Tile adhesive height depends on how thick you apply it. Trowel notch sizes vary between 4mm and 20mm. If the trowel has a 10mm square notch, you can expect a compressed adhesive height of 5mm (half the notch height). If the trowel has an 18mm U-notch, you can expect a compressed adhesive height of 6mm (one-third of the notch height).