hi, wonder if anyone could help, weve just put some parquet flooring down but laid it in strips, its block and beam flooring, with 50mm of screed, it has wet underfloor heating underneath, we used the dipping bitumen to bond he parquet straight onto the concrete floor, all is well til the floor warms up then then the strips open up, the floor is 4m x 6m and appears to open up about 5mm accros the 4m width, i presume this is the slab thats expanding, its more noticable this week as weve been plastering and the cracks are visible in the dust (see pic), just wondered if anyone had an ideas how to stop it, dont want to take the floor up again as it took alot of putting down, im not so bothered about the cracks im more concerned that the blocks will lift in a short time withe the continual expanding and contracting.