There are some buildings that you can only build once (for example, Statue of Kane and the Redeemer/Reclamator/Hexapod Facility). However you can actually build more then one. Get additional Construction Yards (build MCVs at your War Factory), then place the Construction Yards. You now have more than one building queue. Start making the building you want more than one of at all your Construction Yards. When they are done, place them. The more Construction Yards you have, the more statues or facilities you can make.