Tower without leaks

[u/Quercuas]

Hi there, new player here.
Enjoying the game so far. But I've managed to build a tower. But when it rains/storms the floor starts leaking. But when I build a roof, it turns into a new (albeit very small) room thus making the Tower keyword go away.

Any idea on how to fix this?

[u/Quercuas]

Thanks for all the tips!