The grid cell size determines how thick your walls will be. This cannot be changed once you start drawing — it will match the scale of your floor plan.
Fine
8 px · thin walls
Standard
12 px · recommended
Bold
16 px · thick walls
Floor GridWallsRoomsEraseFill
Tool: Exterior Wall—Cells painted: 0Shift = straight line · F = bucket fill · E = erase · Ctrl+Z/Y undo/redo