Hi,
I have a used spiral staircase in galvanized steel that I plan to mount to a loft on the outside of a building. The building is about 100 years old and constructed with double brick walls (canalmur). The facing brick is tied to the inner wall, and as I understand it, the outer wall/facade is not suitable for anchoring heavy objects. It probably can't handle large tensile/compression load horizontally (correct me if I'm wrong). I believe, therefore, that one should avoid anchoring the staircase's top landing, as there's a risk to the facade if the staircase were to move a bit.
The spiral staircase is not a monster, 13 steps and about 230 cm in height to the top landing. However, the staircase is heavy since it's made of steel, possibly weighing several hundred kilos. I understand that spiral staircases are "self-supporting" and all the weight is transferred down to the ground where the spindle (the pipe) stands. The staircase is used, and the base attachment, or base, is missing - it ends with just a pipe against the ground.
My thought is this: It must be anchored to the ground and have a stable base. I'll cast a substantial foundation (as is normally done) and cast a pipe that I can fit the staircase's spindle pipe/center pipe onto. This will fix and anchor it. Then, I'll avoid anchoring the top landing to the facade so the staircase can "settle" without pulling the facade apart. Can the staircase stand like this and maintain its balance on its own, even when walking on it? Again, I'm thinking of a quite substantial pillar. The top landing is sturdy, so it in itself won't need anchoring to withstand being walked on; rather, my question is about the entire staircase not being able to tip/become dangerous.
If I do this, the staircase's circular spindle pipe will load the concrete right where the embedded thinner pipe meets the concrete. Do you think it will hold? Imagine a hollow pipe cast in concrete and you slide a pipe over it and load it, so the load occurs right at the concrete's edge against the embedded pipe. Admittedly, everything happens in the center of the foundation, but I think you understand...
Thoughts?