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Thinset Quick Start Guide


Thinset is a great waterproof adhesive. Tile setters for over 125 years have been using this material to install ceramic tile PERMANENTLY.

Why is thinset so fantastic? It’s simply Portland cement and fine silica sand. Sometimes there might be another additive in the blend to increase strength.

Portland cement is the only thing that holds sand and rock together in most concrete you walk or drive on, so you KNOW it’s strong and waterproof.

I’ve rated this guide two hammers out of five because it’s really simple to work with thinset. It would rank just one hammer if it wasn’t so heavy!

The most important thing to realize when working with thinset is water is both your friend and foe. You need water to mix thinset and make it just right, but TOO MUCH water - or adding water if it gets stiff - can RUIN the thinset!

Watch the video below unless you’ve come here from YouTube having already watched it.

Be sure to look at the RELATED CONTENT links at the bottom of this page. Lots of goodies there for you.


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  • STOP AND READ all the mixing and safety instructions that you see on the bags of thinset. Seriously, read them. Follow the instructions.
  • Thinset, once mixed, should resemble warm cake icing. Not too thin, but thin enough it’s pourable or it falls off the mixing knife.
  • Only mix enough thinset as you can use in 15 or 20 minutes.
  • Knee pads! Wear great knee pads or a use a cushion.
  • Use a crack-isolation membrane under the thinset, when possible, to prevent cracks.
  • Use a damp sponge to get up every speck of dust from concrete slabs or other subfloor. You’ll get better bonding.
  • Apply the thinset to damp concrete or subfloor for BEST bonding.
  • Use the proper sized notched trowel for the ceramic tile you’re installing!
  • The floor should be FLAT for best results. Fill in low spots or use a self-leveling compound.
  • If the thinset pulls up as you trowel and you don’t get completely filled or solid lines of thinset when using the notched trowel, it means you’ve got DUST on the floor or the thinset is too dry.
  • If it’s hot and dry where you’re working, use COLD water to mix the thinset. This will help retard the hydration reaction allowing you some extended work time. Use ICE in the water if necessary to get it COLD.
  • Do NOT retemper (retemper means add water and stir) the thinset if it gets stiff in the mixing bucket. If you add water to stiff thinset to make it workable, you break the microscopic Portland cement crystals and the thinset will NOT be as strong as it could be. This is why you only mix as much as you can use in a short time.
  • Celebrate your Victory!

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2 Responses to Thinset Quick Start Guide

  1. Thinset is NOT waterproof! Giving bad advice to unsuspecting homeowners is terrible specially since your site is called ask the builder! Please stop giving tile advice if you do not know about the products being used, it hurts my industry and people start to distrust tile as a long lasting covering. Thank you

    • Jeremy,

      Oh I'm so sorry to embarrass you in public, but we need to STOP people like *you* from giving out bad advice.

      Do you know what the ingredients are for thinset?

      I'll share them:

      Portland cement
      silica sand

      Do you know the definition of waterproof?

      Here's one:

      "impervious to water: a waterproof hat.
      • not liable to be washed away by water: waterproof ink."

      After thinset hardens, water does not dissolve it.

      Water does not cause it to lose its bond between the tile and the substrate.

      Thus, it's *waterproof*.

      What makes you think it's NOT waterproof?

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