First, I must mention that I am often questioned about the term "thinset." This is frequently used to describe a mortar tile installation. For example, one may say, "I used thinset." Actually, the correct definition of thinset as applied by the Tile Council of America (TCA) is that the term is used to describe the method of installing tile with a bonding material usually 3/32- to 1/8-inch in thickness. By this definition, a thinset installation would include organic mastic and epoxy systems.
There are three thinset mortars available today. One is dry set mortar and another is called latex Portland cement mortar. The third is a developed mortar system for bonding to exterior glued plywood.
What follows are bullet lists, organized according to the materials being used, of DOs and DON'Ts that should be observed for the type of installation being perfomed.
Organic Mastics
Just Do It:
• "Beat in" your tile.
• Use a type I mastic on cementitious backer boards.
• Apply enough mastic to surround the edges of mosaic tile.
Just Don't Do It:
• Don't grout for 24 hours (discoloration may occur).
• Don't use for exterior installations.
• Don't use on commercial floors.
• Don't "level" with organic mastic.
• Don't use over wallpaper.
• Don't use to install natural marble (staining will result).
• Don't set fixtures with mastic.
Thinset Mortars
Just Do It:
• Use the correct trowel size.
• Strictly follow the manufacturer's directions.
• Mix at the correct speed.
• Slake your mix.
• Beat in your tile.
• Check for proper transfer.
• Trowel correctly for oversized tile.
• Use the correct mortar for the tile being installed.
• Properly prepare the substrate.
• Use latex thinsets for porcelain tile.
Just Don't Do It:
• Do not over water.
• Do not speed mix.
• Do not add water after the original mixing.
• Do not use hot water from garden hoses.
• Don't spread too far ahead (to prevent skinning over).
• Don't install over concrete curing compound. Remove the compound instead.
• Don't install over asphalt adhesive.
• Don't install over unapproved membranes.
• Don't install marble over on-grade slabs subject to excessive moisture vapor emissions. (Staining could result.)
• Don't install ceramic tile or marble directly over expansion joints.
Grout types
Grouts are often cited as the ceramic tile industry's biggest problem. A variety of grout products are available today, so choose wisely. Consider the following grout definitions, as defined in the TCA Handbook for Ceramic Tile Installation, when deciding which product to use.
Sand-Portland cement grout - An on-the-job site mixture of fine sand and Portland cement with lime sometimes added. Damp curing is necessary.
Standard cement grout - A factory prepared mixture of cement, sand and other ingredients for joints 1/8-inch wide or more. It is also manufactured without sand for joints narrower than 1/8-inch wide.
Polymer-modified tile grout - Manufactured sanded and unsanded dry polymer may be in the factory mix. Dry polymer is re-dispersible with the addition of water at the job site. Otherwise, liquid latex may be added at the job site if the mortar does not contain the latex additive.
Epoxy grout - A two- or three-part system that may be manufactured in various formulations. Consult the manufacturer for specifics. Epoxy grout is used extensively in industrial and commercial installations where excellent bond strength and resistance to impact, chemicals and high temperatures is required.
Furan resin grout - This is a grout system that utilizes furan resin and hardener. It is also used in industrial and commercial installations for the same reasons outlined in the entry for epoxy grouts.
Common grout problems
Some of the more common problems associated with grout installations, and the potential reasons for their occurrence, are outlined below.
Grout Cracking
• Wall tile grout not packed firmly.
• Too much water used in mix (grout shrinks).
• Excessive substrate deflection,
• Re-mixing grout with more water after hydration has already started.
• Movement of substrate.
• Setting mortar too high in joints.
• Some organic mastics will discolor.
• Extremely high absorption of tile (be sure to dampen tile before grouting).
Grout Discoloration
• Too much water in grout mix.
• Unclean mixing water used.
• Wiping grouted joints too soon and with too much water.
• Too much mortar in joint. (Grout should be filled to two-thirds of the joint's depth.)
• Poor or no curing.
• Old grout used.
• Grouting a large area on different days.
Mottled grout
• Inconsistent color (mottled).
• Overglaze on tile edges causes uneven curing.
• Grout was mixed too wet.
• Grout dried and cured too quickly.
• Excessive cleanup water used (which draws out color pigments).
To improve your chances for a problem-free grout installation, I recommend you observe the flowing DOs and DON'Ts.
>Just Do It:
• Mix properly to thoroughly blend all ingredients.
• Use a clean, sharp-edged grout float.
• With "older" grouts, be sure to give the product a good shake and blend ingredient in a dry mode.
• Use the correct amount of water or latex as per the manufacturer's instructions. (Do not fly blindly!)
• Scrape grout joints that are filled with excessive mortar.
• Dampen tile edges if job site conditions are excessively dry and hot, and the tile is porous.
• Allow grout joints to start firming up before cleaning.
Just Don't Do It:
• Don't over mix.
• Don't add water or latex.
• Don't grout too soon.
• Don't start cleanup too soon.
• Don't use excess water in cleanup.
I hope you'll carefully reflect on this checklist of bullet points. Hopefully, it will help you avoid problems and produce a high-quality installation that lasts indefinitely. I've tried to be very straightforward in my instructions of what to do and what not to do. Hopefully, if you've read between the lines a bit, you realize that the most important message contained in this article is not simply to Just Do It - but to Do It Right.
