Outdoor Tile Adhesives

Modified Thinset Mortar the Right Choice for Patios

Tile on patio
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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 outdoor tile adhesive. There are many types to choose from. It is important to pick the right one. For an outdoor patio, you will almost always use a modified thin-set mortar for an adhesive.

Buying and Using Outdoor Tile Adhesives

Many homeowners are afraid to take on a DIY landscaping project of this sort, because buying the right products -- and then using them properly -- seems like a daunting task.

I hope that reading the information below will assure you that this is, indeed, a job that you are capable of undertaking. I will set your mind at ease by posing -- and answering -- four questions.

Question 1: What is a modified thin-set mortar? It is mortar made with Portland cement, fine sand, water, and latex additives. Unmodified thin-set does not 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.

Question 2: Where would you buy this type of tile adhesive? Modified thin-set mortar can be purchased at most home improvement stores (Home Depot, Lowes, etc.) and tiling shops. Be sure to tell the sales representative that you are undertaking an outdoor project so he or she can recommend the proper tile adhesive product. I do not recommend mastics and other premixed tile adhesives for use outdoors.

Question 3: How much tile adhesive do you need to buy? Thin-set  mortar comes as a dry mix, usually in 50-pound bags. Smaller bags are sometimes available, as well. 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.

Question 4: How do you mix thin-set mortar? You will need an electric drill and a paint paddle/mixer. Most modified thin-set mortar products 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 thin-set 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 the frosting you would find on a cake.

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