You can now put Buildings to your Storage space, where you can store up to 15 different buildings there.

To put a building in Storage, start by tapping on any building on the map
Then tap on the top left icon to show the EDIT menu:

Then tap on the blue button with a box inside:

The Building will then be placed into your Storage.

To access your Storage, tap on the Market button at bottom right corner of the screen:

Then select the blue tab on the right with a box inside:

You'll find your Buildings there!

Just tap on Place Item on the desired building to put it back on your map