Avoiding Common Errors When Using Tile Mortars
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
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.