I believe there is a level of damp that is acceptable for garages/storerooms/basements which are not considered habitable. But cascading water is not “damp”. And even if you were in a townhouse/villa with your own garage attached, should water come up from under the concrete slab, that is the OC responsibility. So would definitely be so in a unit block where both above and below the slab is CP.
Concur with Whale in sending letter to OC stating that you hold them responsible. Send copy to SM. Leave a paper trail.