An installation for storing of natural gas or some other fluid comprises a lined underground storage space. Inside the rock wall of the storage space there is a concrete layer for supporting an inner impermeable lining layer. According to the invention, the concrete layer has a crack distribution control reinforcement layer closer to the impermeable lining layer than to the rock wall in order to divide large cracks into smaller cracks and distribute the cracks over a larger area of the impermeable lining layer. Further, also according to the invention, there is between the impermeable lining layer and the concrete layer a non-binding sliding layer to facilitate relative movements between the impermeable lining layer and the concrete layer.