To prevent cracking when tile is applied directly to concrete, what should be provided?

Providing control joints when tile is applied directly to concrete is crucial for preventing cracking. Control joints are intentionally placed fractures in the concrete that allow for the natural movement of the slab as it expands and contracts due to temperature changes and moisture. By accommodating this movement, control joints help to prevent stresses from building up in the tile, reducing the likelihood of cracking or other forms of damage.

In the context of tiled surfaces, the control joints guide where any cracks will occur, keeping them away from the tiled areas and maintaining the integrity of the surface. This is particularly important in environments where temperature fluctuations are frequent or where the concrete slab is subject to settling.

While other options like expansion joints, slip sheets, and reinforced mats serve specific purposes in construction, they do not directly address the need for controlling cracks in the context of tile application on concrete. Expansion joints help with larger shifts in concrete structures, slip sheets are more about reducing friction between surfaces, and reinforced mats deal with strengthening applications rather than movement control.