Sorry but not sure what you mean. I always add vertical/horizontal beams around each window opening just to make it more presentable (and its a good way to frame a building before filling it in). But as mentioned, I tried filling in every window space upstairs til it was completely dark and covered, and it still won't shelter everywhere. I also used iron poles around the building to add support, so are those counted as vertical poles?

I really think the height factor is playing a role in this, but I'm sorry I just don't get what you mean, if you could present an example with in-game building that may help.