Blender to Unity FBX Problems

Hello, I am relatively new to Blender/Unity and I am export a level design into a game i am making. I don’t want to use .obj becuase i dont want to texture mesh. So, I am using FBX. Whenever i export my FBX file or even my .blend file all of the wall and floors are transparent untill you walk past them. Is there any wat i can stop this? Thank you.

Have you make sure that the normals of the mesh is correct?

Re-calculate mesh in Blender ( Edit-Mode → Ctrl+N )

Calculate normals in Unity in the FBX import setting window.

It is the normals of your mesh in Blender. To fix this, you can goto Blender and goto “Cycles Render”. Then press Alt + Z. This will enable the textured view and you can goto edit mode and all the normals that are facing away from the camera will be painted dark blue / black.

Simply Click on them and press Ctrl + N or Ctrl + Shift + N.

Remember, if the normals are facing away from the camera, not only will you be able to walk through the mesh but also not be able to see it.

Hope this helps! I also had the same problem but I fixed it!