Split the mesh of treads and Risers of the stairs

Hi,

I have joind 3 breps (treads and risers of stairs ) and parapete to applicate mesh component, so I got one list of meshs, so to get the initial breps (with the mesh generated) I used SPLIT LIST, it works to get the mesh of the parapete but I can not get the mesh of treads and risers separated, I thought of Scalar product between The normal of the meshs and the Z vector but I got some results different to 0 and 1.

If you have any Idea please

Thanks

scala ciociola albaniagh.gh (54.8 KB)

Model 3Rhino.3dm (8.9 MB)

The raised/pedaled position doesn’t seem correct to me.