Store room

Store room

"Store room is where Silver is reserved. Higher level store room can hold more silver"

The only purpose of this building is to increase the amount of silver you can hold maximum.

It however can hold more then maximum (especially early on in the game you will exceed maximum amount easily) but that will make you unable to sell or downgrade items and receive quest rewards.

Most buildings cost small amounts of silver to upgrade. Upgrading senatus however gives you (large quantities) of silver.