can only advise against trying to produce such a planned slab as a layperson on your own and only with the half-knowledge of the internet, without the corresponding expertise and only with the help of the local hardware store (as material supplier). The risk of total damage is simply visible in the background. At least to the expert...

Regards: KlaRa

Hello KlaRa,
Thank you very much. Everything sounds understandable so far.
What I haven't quite understood yet, however, is exactly how the drainage mat works in your description.
Shouldn't the drainage mat be above the screed (between the screed and the tiles)?
Water usually penetrates from above, e.g. through the joints.
The water doesn't drain through the screed, so it would have to be drained above the screed.
Best regards
Thorsten

What I have not quite understood yet is how exactly the drainage mat works in your description. Shouldn't the drainage mat be above the screed (between screed and tiles)? Water usually penetrates from above, for example through the joints. The water doesn't drain through the screed, so it would have to be drained above the screed. Regards Thorsten

You notice that the topic is complex. My answer to your question: There is the possibility to install a screed on a drainage mat and also to seal the screed surface and apply a drainage mat on it, on which ceramic tiles or slabs are then glued into the thin-set mortar. Both are possible. In the first case, the drainage mat serves to ensure that the screed, which is always porous and allows (rain) water to slowly pass through its structure, does not "stand in water with its feet." This would be the case if the screed in an exposed outdoor area was only built on a separating layer and no upper sealing and drainage layer was considered. Then the screed can "freeze apart" due to frost effects through ice formation and the associated destruction of the structure. ------------------------------------- Regards: KlaRa