Each resource has a storage class which defines in which building it can be stored. The storage class is shown on the resource icon:
You can only send resources to a building which either needs the resources for production, or is a warehouse which allows the resources to be stored.
- If you try to buy a warehouse you are be able to see which resources it can store:
- If you request resources from a building you are also able to see all the resources that it can store: