All ceramic tile installations have gaps between the tiles, called grout joints. These must be sealed to prevent moisture from seeping in and getting behind the tile, where it can weaken the adhesive or create mold, mildew or rot problems. The traditional material to fill those gaps is grout, but there are alternatives in the material used and the application.

Tiles need grouted seams.

Choose a Gap

Before laying the first tile, choose a gap size. Bathroom wall and kitchen back-splash tiles generally are butted tightly together, with only small grout joints. Floor tiles usually have larger joints. A general rule is to fit the grout joint to the tile -- small joints for small tiles, bigger ones for bigger tiles. The style of tile also will affect the choice; some clay tiles (terra cotta or Mexican tiles) have very wide gaps, up to 1/2 inch.

Grout Starts with Cement

Grout is basically cement, but with various additives to affect the installation and durability. The main types are sanded or non-sanded; sanded grout has very fine sand mixed with the cement and is used on joints at least 1/8-inch wide. Non-sanded is pure Portland cement and is used on smaller joints. All grout comes as dry powder that must be mixed with water. A dry-set grout is used on tiles that are dry when the grout is applied.

Sanded and Non-Sanded

Major cement grout alternatives are sanded, which is mixed on site with cement, fine sand and water; non-sanded dry-set, which is cement, fine fillers, a water-retention additive and coloring, to be used on dry tiles; ready-mixed sanded grout, with cement, fine sand and coloring, to use on moistened tiles; latex-modified grout, with a latex polymer added to the cement and sand to increase bonding ability and water resistance.

Non-Cement Grouts

Some grouts do not use Portland cement as a binder but substitute latex epoxy. Some are available in sanded or non-sanded versions, but most replace sand with other fillers designed to resist specific chemicals or other conditions. A 100 percent epoxy resin grout uses silica fillers, an epoxy hardener and coloring; it resists staining, water and chemicals. Modified epoxy grout uses some cement, is harder and more resistant to stains than traditional grout.

Other Grout Types

Two other types of grout are Furan and caulking. Furan substitutes furfuryl alcohol for water and makes a grout that is highly resistant to chemicals and acids. Tiles must be coated with wax before Furan grouting, and the tiles must be steam cleaned after grouting. Caulk comes in tubes and is squeezed into joints from a tube or caulking gun. It normally is used to seal 90-degree corners, places where tile meets a wall or around sinks and other installations. Some types dry hard, while others remain flexible and rubbery.