Below is what I would do, based on my understanding of what it is you're after achieving, please let me know if I get something wrong eg Have misunderstood anything or have missed any of your questions (I believe I've covered all of them below).
From above comments: When that is covered, I want to pave the balcony with small garden rocks, I have already bought them, they are flat, glued to some farbic sieve in squares.
I'm going to assume a total thickness of 25mm (1inch) for the above material, and you know how to attach this material to the new concrete top slab. Please correct me if I'm wrong on those assumption.
I would say you want to end up with a minimum of a 50mm (2inches) step down from top of sill to finished balcony level.
Totally clear the balcony, work area (size: 710mm x 319mm)
Do I need to clean/set up those metal parts, cover with something, to stop rust and not let the flexibility of metal handrail shatter my new layer.
How to set up concrete "box" (to make concrete stay in place, and stop it falling off the balcony sides), there is hardly place to connect any temporary wooden box for that, ideas?
Seeing as the balcony isn't that big (size: 710mm x 319mm) you could use something like, "Bar Clamps" or "Pole Clamps" (2 would be enough), to pin (clamp) some shuttering material to the outside faces of the existing balcony concrete slab (against the 2 shorter sides). This would probably be easier and safer to do from the balcony below (if your below neighbour would allow you that access).
Make sure the side shuttering has a "slight" fall on the top face (over a distance of 319mm, 10mm would be enough), so that the new concrete will slope away from the door (sill), thus allowing any water to drain away from the building.
You could then attach shuttering material along the front face via connecting it to the side shuttering pieces.
Do I need any layers between building panel and my new layer?
- Paint the top face of the existing balcony concrete slab and up the face of the sill with 2 coats of bitumen paint. This will provide some protection to the existing concrete from moisture penetrating down from above.
Which concrete should I use?
How thick should that layer be, how many sacks of that stuff will I need (will give balcony area m2 later)
How thick a metal armature will be enough for this job?
Wire diameter of bought armature (in picture 8): ~0,9mm
That will be fine, just place a single layer in the middle of the new concrete top slab you pour.
After you finish installing your "garden rock fabric" and have allowed everything to dry properly, I would:
Good luck, and please let me know if you have any questions related to what I've written above.
You need to understand the properties of the materials you're planning to use.
Rammed earth is earth, chalk, lime and gravel, mixed into the right consistency and proportions for strength and longevity. It's then rammed into a form work to form a solid mass.
As it is earth, it can wash away like earth so it's susceptible to water damage if not properly protected from water. As a garden retaining wall I wouldn't therefore recommend it because it's going to get wet frequently. They can use it on houses because the roof and it's overhang protects the walls from constant moisture.
If it's a particularly high wall you would normally put seep holes into the wall to allow for drainage. Naturally, even with plastic pipe in the hole I would think it'll not last 100 years. So if you're thinking of using rammed earth, I'd definably line the wall with plastic.
Also, earth does crack as it expands and contracts. You fix the cracks with more rammed earth mix. People with these types of houses generally have to patch cracks every few years for this reason. But, it's a very organic material to work with and they would be aware of this... it's a choice you make when you build with it.
You could use cement in place of lime. That may make it last a lot longer and increase it's strength. I've seen this work for some structures and it may require some experimentation being out in the open.
Concrete on the other hand does last a long time if properly prepared.
It also can crack as it naturally expands and contracts. To prevent serious cracking you need to cut it every few meters and fill the gaps with a flexible compound. You might notice that as you drive over some concrete highways you'll hear a bump, bump, bump, noise. That's the wheels going over the horizontal cuts in the concrete designed to allow for expansion and contraction and prevent cracking. If it's a big retaining wall you'll need these cuts.
Concrete is also porous so water can be absorbed. You can imagine that concrete that has absorbed water that freezes won't be good for the concrete right? Because it could cause it to crack, and it does. So you need to get a grade of concrete that is less porous and stronger (and make sure it's thick!). Talk to your concrete supplier if you got this route and make sure you get a stronger grade and that when the concrete is poured it is not too wet.
If I were you I'd consider using a different material all together.
Have you considered brick? You can get some flexible mortars so you won't get the same cracking issues as you would with concrete and it will look more attractive in my opinion.
Another option is to use a hardwood. Down here in NZ we call them railway sleepers. You can stack them, bolt them together and form a pretty nice retaining wall. It's strong and attractive. I'd paint the side where the dirt is touching it to protect the wood, or use a plastic barrier or paint on barrier like mulseal. It probably won't last 100 years but it should last at least 50 if well prepared and looked after.
By the way, some woods like Jarrah can last a very long time without any treatment. We can sometimes get Jarrah poles used by the electric company for the overhead wires. They pull them out of the ground and they are still as good as when they went in over 50 years ago. So, some hardwoods can really last.
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Honestly, I don't think you can. The problem is railings such as this rust from the inside out. The outside gets primed and painted while the inside never gets any kind of treatment.
Aside from using solid "tubing", which is unrealistic, the only other thing I can think of is to "try" to treat the inside of the tubing in areas where water can seep up in to the tubing, such as an anchor point.