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Tile Adhesives

Tile Adhesives - Mastic vs Mortar

Choosing the best tile adhesive can be difficult with all of the available options today. To install tiles properly, one must understand the basic characteristics of the tile being installed and the surface, or substrate, onto which the tile is being installed. Common tile adhesives in use today are mastic and thinset mortar.

What is Mastic?

Mastic is a high-strength, organic adhesive used in construction. It is available as a thick, glue-like liquid in pails or caulk tubes. Installers have historically used mastic for ceramic wall tile installation due to its high level adhesion. Compared to some thinsets, mastic has a superior holding strength and it is easier to apply. Mastic has several major drawbacks when used as a tile adhesive. It is not recommendeded for use in any environment that is exposed to moisture. Being organic, mastic becomes prone to mold growth once it encounters moisture. Mastic also cannot be "built up" like a thin-set mortar, making it more difficult to deal with minor substrate imperfections.

What is Thinset Mortar?

Thinset mortar is made of Portland cement, fine sand and moisture-retaining agents. Thinset is resistent to mold and moisture and it will not shrink or contract. You can find it in most hardware stores labeled as "thin set cement", "thin-set mortar", or "dryset mortar". Thinset is applied using a notch trowel. Depending on your application and the size of your tile, you may need a 'medium-bed' thinset which is used for large, heavy tiles.

Standard vs Pre-Mixed Thinset

Standard thinset is sold as a powder that needs to be mixed with water to activate. Pre-Mixed thinset comes ready-to-use in a pail and is generally more expensive. The convenience of pre-mixed thinsets are good for small areas or DIY project while standard thinset is the preferred option for most professionals.

Modified vs Unmodified Thinset

Unmodified thinset is comprised of Portland cement, sand, and a water retention agent. Modified thinset contains an additional polymer which improves bond strength and other characteristics like working time, the time between initially mixing thinset and it becoming unusable due to curing. It is important to refer to manufacturer recommendations for each product you are using. Specialty tile manufacturers usually provide information about recommended adhesives.

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