The cumulative effect of several of "those little things" that are not done "just right" is what leads to job failure in thin-set installations. The singular "major" sins which can also cause failures are not often the culprits, since careful attention is usually paid to these. Perhaps the most common problem arises when the ceramic tile is installed over concrete. When the concrete is of a structural type ("elevated") and not on grade, the movement caused by the plasticity and shrinkage factors of concrete can destroy a tile installation in one year. Therefore, when using tile mortars on concrete slabs, observe the following precautions:

1. Direct to slab installation should be done only on slab-on-grade beds.

2. Structural slabs must be properly cured (28 days).

3. All slabs should be cured, stable, and free of cracks.

4. Never use a thin-set installation directly on pre-cast or elevated floors. Those installations require an isolation membrane.

5. Concrete curing compounds must be removed to secure a strong bond. When in doubt that a curing agent is present, test for one.

6. All dust, dirt, and foreign materials must be removed from the surface before to installation.

7. Hard steel troweled slabs must be scarified in order to obtain proper bonding.

8. The trowel used to install the mortar must meet the requirements set down by the mortar manufacturer for the size and shape of notches. Overly worn trowels no longer meet their original specifications.

9. Tiles must be beat in to obtain proper adhesion.

10. Large surface areas require expansion joints, as do locations where the tile abuts restraining surfaces and over joints in structural flooring.

11. Thin-set mortars should be mixed slowly, or by hand, in order to prevent air entrapment and consequent loss of strength. Never use high speed drills. Being alert to these few simple precautions will aid in installing a thin-set tile surface that bonds properly and stays that way.