Yes, you can add sand to tile adhesive, but it is generally not recommended and will likely weaken the bond.
While it might seem like a way to thicken the adhesive or stretch the material, introducing sand, especially common types like red builders sand, has significant drawbacks that negatively impact the performance of the tile installation.
Why Adding Sand is Problematic
According to the provided reference:
- Coloration: Adding materials like red builders sand will colour the adhesive. This can affect the finished look, particularly if the adhesive is visible in grout lines or through translucent tiles.
- Altered Consistency: Adding sand will thicken the “glue layer”. While this might seem beneficial for filling gaps, it changes the fundamental properties of the adhesive.
- Weakened Bond Strength: The reference explicitly states that adding sand means the bond strength becomes more about cohesive strength (glue to glue), than glue to tile (adhesive strength). Essentially, the sand particles interfere with the adhesive's ability to grip the tile and the substrate effectively.
- Overall Weakening: The addition of sand leads to a weakening of both bonds (glue to tile and glue to itself). This compromises the stability and durability of the tiled surface.
Consequences of Using Sanded Adhesive
Using tile adhesive that has been mixed with sand against manufacturer recommendations can lead to various issues down the line, including:
- Tiles becoming loose or detaching over time.
- Cracking in the grout or tiles due to insufficient support.
- Failure of the entire tiled area, especially in areas subject to moisture or traffic.
Tile adhesives are scientifically formulated to provide specific adhesion properties and work best when mixed and applied according to the manufacturer's instructions. They contain carefully balanced polymers, binders, and fillers to create a strong, durable bond between the tile and the substrate. Adding foreign materials like sand disrupts this balance.
In summary: While physically possible to mix sand into tile adhesive, it's a practice that degrades the adhesive's performance and weakens the crucial bond needed for a successful and long-lasting tile installation.
