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Outdoor Tile Adhesives

Modified Thinset Mortar a Good Choice for Patios


When you are ready to begin setting tiles for your new patio, that is, bonding them to the concrete slab, you need to use the appropriate tile adhesive. With many to choose from, it is important to pick the right one. For an outdoor patio, you will almost always use a modified thinset mortar for a tile adhesive.

What is a modified thinset mortar? It is mortar made with Portland cement, fine sand, water and latex additives. Unmodified thinset doesn't have the latex additives. We want the additives for our outdoor patio because they help reduce water absorption, improve the strength of the bond, and minimize movement due to changes in temperature.

Where to buy this type of tile adhesive. Modified thinset mortar can be purchased at most home improvement stores and tiling shops. Be sure to tell the sales representative you are undertaking an outdoor project so they can recommend the proper tile adhesive. I don't recommend mastics and other premixed tile adhesives for use outdoors.

How much tile adhesive do you need? Thinset comes as a dry mix, usually in 50-pound bags. Smaller bags are sometimes available too. Check the coverage chart on the back of your bag to determine how much tile adhesive you need. On average, a 50-pound bag covers 60-100 square feet.

How to mix thinset. You will need an electric drill and a paint paddle/mixer. Most thinsets are mixed with water. Some are mixed with a latex liquid instead. Always check the directions on your bag. To mix with water:

  1. Pour about 2 inches of clean water into a 5-gallon bucket.
  2. Dump a small amount of the thinset powder into the bucket.
  3. Thoroughly mix the water and powder. Add more water or powder as necessary to create a paste with the consistency of frosting.

Each type of tile adhesive can have a different mixing procedure. Some need to be mixed, allowed to sit for ten minutes, and then mixed again. Your bag of thinset should have mixing instructions on it. Follow them explicitly for the best results.

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