Not sure I am doing this correctly. Like a previous 'thread' on concrete flooring, I too, am having a nightmare. Took the carpet up in the hallway - having some stone/ceramic tiles laid. Underneath the carpet are 'Marley' tiles which were laid on the concrete floor when the bunbalow was built. Noticed a slight 'bulge' and some of the tiles cracked. Lifted those tiles and discovered a crack in the concrete floor right across the hallway. The crack is about 2mm wide and about 2mm high one side. No cracks visible on the walls either side of the hallway. What should I do about this? Tiler is coming on Friday. Please reply ASAP. Many thanks.