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Thinset for Stone Veneer Installations Explained

If you wonder into your local home improvement or discount tile and flooring store to pick up supplies for your next tile or stone veneer project, you’ll likely find yourself at some point in the setting materials aisle confused by what you’re seeing. There’s thinset, mastic, mortars, epoxies, and additives that are available in a different variety of formats like pre-mixed and bucketed, powder and liquid. Some products are polymer modified, others have or require a latex additive. What does all this mean, and what is the right product for a stacked stone tile installation? Let’s take a look at these different types of setting materials and learn more about what each type is best suited for.

Thinset for Stone Veneer with Trowel

Thinset mortar is a blend of cement, very finely graded sand, and a water retention compound that allows the cement to properly hydrate. Tile and stone set by the thinset method is adhered to the substrate with a thin layer of “thinset” cement. The terms thinset cement, thinset mortar, dryset mortar, and drybond mortar are synonymous. This type of cement is designed to adhere well in a thin layer - typically not greater than 3/16th thick.

Within the thinset mortar category, you’ll likely come across unmodified, latex, and polymer varieties. Unmodified thinset has limitations as it relates to what kind of substrate it can be applied over, whereas the latex and polymer varieties have had special chemicals added to them which improves certain characteristics of the setting material, most often freeze/thaw resistance, improved flexibility, and improved adhesion to a variety of different substrates.

Thinset is packaged in a variety of different methods, depending on the manufacturer. Some brands offer a dry pre-mixed version of either latex or polymer modified thinset which just requires the installer add water to the mix. Other manufacturers sell the latex or polymer modifiers in liquid format, and the installer will add the “modifiers” to regular thinset to create a latex or polymer modified variety. You’ll even find some premixed and bucket thinsets, which can be good for small projects but tend not to make economic sense for a large project. Whatever packaging method you choose for your next stacked stone installation project, be sure to read the manufacturer’s instructions to make sure you’ve purchased the right mix or combination of materials to achieve the desired thinset for your project.

Mixing Thinset for a Stone Veneer Installation

Epoxy thinset will come in buckets which normally require mixing of the resin, hardener, and powder to “activate”. Epoxy thinset is extremely strong and versatile, bonding nicely to a variety of different substrates, including metal, and is also impervious to water, making it a good choice for exterior or moisture heavy applications. The main drawback with Epoxy thinset is that it is far more expensive than standard thinset, can have a powerful odor when working with it, and sets very quickly, making it harder to work with for an installer not familiar with the product.

Mastic is another related setting material product that you’ll find in the thinset aisle. Mastic will normally come in bucketed forms, making it tempting for many tile installers that don’t want to mix their own setting materials, however mastic has a number of drawbacks. The product itself is organic, made from the resin of the mastic tree. The organic make up of this product makes it inappropriate to used in any application where it will be exposed to moisture – where the adhesive will re-liquify and lose its adhesive strength. Mastic can also grow and harbor mold, making it a product to avoid at all costs on any installation that might be subject to moisture.

Mortar is generally something that doesn’t get used to install tile and stone, especially for wall applications. It’s a good deal less expensive than any variety of thinset, but doesn’t have the same “grip” strength or holding power and can be more susceptible to substrate movement and freeze / thaw cycling. Mortar is more commonly used in concrete block construction, although some “old school” installers will use mortar for stone masonry work.

So with all these choices, what is the best setting material for stacked stone installations? The answer – polymer modified thinset. These thinsets are independently lab tested to verify they have a high shear bond strength to keep heavy split face stone from falling off your walls, will work on a variety of substrates, and most will be rated for freeze/ thaw and outdoor / submerged applications. We always recommend our customers look for thinsets that meet or exceed ANSI A118.4 and ANSI A118.11 testing procedures which ensures the thinset will create a strong bond with the cementious substrate and hold the stone tightly to the wall.

DIY Network Host installing Norstone Stone Veneer using Thinset

When considering what tile thinset to buy, we also recommend our customers look at what the manufacturer offers in terms of a system warranty. Many setting material manufacturers have worked with tile and stone manufacturers to write a formal specification sheet and warranty program which warrants the installation of the material when the spec is followed and that manufacturer’s products are used. There is very little that can go wrong with stone or tile assuming the right product has been selected for the application, so most manufacturers do not have any form warranty on the material itself – however the installation can certainly fail if done improperly or with the wrong materials, so the system / installation warranty is a great thing to have for your next tile or stone project.

Our final recommendation on this topic is to visit your local tile and stone shop to purchase setting materials. Wherever you ended up sourcing your tile and stone from, purchasing the setting materials from a reputable tile and stone dealer in your local market is always going to be a great idea. You’ll get expert advice on what setting material will work best from your product and many times have access to different manufacturers and price points then you’ll get at the big box home improvement stores who typically only carry one or two manufacturers.

Setting materials are too important to a successful stone veneer installation than to guess at what the right product is for your installation. Any of the expert reps at Norstone are happy to answer your questions, look at the specs of a product to confirm it’ll work, or make specific recommendations on products to use for your next project. So next time you’re getting ready to buy setting materials for your next tile or stone installation show that aisle who’s the boss and pick the right material the first time.

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Norstone's New Dimensions in Natural Stone blog aims to discuss design themes, sources of inspiration, and how the world around us influences our creative interpretation and buying preferences.

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