Stacking

Overview
All tiles with this symbol in the upper left corner can stack. Stacking means that you can place multiple of the same building on a single tile, up to 5 placements. Tiles that can stack include Tenements, Office Towers and Silos. The appearance of the building changes with how many buildings are stacked.

Strategy
It is almost always in your best interest to stack buildings. The effects stack, and you don't waste space on the board that could be filled with valuable point collecting tiles. However, don't feel bad if you can't hit the max stack of five every time you do stack something. Sometimes you need 3 or more of the same card to hit that max stack. Overall, stacking is a valuable resource to exploit.