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Applying thinset mortar over dark adhesive is generally not recommended due to several factors that can affect the performance and longevity of the tile installation.
1. Lack of Bonding:
Dark adhesives often have low porosity and may contain additives that hinder the bond between the tile and the thinset mortar. This inadequate bonding can lead to tiles becoming loose or even dislodged over time.
2. Moisture Issues:
Dark adhesives, especially those that are water-based, can prevent proper moisture evaporation. This trapped moisture can cause several problems, such as mold growth, tile discoloration, and adhesive breakdown. Applying thinset over dark adhesive exacerbates this issue as it further restricts the escape of moisture, potentially leading to long-term damage.
3. Adhesive Compatibility:
Another concern when considering applying thinset over dark adhesive is the compatibility between the two materials. Different adhesive formulations may have chemical components that react negatively with thinset mortar, affecting its setting time or adhesive properties.
Alternative Approaches:
Instead of applying thinset mortar directly over dark adhesive, it is advisable to remove the old adhesive before proceeding with tile installation. This can be done through mechanical means, such as scraping or sanding, or by using adhesive removers available on the market. By ensuring a clean and smooth surface, you can create a suitable base for the thinset mortar to bond effectively with the substrate.
While it may seem tempting to apply thinset mortar directly over dark adhesive to save time and effort, it is not advisable due to factors such as inadequate bonding, moisture issues, and concerns about adhesive compatibility. When undertaking a tile installation project, it is crucial to prioritize the long-term durability and stability of the installation. By properly preparing the surface and using the right materials, such as removing the dark adhesive, you can ensure a successful tile installation that will stand the test of time.