Lighting Problem when using Baked Lighting + Custom Made Meshes

Ok, so I made a custom mesh using the Modelling tab. For some reason the shading is very wrong when I build the lighting, and I don’t know how to fix it.

Images are below :

Can someone tell me whats wrong and how to fix it?

Hi @LeadingSumo9835,

Could you please attach the before/after so I can see the difference you’re referring to?