Lumber is used to build a variety of things. One of the most important is upgrading authority buildings. Without lumber, the player won't be able to upgrade the tower to the keep. As players progress through the game, they will discover that they will need lumber to build buildings.
Lumber can be produced at a lumber yard. Putting wood into lumber yards will produce half the amount of lumber compared to the amount of wood. So, 2 pieces of wood will produce 1 lumber. The player must assign 1 or 2 villager(s) to work at a lumber yard to get lumber.
Lumber can be stored at both a small and large stockpiles, just like many other materials and resources.
Lumber looks like a beam of light brown colour.