Upgrading the sawmill triggers the Prestige mechanic.

Each new sawmill level gives you prestige rewards and a higher income multiplier, but your production line (machines and layout) starts from scratch.

What stays with you:
-Diamonds
-Reputation
-Biz points
-Chests
-Manager cards
-Your Workshop

 

Your progress isn’t lost - only the sawmill production setup restarts so you can build a more efficient one with your new bonuses.

 

Please note that you cannot return to the previous sawmill level. You keep diamonds, reputation, biz points, chests, managers cards, and your Workshop. Based on your previous experience and the new managers, you might develop your new sawmill differently. 

Please note that you can't come back!