Problems Insuring Properties in Portugal

We are purchasing an apartment in Praia Del Rey and have been advised that a building policy is infoce covering the main structure - external walls, staircases and patio's however we are resonsible to arrange insurance for the internal walls and ceillings.

This does not make sense to us and the  complications that would be caused if each individual unit was insured under a separate policies does not bear thinking of. For example if there was a fire which policy would repair our floor which in turn would be our neighbours ceiling?. Distinguishing between a common area and a individually owned area would also cause problems.