Do you have a garage attic and want to communicate with the outdoor terrace you have on top? Surely because of having to go through the common area of the building do not take advantage of everything you would like the terrace that you have on top of your apartment and of which you have exclusive use and enjoyment. You can solve it by opening a hole in the slab (roof), putting a garage attic stairs and directly communicating both spaces!
First of all you have to know that a slab (roof) is a structural element and that whenever you touch a structural element you have to ask for a building permit in your town hall. In the second place you should know that in this type of works, you have to ask permission from the community of neighbors and give your approval. Do not be fooled by the builders or masons who tell you that “they can open the gap for sure.” It is sure that they will be able to open the gap, that is clear, but not with sufficient security guarantees.
To open a stairwell in an existing floor, you must first know what the structure of the building is like. Once studied, the necessary reinforcements must be calculated so that opening the hole does not represent a risk for anyone. It does not have to be complicated, but it is essential to do the previous study and the subsequent calculation.