Recessed balcony, how to seal the concrete floor? Water glass, varnish?

[bjogul]

Our house from 1970 has a balcony recessed into the roof. When it snows and rains, this ends up on the balcony floor (concrete). In one of the corners, there is a floor drain for drainage under the roof tiles. All rain from the roof above the balcony is directed to the "wrong corner" and has to cross the entire surface to reach the floor drain. The slope to the drain is fairly OK, and usually, this works fine. But during very heavy rainfalls, water can penetrate the house. We have considered putting a roof over the balcony, but we don't see a reasonable solution for it. Besides, it would be expensive, and normally, the balcony works fine.
I have seen online that you can surface treat concrete to make it waterproof. But there are different materials/methods. Anyone got tips about this, and can you do this yourself

Edit: the problem is not that the downspout is in the wrong corner, and it cannot be moved. In the "right corner" is the balcony door.

There are a variety of preparations and methods for surface treating concrete (silane, water glass, soap, wax, oil, paraffin, resin, lacquer, etc.). Some might work a little better than others or can give different color and gloss to the surface. Besides binding the dust, you also want them to make the surface somewhat dirt-repellent and easy to clean.

 

[Rickard.]

None of what you mention is waterproof, there are other/different advantages to the various treatments but you need a waterproof layer that prevents water from penetrating the concrete.

 

[snuttjulle]

Isn't it possible to direct the water further to the right in your picture so that it ends up on the roof instead? Or a pipe that follows the roof down and out over the edge?

 

[bjogul]

None of what you mention is waterproof, there are other/different advantages with the various treatments, but you need a membrane that prevents water from penetrating the concrete.

Correct. That's what I'm after. Which membrane is used in this context? I thought Vattenglas did just this.

Can't the water be diverted further to the right in your picture so it ends up on the roof instead? Or a pipe that follows the roof down and out over the edge?

Well, the problem is also that the balcony itself is open/roofless. That is, the gutter only contributes to the main problem, namely that the construction involves an opening in the roof.