Thinset, also known as thin-set mortar or simply mortar, is a type of adhesive commonly used in the installation of tiles, stone, and other materials in pools. It is a mixture of cement, sand, and water-retaining additives that provide a strong and durable bond between the substrate and the surface material.

In this article, we will discuss the different types of thin-set for pools, their characteristics, and how to choose the right one for your project.

Types of thinset for Pools

There are two main types of thinset used for pools: modified and unmodified. Modified thinset contains additional additives such as polymers or latex, which improve its flexibility, strength, and water resistance. Unmodified thinset is a simpler mixture of cement and sand, without any additional additives.

Modified thinset is the most commonly used type for pool installations due to its superior properties. It is suitable for a wide range of surfaces, including concrete, cement board, and fiberglass, and can be used for both interior and exterior applications. Modified thinset is also recommended for use with large-format tiles or in areas with high levels of moisture.

Unmodified thinset is typically used in situations where there is no risk of moisture infiltration, such as indoor pool installations or above-waterline tile installations. It is also recommended for use with natural stone tiles or other sensitive materials that may be damaged by chemicals in modified thinset.

Characteristics of Thinset for Pools

When selecting thinset for pool installations, there are several important factors to consider:

Water Resistance:

Thinset used in pools must be able to withstand constant exposure to water and chemicals without deteriorating. Modified thinset is typically more water-resistant than unmodified thinset.


The thinset must be able to withstand the movement and expansion caused by changes in temperature and humidity. Modified thinset is more flexible than unmodified thinset, making it a better choice for pool installations.

Bond Strength:

The thinset must provide a strong and durable bond between the substrate and the surface material. Modified thinset is typically stronger than unmodified thinset.

Setting Time:

The time it takes for the thin-set to set and cure can vary depending on the type of thin-set and environmental conditions. Modified thin-set may have a longer setting time than unmodified thinset.

Choosing the Right Thinset for Your Project

When choosing thin-set for your pool installation, it is important to consider the specific requirements of your project. Here are some tips to help you select the right thin-set for your needs:

Consult with a Professional:

If you are unsure about which type of thin-set to use, consult with a professional installer or supplier. They can help you select the right product for your specific application.

Consider the Substrate:

The type of substrate you are installing the tiles on will affect the type of thin set you need. For example, fiberglass pools may require a different type of thin-set than concrete pools.

Check the Manufacturer’s Recommendations: Always follow the manufacturer’s recommendations for the type of thin-set to use with their tiles or other materials.

Consider Environmental Conditions:

Environmental conditions such as temperature, humidity, and exposure to sunlight can affect the performance of the thinset. Make sure you choose a product that is suitable for the specific conditions of your project.

Choose a High-Quality Product:

When it comes to thin-set for pools, quality matters. Choose a high-quality product from a reputable manufacturer to ensure a strong and durable bond.


This set is an essential component of any pool installation project. By choosing the right type of thin-set for your project and following best practices for installation, you can ensure a long-lasting and beautiful pool surface. Whether you choose a modified or unmodified thin-set, make sure to consider the specific requirements of your project, such as water resistance, flexibility, bond strength, and setting time.

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