What does a submerged torpedo flat cost a battleship?

Is the main penalty of a torpedo flat its volume or its weight?

Both matter: the installation adds weight and occupies considerable height and space inside the hull, creating a large and potentially dangerous compartment.

A torpedo flat consumes internal height and volume as well as contributing weight. It is described as a large void within the hull and a dangerous space for the ship. Removing the installation therefore raises questions about internal arrangement and protection as well as the tonnage available for other equipment.