The most popular stone are made from travertine or limestone. The installation procedure is to set the stone tiles in a cement mortar bed on a concrete slab.

The natural make up of the stone tiles, the setting materials, and the concrete slab they all have something in common, calcium, Because of this naturally occurring organic mineral there is a problem that can present itself.

Have you ever seen exterior stone flooring that has white film or even a white build up on the surface or around the grout joints?

If you have, this is efflorescence! It can be a bugger to get rid of.

Efflorescence is a naturally occurring by product of the concrete curing process.

As the fresh poured concrete starts to harden, calcium hydroxide is released and migrates to the surface of the slab and in turn migrates up to the bottom of the stone and up to the stone surface. The wetter the concrete was mixed the more the calcium hydroxide is released, hence the more migration of calcium build up. Concrete takes days to completely cure and the calcium can continues to leach out for quite some time. If you are having a new slab poured and have a say in the matter, try to have your contractor mix the concrete as dry as possible. (They hate to do this because it is harder to place and work the concrete)

Another thing that can help to minimize efflorescence is to have them slow cure the concrete slab, by keeping it wet after it sets.

This is easy enough to do, just wet the slab with a hose and keep it covered with plastic for a couple of weeks and let it slow cure.

If you are having stone set on an existing slab have your installers use a latex additive mixed into the setting cement this encapsulates the setting cement in a kind of plastic. It is kind of like pouring elders glue in a cup of sand and letting it dry. The only difference is the "admix" does not emulsify like the glue would. Adding this can help keep the migration of calcium to a minimum.

After your stonework is complete keep it sealed with a good penetrating sealer on a regular maintenance schedule.