The paper shows a defective flat roof over a multistorey garage on which parking places were designed. Due to the damage which occurred there, the owner was forced to repair, among others, the roof surface,which simultaneously functioned as a waterproofing layer. It was necessary to carry out subfloor testing in order to decide whether the new roof surface could be placed there. After a thorough analysis of the test results, a way of carrying out the repair works was recommended.

Keywords:multi-storey garages, flat roofs, waterproofing, surfaces.