Recent advances in grouts and adhesives are what make the Shutterstile concept possible. Traditional grouts and adhesives just can't stand up to weather extremes without cracking or failing completely. But a few companies have now developed flexible, weather resistant alternatives designed to join dissimilar materials and to stand up to harsh climates. We use a polymer adhesive and urethane-based grout. Because of the high cost of these materials, you aren't likely to find them in use by your local tile setter. And they probably aren't cost-effective for most tiling situations where traditional materials are adequate. But they are just the thing for the high end look of a Shutterstile shutter.