Choosing the Right Outdoor Tile Adhesive

Tile on patio

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When planning to set outdoor tiles, like on a concrete slab for a patio, you will need an appropriate outdoor tile adhesive to withstand the test of time and the harsh elements. There are many bonding materials, from modified to unmodified thin-set mortar and mastic to a polyurethane-based construction adhesive. Read on to find the best outdoor tile adhesive for your next outdoor tile project.

Buying Tile Adhesive

Many homeowners are afraid to take on a DIY patio project because buying the right products—and then using them correctly—seems like a daunting task. For an outdoor patio, you will almost always use a modified thin-set mortar for an adhesive.

Modified thin-set mortar attaches tile or stone to surfaces such as cement or concrete. The additives in the "modified" thin-set will help it withstand weathering and time. Adhesive materials like mastic or unmodified mortar do not the additives that resist water and temperature fluctuations.

A modified thin-set has more cement and polymers, helping it perform better. You can pay anywhere from $10 to $25 per 50 pounds. Depending on the tile application, 50 pounds can cover 25 to 50 square feet for a unique tile or special pavers that require a thicker application; or if you add straightforward mosaic porcelain tiles, 50-pounds can cover 200 square feet.

Another standard adhesive that is used for outdoor tiling projects is PL adhesive. It is a polyurethane-based, moisture-curing adhesive that is much stronger than ordinary construction adhesives. PL adhesive is pricey compared to thin-set, costing about $10 for a 28 oz. tube. It's best used to fix tiles that come loose or, if you are tiling a small, custom project.

What Is a Modified Thin-set Mortar?

It is a mortar made with Portland cement, fine sand, water, and latex additives. Unmodified thin-set does not have latex additives. The additives help reduce water absorption, improve the strength of the bond, and minimize movement due to temperature changes.

Where Would You Buy This Type of Tile Adhesive?

You can purchase modified thin-set mortar 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 they can recommend the proper tile adhesive product. Steer clear of mastics and other premixed tile adhesives for use outdoors.

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 to 100 square feet—but the project and tile type can affect how thickly you need to apply the adhesive.

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 combined 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 frosting consistency you would find on a cake.

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

Popular Brands

The most common adhesive brands available in the U.S. for outdoor tiling projects include:

  • Versabond: High bond strength, all-purpose, polymer-modified mortar adheres to most surfaces; used indoors and outdoors; can also set in cold weather
  • Laticrete 254: Polymer-fortified, thin-set mortar for interiors and exteriors; useful for thin porcelain tiles, thin porcelain tile panels, and glass tiles; bonds to exterior glue plywood and concrete
  • Loctite PL Premium: This modified thin-set mortar alternative also goes by LePage PL Premium in Canada. This polyurethane-based construction adhesive works very well in all outdoor conditions. It comes in a caulking tube; it's thick—a good consistency for setting tiles.