Movement is certainly the most serious problem in solid floors, as explained in sections 2.3, 3.5 and 4.2. Although movement joints must be provided to accommodate shrinkage and expansion arising from fluctuations in temperature and moisture content, it is the changes during and following construction that actually cause the most serious problems. In a building with a reinforced concrete frame, the reinforced concrete upper floor slabs are integral with the frame and the whole structure suffers uniform movement due to fluctuations in temperature and moisture content, particularly shrinkage following construction. If rigid ceramic tiles are laid on the floors, it is essential to limit the size of the tile bays and to provide movement joints between the bays, as well as between the tiles and the walls. If these movement joints are omitted the shrinkage of the concrete floor slab will tend to dislodge the rigid tile flooring, but in addition the shrinkage of the structure will compress the tile flooring and doming may develop. Sometimes the tiling becomes detached from the floor through a shock wave related to some incident, such as something dropped on the floor, flexing of the building through wind or earthquakes, or even an explosion in the vicinity, the tiles then being thrown upwards suddenly, perhaps injuring persons within the room; sudden detachment of tiles can also occur from walls, as described in section 11.3, and the same problems can occur with rigid stone flooring such as marble or granite slabs.