Posted by Larry on October 19, 19100 at 20:49:47:
In Reply to: Re: Refinishing basement - What type of floor to use? posted by Evan Lauridsen on October 19, 19100 at 07:40:02:
Efflorescence is the migration of soluble salts from the grout or backing material to the surface. When it comes in contact with the air, it reacts with carbon dioxide forming a white salt.
While ceramic tile is highly water resistent and even waterproof in some types (depends on the tile) it should not be considered a water barrier. In other words, if water is migrating up through the slab a waterproofing membrane should be installed before the tile is installed otherwise the water may continue to migrate up through the tile itself. This can not only cause efflorescence but also tile/mortar failure.
While a waterproofing membrane will help to reduce the migration of water from slab to tile mortar bed it will not eliminate the possibility of efflorescence occuring. Most of the soluble salts come from the mortar and grout used to install and finish the tile. By the way these salts can migrate through and show up on the tile itself.
For what it's worth, the source of efflorescence is calcium hydroxide, a by product of the hydration of portland cement. By installing the waterproofing membrane and properly mixing the thinset and grout, you can greatly reduce the chances of efflorescence occuring. A deep penetrating grout sealer would also be recommended to seal the grout joints after proper curing times has elasped. Should efflorescence occur there are a wide variety of tile products formulated to remove these deposits.
I would recommend dark colored latex modified grout, perhaps grey considering the foot traffic. White grout can be difficult to maintain and any surface staining will show up like a sore thumb.