Vertical collider mesh help

I made a level design in Maya and imported it into unity to be used as a first person map. However, I have the ground collider working to where I can walk on it fine, but when I bump into walls, I go right through. It's not all the walls, only some. The map is all one object so all options are applied to the whole. Could this have something to do with the walls being planes instead of solid boxes? Or is there some simple fix I don't know about? This is for a college project so I would appreciate quick responses if possible.

I would advise you to create box colliders for each wall manually and increase their scale on the Z axis a little. Thin layers of collision geometry is hard to detect for the engine.