Self-leveling concrete is a popular material used for smoothing and leveling uneven concrete surfaces. It is commonly used in both commercial and residential applications to provide a smooth and level base for various types of flooring installations. However, when it comes to applying self-leveling concrete on thinset, there are a few important considerations to keep in mind. In this article, we will explore whether or not self-leveling concrete can be applied on top of thinset, highlighting the potential issues and providing suitable recommendations.
Understanding Self-Leveling Concrete and Thinset
Before delving into the compatibility between self-leveling concrete and thinset, let’s first understand what each material is and their primary functions.
Self-leveling concrete:
Self-leveling concrete is a mixture of cement, sand, and special additives that enable it to flow and level itself, creating a smooth and even surface. It is typically used to correct uneven, rough, or damaged concrete surfaces before installing flooring materials.
Thinset:
Thinset, also referred to as mortar, is a cement-based setting material used for attaching tiles, natural stones, or other finishes to a substrate. It acts as an adhesive and provides a strong bond between the surface and the flooring material. Thinset is often used in tile installations or as an underlayment for tile and stone floors.
Compatibility Issues
While self-leveling concrete and thinset serve different purposes, they can sometimes interact in a way that hinders their compatibility. The main compatibility issue arises due to the composition and chemical reactions of these two materials.
Bond Strength:
Thinset requires a rough and porous surface to create a proper bond. However, self-leveling concrete creates a smooth and non-porous surface. This difference in surface characteristics can weaken the bond between thinset and the self-leveling concrete, leading to delamination or lifting of the tiles or finishings.
Drying Time:
Thinset usually takes longer to dry compared to self-leveling concrete. Applying self-leveling concrete over thinset can impede the drying process of the thinset, causing it to dry unevenly or taking an extended period to cure. This can compromise the overall integrity and strength of the installation.
Recommended Solution: Removing Thinset or Utilizing a Primer
Considering the compatibility issues mentioned above, it is generally not recommended to apply self-leveling concrete directly on top of thinset. However, there are two potential solutions to mitigate these issues:
1. Removing Thinset:
If the existing thinset layer is thin or if it can be effectively removed, it is advisable to remove the thinset completely from the surface. This will ensure a proper bond between the self-leveling concrete and the substrate, creating a more stable and durable installation.
2. Utilizing a Primer:
An alternative solution is to use a primer before applying self-leveling concrete. Primers create a bonding layer between the existing thinset and the self-leveling concrete, enhancing the adhesion and promoting a stronger bond. A primer specifically designed for this purpose should be applied following the manufacturer’s instructions.
While self-leveling concrete is a versatile material for leveling uneven surfaces, it is not recommended to apply it directly on top of thinset due to compatibility issues. The difference in surface characteristics and drying time can compromise the bond strength and overall integrity of the installation. Therefore, it is advisable to either remove the thinset or utilize a suitable primer before applying self-leveling concrete. By following these recommendations, you can ensure a successful, long-lasting flooring installation.