Slate Tiles have not set on the tiles adhesive

We laid half a floor of tiles yesterday only to find this morning that many had not "set" ie they were not attached to the adhesive.

What have we done wrong?

Hello Sandi

Adhesive not setting can happen for a number of reasons. It may be the case that too much water has been added or the room itself is cold.

Adhesive open times are governed by temperature and depending on where it is being used or if you have a batch made several months ago. This can vary the open time considerably.

Correct application with a notched trowel is also a factor. If a notched trowel has not been used then again the correct bond required has not been made between adhesive and tile.

Another reason could be if you have trafficked the area before the set time of the adhesive then you could have sheared the bond causing the tile to come away clean from the floor. Has this happened all over or just in trafficked areas.