Should I use 100% Silicone Caulk Sealant or the Sanded Caulk Sealant?

QUESTION

I have a white subway tile backsplash in my kitchen, counter is granite. Should I use 100% silicone caulk between the two or can/should I use a sanded silicone caulk by the same manufacturer??

ANSWER

ANSWER - The tile and stone industry standards require that an ASTM C920 sealant (caulk) is used for movement joints and transition joints between changing planes or materials.  ASTM C920 are normally 100% silicone or a urethane sealant.

Sanded sealants (caulking) normally do not meet ASTM C920 standards nor do they perform as well or last as long.  Typically sanded sealants are acrylic or latex based and they might say it is siliconized, which is not the same as being 100% silicone.  They are much easier to use for the installer in terms of application and installation, but they don't come close to lasting as long or performing as well.  Installing the 100% silicone sealants requires much more protection and care, and timing of the application is critical to ensure a good installation and easy cleanup.

I have seem some installers broadcast sand over the 100% silicone so it looks more like the grout, but that diminishes the performance of the material and voids the product warranty.

Note that per the sealant directions you are suppose to apply a backer rod or backer tape in the movement joint before applying the sealant, and the sealant needs to be at least 1/4" thick for walls, which isn't practical for very thin tiles.   Per sure to follow the sealant manufacturer's directions.

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