Updates to NavigationMesh after Actor is added

I am using UE 4.10. I am procedurally creating my terrain by spawning StaticMesh Actors side by side in my GameMode class. This means that my NavigationMeshBoundsVolume is not covering anything before then. How can I dynamically update the NavMesh so that my terrain can be walked on by AI? I am not having luck finding a solution for this in 4.10. Maybe 4.11?