Grout of various types and formulations is used to fill the space between tiles providing a hard, dense, and long-lasting joint filler. Grout also yields a hygienic capacity of filling the grout joint while also allowing designers and consumers to select from a myriad of colors to compliment the overall design of a tile project.

While grout performs well in the above description, it normally sets hard and ridged, hence not allowing for movement to be accommodated. It is for this reason that the use of a caulking or sealant is desired to meet the demands of movement and moisture. 

A sealant or caulking in a tile assembly functions as a method of closing a gap between the tile and an adjacent surface. Its purpose may be to provide a water-tight seal in a wet or exterior application and/or to provide for movement. However, all sealants are not created equal.  

Several years ago, the committees of the American National Standards Institute (ANSI) and the Tile Council of North America (TCNA) Handbook changed the verbiage in these documents to differentiate between caulking and sealant. While both fill the space between tiles and adjacent surfaces, sealants perform better when handling movement and wet area requirements.

The National Tile Contractors Association (NTCA) Reference Manual glossary provides the following definitions:

Caulking compound: a soft, plastic material consisting of pigment and vehicle, used for sealing joints in buildings and other structures where normal structural movement may occur.

Sealant: an elastomeric material that is used to fill and seal the expansion joint. This material prevents the passage of moisture and allows horizontal and lateral movement at the expansion joint.

The key word above is “elastomeric” which means rubber-like (flexible) and being able to resume its original shape after being stretched or deformed. ANSI A108.01-3.7.4.1.1 states, “Unless otherwise specified, use sealants complying with ASTM C920, which designates sealants according to type, grade, class, and uses. The following are suitable for use in tilework.  Suitable sealants include silicone, urethane, and polysulfide.”  Likewise, the TCNA Handbook calls for the use of one of these three sealants.

The 100% silicone remains intact and shows no visible signs of losing its bond to the tile while the siliconized acrylic caulking broke loose from the tile edge after bending the joint.

Photo: Scott Carothers.

There are many types of caulking/sealants on the market which can lead to confusion as to which one to select. A 100% silicone meets the above requirements and functions far better than an acrylic latex or siliconized acrylic caulking since the 100% silicone remains flexible. As seen in the above photo, the 100% silicone remains intact and shows no visible signs of losing its bond to the tile edge after being flexed about thirty degrees. However, the siliconized acrylic caulking broke loose from the tile edge after bending the joint in a similar fashion just once and failed.

While 100% silicone may be more expensive than the lesser performing caulking, it is money well invested since it eliminates failure and a costly callback from the consumer.