Balcony renovation, questions about the substrate for tiles

Good day, I am new to this forum and hope to get some support on a topic that interests me a lot but unfortunately I don’t have much knowledge about yet. I plan to redo my balcony this month. Current state of the balcony: 12 square meters 20x20 floor tiles 3cm, all fixed, no major damage. Walls are covered with bricks up to about 30 cm. Plan for the renovations: 120x40 wood-look tiles (Nordic) Remove bricks from the walls, plaster, sand and paint white. Now I have a few questions: Should I chisel out the old tiles, level the floor afterwards, prime it and then lay new tiles or should I do tile on tile with appropriate priming beforehand? Any tips or should I proceed completely differently? How useful is a decoupling mat in outdoor areas? Which primer, tile adhesive, plaster etc. do I need or can you recommend? I am very grateful for all tips and suggestions.

Hello questioner. Especially for floor constructions on balconies and terraces, several things must be considered; particularly when the surface is exposed to the weather and (an additional increase in difficulty) there is living space underneath the terrace or balcony. However, we do not know any of this based on your information. Considering the execution of the transition (probably between living space/terrace), I assume that the balcony is largely covered. The so-called "floor tiles" of the outdoor area are (at least judging by the appearance) probably rather concrete stone slabs. Now let us assume the ideal case that waterproofing was planned and applied during the installation of these floor slabs. During a dismantling, all of this would be destroyed – and according to the current professional standards, it must be rebuilt completely with a waterproofing layer + slope! This also includes taking a very close look at the current situation regarding the drainage of surface water (rainwater), especially regarding its functionality. Assuming a proper adhesion bond of all floor slabs at this point, the entire surface would have to be ground with a diamond blade, thoroughly cleaned of dust by vacuuming, and primed with a primer for non-absorbent substrates. Since it is located outdoors, all dispersions can be forgotten as primers! We are therefore talking about reaction resin primers, which must also be broadcast with fire-dried sand while still wet (i.e., before curing). On this, tiles at least 10mm thick can be glued with a suitable tile adhesive in a medium bed, and jointing can be carried out. A decoupling mat is of little use with this construction. What should it achieve? Decoupling mats are intended solely and exclusively for problematic substrates. For example, cement screeds with unstable zones. But in any case, a water-carrying primer or waterproofing layer beneath the existing floor slabs was required here, because it can never be excluded that rainwater penetrates the floor construction through the joints. What do these lines tell us? They tell us that for complex trades, the appropriate expertise for execution as well as knowledge of the current professional standards are necessary. If you lay directly on the existing slabs, you can "turn a blind eye." At least fate will deal with it that way.... However, if the slabs are dismantled, things get complicated – at least if you don’t want to face a total loss in 1 to 2 years (and call it your own). ------------------------------------- Not every trade is suitable for the DIY enthusiast! Good luck: KlaRa

Hello questioner. There are several things to consider especially for floor constructions on balconies and terraces; particularly when the surface is exposed to the weather and (an additional increase in difficulty) when there is a living space beneath the terrace or balcony. But we do not know all this based on your information. Considering the execution of the transition (probably between living space/terrace) I assume that the balcony is largely covered. The so-called "floor tiles" of the outdoor area are (at least judging by the appearance) probably rather concrete stone slabs. Let us now assume the ideal case that waterproofing was already planned and installed when laying these floor slabs. In the case of a deconstruction, all of this would be destroyed – and according to the current rules of the trade, it must be rebuilt completely with a waterproofing layer + slope! This also includes taking a very close look at the current situation regarding the drainage of surface water (rainwater), especially with regard to functional suitability. Assuming a proper adhesive bond of all floor slabs at this point, the entire surface would have to be ground with a diamond blade, thoroughly cleaned of dust by vacuuming, and primed for non-absorbent substrates. Since it is located outdoors, all dispersions can be forgotten as primers!! So we are talking about reactive resin primers, which in the wet phase (meaning: before curing) must be broadcast (or have applied) with kiln-dried sand. Then at least 10mm thick tiles can be glued with medium-bed suitable tile adhesive and grouted. A decoupling mat makes little sense in this structure. What would it achieve? Decoupling mats are exclusively intended for problematic substrates, for example, cement screeds with unstable zones. But here anyway, a water-conducting priming or waterproofing layer beneath the existing floor slabs would have been necessary because it can never be ruled out that rainwater penetrates the floor construction through the joints. What do these lines tell us? They say that for complex trades the corresponding expertise for execution, but also knowledge of the current rules of the trade, are necessary. If tiles are laid directly on the existing slabs, one can "turn a blind eye." At least fate will treat it that way... However, if the slabs are taken off, then it gets complicated – at least if you do not want to face a total loss in 1 to 2 years (and call it your own). ------------------------------------- Not every trade is suitable for DIY! Good luck: KlaRa

Good day, I already thought so, yes I know that what one hasn’t learned shouldn’t really be done oneself. Since I myself am working in a trade, albeit another trade, I thought to get some information and get started, but wrongly assumed. So, that means the only option if I still want to do it myself, due to corona, saving money, etc., is: leave the tiles on and tile over them. Sand down the old tiles and prime? Then tile over again with weather-resistant tile adhesive? What do I have to consider at the edges of the new tiles where there is no wall? Oh, and as information, yes the balcony is covered as far as the tiles go. Thanks in advance and best regards

I am always pleased when my cautionary notes find fertile ground. If we do not need to worry about an additional gutter to be installed on the open railing edges, the solution is quite simple. Suitable as a finishing element would be, for example, "Schlüter-BARA-RKK/-RKKE" (or comparable profile bodies). The former is a T-shaped finishing profile with a short drip edge for the free edge area of covering constructions on balconies and terraces. The support leg is glued onto the old covering before laying the new tiles, and then the new tiles are laid or worked on. -------------------- Good luck: KlaRa

I am always pleased when my warning hints find fertile ground.
If we don't have to worry about an additional gutter to be installed on the open railing edges, the solution is quite simple.
Suitable for finishing would be, for example, "Schlüter-BARA-RKK/-RKKE" (or comparable profile elements).
The former is a T-shaped finishing profile with a short drip edge for the free edge area of covering constructions on balconies and terraces.
The support flange is glued onto the old covering before laying the new tiles, and then the new tiles are laid or worked in.
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Good luck: KlaRa

The T-shaped finishing profile sounds very good, I had something along those lines in mind. Does it then need to be additionally sealed with silicone or something similar?
How is the transition from the new tile to the aluminum profiles of the door and the transition from the new tile to the wall ideally done? Simply with the chosen joint filler?
Is the procedure I described in the previous comment correct? I would rather not forget anything. It seems easier and simpler if the old tiles and the old waterproofing remain, but I still don't want to forget anything. As a small info, the old door profiles shown in the pictures will be removed because new doors and windows will be installed.
Is there anything else to consider regarding tile spacers? I bought 3mm and a 10mm notched trowel, as I understood when gathering information, since the tiles are 120cm. Is everything correct so far, or any tips or mistakes on my part? Thanks for the very informative answers so far.
Regarding tile adhesive and non-absorbent primer, are there any products that are good to use?

Tiles can be installed "tightly" against finishing profiles, but they should not be.
Therefore, it makes sense to leave a 3mm to 5mm wide joint between the tile edge and the profile edge and fill the joint chamber in the upper third with an elastic sealant.
Currently, there is a multi-bent profile at the door. A similar one will be used there again. Probably a new fabrication will be necessary anyway due to the new door. The tiles will also not be laid "tightly" against the door here, which is why a joint (covered by the cover plate) will form within the new flooring before the door transition.
My recommendation here is to loosely place an expansion tape parallel to the door entrance before attaching the new cover plate and then only lightly press it with the cover plate.
A suitable expansion tape is, for example, "Hydrotite SS0330" from TPPH (or comparable).
Only 3mm wide joints for large-format tiles seem risky to me! I would go for 5mm because the tiles expand considerably on a balcony during warm seasons.
For a tile size of 1.20m length, the substrate must be very even (DIN 18202 Table 3 Row 4 = increased evenness). Check!!
Regarding priming: I already wrote: synthetic resin (epoxy resin, 2K).
Common tile adhesives are mostly cement-based and are therefore also suitable for outdoor use.
Prefer medium-bed adhesives, because due to the remaining ribs (and thus the resulting hollow spaces) below the tiles, that is: inside the adhesive bed, no frost damage can occur in winter.
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Signing off: KlaRa