My little sister wants to make a spiral staircase for her cabin. I'm trying to help her design it. We came up with the idea of using a natural edge wood beam, and making the stairs so thick, and jointed to the beam with very large through mortise and tenon joints. The idea is that this alone is enough to support the stair and be strong enough.

So I told her, I could cut the wood for the stairs with my alaskan mill. But she is planning on making it this summer. So we would be working with fresh wet wood, probably for both the beam, and the stairs.

Anybody think this is a bad idea?

Cheers