Last Updated: , Created: Tuesday, February 10th, 2004

Applying tile adhesive correctly

I recently spent some time at the Terrazzo, Tile and Marble Association training centre in Toronto and learned some very basic but surprising things, like just how to apply tile mastic and why it makes a difference.


Using a notched trowel gives you a measured quantity of mastic or thinset mortar that is evenly applied across a surface. The reason for the little ridges in the trowel is to give you the exact thickness of adhesive or mortar required for each application. That is why each adhesive or thinset has instruction on exactly what tooth design you need on your trowel.





In fact the idea is that when the ridges created by the trowel are squashed down and all the air eliminated, you should have exactly the thickness of adhesive that particular material requires. That explains why some patterns deposit more adhesive than others.






But -- the great big but is -- did you get out most of the air? We can see the problem best with my transparent tiles. If you draw out the trowel lines rather straight, the air gaps stretch right across any given tile, letting the air escape out both ends as the tile is pushed into place, as in the second photo above. The third photo shows pretty even coverage and good tile support.





When you make tight swirls with your trowel you may not think it will make any difference, but if the swirls trap air pockets as in the photo, the tile will ride high and there will be less surface coverage with the adhesive.







The side-by-side tiles in the last photo will not sit the same, nor have the same durability on the floor.     The adhesive lines don't have to be absolutely straight, nor all go in the same direction, but they should be rather straight across a single tile.





One other tip I wanted to pass on. If you set a tile into its adhesive and then slide it toward another tile to adjust the position, you push up adhesive between the two tiles which can give you problems with good grout coverage. Place a tile close to its neighbours and then slide it slightly away from them to the correct position -- that will avoid an adhesive build-up between tiles.



Keywords: Floors, Adhesive, Mortar, Tiles, Tip, Techniques

Article 2002