What You Need to Know About Thinset or Mortar

What You Need to Know About Thinset or MortarDo you know the difference between thinset or mortar and grout? Both are critical, but they each play different roles in a tile installation.

What is Grout?

As we explained in Why You Need Grout When You Install Tile and Stone, grout is used as a filler for the joints between tiles once the tile you are installing has been set. Most grouts are a powdered mix of cement, lime, color pigment and sometimes sand that hardens when mixed with water and left to cure.

Grout gives your floor or wall a crisp finished appearance. It helps keep dirt and debris from getting in between and under your tile and it adds rigidity and strength to the tile installation.

>> Also see Frequently Asked Questions About Grout

What is Thinset or Mortar?

Thinset, on the other hand, is used to install tile over cement, cement/fiber board and anti-fracture/water proofing membranes. It is what makes it possible for tile or stone to stick or bond to the backer board.

Thinset or mortar (or thinset mortar, thinset cement, dryset mortar, or drybond mortar) is an adhesive made of cement, fine sand, and a water retaining agent such as an alkyl derivative of cellulose. Many thin-sets have latex and polymer additives in them designed to increase bonding strength.

As tile sizes get larger and longer, adequate mortar coverage becomes increasingly critical.

An exception to thinset and grout being distinct: Integra

An exception to thinset and grout being distinct: Integra

For the most part, thinset or mortar have nothing to do with grout -- except for one product: Integra.

Integra is a nonabrasive all-in-one adhesive and grout for glass tile installations on walls and floors. It was developed especially for the installation of mosaics and glass tile of all shapes and sizes with no concerns about thin set color bleed through because the adhesive and the grout are the same color.

It's available in eight Merkrete colors.

>> See Merkrete Duracolor Grout and Integra Thinset Adhesive and Grout

Which thinset should be used for which type applications?

Don't assume that any thinset will do for your tile installation project. You see, based on the characteristics of your individual project, you'll find that there is a specific thinset to use for that application.

We definitely recommend that you speak to a Tile Outlets of America sales representative and explain the project details, including  any materials being used and we will help you select the correct product.

Tip: Merkrete has a very useful app you can download to your phone. It will give you helpful specifications not just on the specific thinset or mortar to use, but also the substrate it can be installed on and any other information you would like to know. The information is far more extensive than what you find on the back of the thinset bag.

>> See How To Set Large Format Wall and Floor Tile: Merkrete Demonstration

  • For all Schluter products, a premium un-modified thinset should be used.
  • For rectangular plank tile , use a medium bed mortar such as 720 marble pro.
  • A light weight thinset is commonly used on walls.
  • Light weight thinset - such as Merlite 820 - is less likely to sag if used properly.
  • For most installations a modified thinset such as the 703 or 710 is recommended.

Don't forget to select the correct trowel size!

Make sure to select the correct trowel size for your project.

You'll want to use a smaller trowel for small tile and a larger one for large tile. Use a trowel that will help you achieve a continuous minimum 3/32” coverage.

Larger tiles most often require deeper notched trowels.

>> See 9 Top Questions About Trowels

Make sure to select the correct trowel size for your project.

How should you mix thinset?

In many ways, you'll want to mix thinset the same way you mix grout: pay close attention to the manufacturer's instructions.

Always double check the manufacturer's instructions on the tile you purchase for exact product requirements and installation guidelines.

You need to use the appropriate thinset mixing paddle.

Thin-set should be mixed to the consistency of peanut butter. While specific instructions vary by manufacturer the basics are the same.

  • Dry thinset and water should be mixed in a bucket in stages.
  • A whole bag should never be mixed at one time.
  • Add about half of your water to the bucket, then add some thinset and mix.
  • Keeping adding thinset until you reach the correct consistency.
  • Let the material slake and then remix and you are ready to go.

Due to its cement ingredients, thinset should be made up in small batches as needed. It also should never be washed down a drain, as it will harden in your pipes.

How should you apply thinset or mortar?

When spreading thinset, don’t spread any more on the floor or wall than you can work in a few minutes. Thinset dries very quickly once it’s troweled out.

Proper mortgage coverage is critical to preventing failures.  According to the ANSI and the TCNA Handbook, tile requires a minimum of 80% mortar coverage in interior applications, and 95% for exteriors and wet environments. Natural stone tile requires 95% coverage in all areas.

Mortar coverage becomes particularly important as tile sizes get larger and longer (think wood plank tile). This applies to any tile with any side 15 inches or longer. What seems to work for small tiles no longer works.

>> See An Introduction to Tile Warpage and the Role of Mortar

As a recap, be sure to:

1. Prep your installation surface so it is flat.

2.  Make sure that you get proper mortar coverage on the tile. Start by keying the thinset in to the substrate using the flat side of the trowel. (Keying or burning in allows the tile mortar to bond better with the substrate by increasing your bond to the pores or texture of the substrate. Hold the flat side of your trowel at 45 degrees to the substrate and pull towards your body changing direction with each pull leaving a thin layer behind.)

3. Don't swirl the mortar!

4. "Play it Straight!" Comb the mortar in straight lines

5. Backbutter the tile

6. Move the tile in one direction to collapse the mortar ridges

7. Trowel size matters

8. Don't ever spot bond tile!

>> See How To Install Tile Correctly and Get Proper Mortar Coverage

What questions about thinset or mortar do you have?

Let us know if we've missed a question you have about thinset or mortar and we'll add it to this article.

Or, simply visit us in-store and ask us. We look forward to seeing you at Tile Outlets of America!


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