EN 12004 classifies tile adhesives by type and performance. The first letter is the type: C for cementitious, D for dispersion and R for reaction resin. The number is the class: 1 for normal and 2 for improved adhesion.
- F: fast setting.
- T: reduced slip, for walls.
- E: extended open time.
- S1 and S2: deformable and highly deformable.
A C2TE S1 adhesive is thus an improved, slip-resistant, deformable cementitious adhesive with extended open time. Porcelain, with its very low absorption, generally needs a class 2 adhesive.