Spline Builder uses 3 different snapping values listed here

Snap Value 100

  • BP_BuildingTool
  • BP_CeilingTool
  • BP_MidTool
  • BP_RoomTool
  • BP_FloorTool
  • BP_WallTool

If you change the meshes size in the Tools settings to 200 or 400 then you will also need to change the snapping value to 200 or 400.

Smaller snapping values should be used when making small adjustments such as adding pillers on to the ends on walls and adding features like door and stairs we recommend using 50 or 5 depending on how precise the adjustment is, keeping the tools and meshes on the grid means that the meshes and tools can snap together with out any gaps or issues with line them up correctly.