What Are the Grades of Porcelain Tiles
PEI & Tile Classes Explained
When you search online or ask your contractor about tile quality or grades, the first thing that comes up is the PEI rating. Everyone tells you to buy a PEI 4 or PEI 5 tile.
But once you start digging deeper, you quickly realize that everyone is telling a different story.
We’ll Begin by Explaining What’s PEI
- Class 5: Heavy Commercial: suitable for intense commercial and all residential.
- Class 4: Commercial: suitable for medium commercial and all residential.
- Class 3: Heavy Residential, Light Commercial; suitable for all residential, average abrasion.
How Tiles Are Classified
European standard EN 14411 and ISO 13006:2012 establishes a classification based on:
1) Forming method, assigning code A for extrusion and B for semi-dry pressing. (A is not superior to B)
- Extruded tile: shaped in the plastic state in an extruder, cut into tiles of predetermined dimension and designated as group A.
- Dry-pressed tile: formed from a finely milled body mixture and shaped in molds at high pressure and designated as Group B.
“All interior and exterior wall and floor tiles we typically deal with are dry-pressed, except porcelain slabs, which are extruded.“
2) Water absorption capacity (E),
| Extruded Tiles | Dry Pressed Tiles | |
| AIa (E ≤ 0.5%) | BIa (E ≤ 0.5%) | Porcelain Tile |
| AIb (0.5 < E ≤ 3%) | BIb (0.5 < E ≤ 3%) | Hard Ceramic Tile |
| AIIa (3<E≤6%) | BIIa (3<E≤6%) | Subway Tile |
| AIIb (6<E≤10%) | BIIb (6<E≤10%) | White Body Wall tile |
What Are These Numbers For
These numbers refer to the water absorption rate (E) of the tile. In simple terms, they tell you how dense the tile is and where it can be used.
Porcelain alone is a high-quality product. As long as you make sure that your tile is a dry pressed ceramic tile with water absorption E ≤ 0.5%, it meets the requirements for residential floors.’A glossy tile is not mechanically polished. If your tile falls into (0.5 < E ≤ 3%), it belongs to group BIb. This means it is not porcelain but a ceramic tile with relatively low water absorption. Glossy tile is not a bad product — it is simply not porcelain.
As water absorption increases:
- (3% < E ≤ 6%) – BIIa → standard ceramic tile (many subway tiles fall here)
- (6% < E ≤ 10%) – BIIb → typical wall tile
Lower absorption = denser tile = suitable for floors and heavy use.
Higher absorption = lighter, more porous tile = suitable for walls.
Therefore, when grouping dry pressed tiles, what matters is not the name (porcelain, ceramic, glossy), but the water absorption value (E) and how it aligns with the intended use.
Tiles may be glazed (GL) or unglazed (UGL); they are incombustible and are not affected by light.
What is Glaze
Glaze is a vitrified (glass-like) coating applied to the surface of a tile. Once fired, it becomes impermeable, meaning it does not absorb water.
The tile’s base color and design are part of the tile body or applied before glazing. The glaze sits on top and acts as a protective layer, while also controlling the final finish (matte, glossy, textured).
Unglazed Tiles
When the design and color run through the entire thickness of the tile, it is called a through-body tile.
When the design and color partially extend into the tile body, it is called a double-charged tile.
Because there is no glaze, the surface does not wear off. This gives unglazed tiles high resistance to abrasion, scratches, and heavy traffic. They also offer high mechanical strength.
However, unglazed tiles do not have the protective barrier of a glaze. For this reason, they are typically produced with very low water absorption (porcelain level) to reduce staining and improve performance.
Even though through-body and double-charged tiles carry high technical specifications, they must be selected carefully. Unglazed tiles from unknown or low-quality sources may be more prone to staining and surface issues.
What is Colored-Body Tile
A colored-body tile is a porcelain tile where the porcelain body of the tile is colored to closely match its surface. In the rare case of chipping, the exposed area blends better and is less noticeable. (see Cascade White).
How Flat is Your Tile
Since tiles cannot be made perfectly flat, all tiles have a slight amount of bending (warpage). This happens during the firing process. Tiles are produced at very high temperatures, and as they heat up and cool down, the material naturally expands and contracts. Even with the most advanced manufacturing, this movement cannot be completely eliminated.
ISO 10545-2 defines the allowable tolerances for flatness. This is one of the first things an installer or contractor will check, because flatness directly affects the quality of the installation. The flatter the tile, the easier it is to install with minimal lippage and consistent joints.
For this reason, you may want to ask for ISO 10545-2 compliance when purchasing tile, especially for large-format tiles where even slight warpage becomes more noticeable.
Are Porcelain Tiles Environment Friendly
Tiles manufactured in countries such as Italy, Spain, and Turkey are produced under these strict standards. If you are purchasing tile—especially white tiles, where certain pigments are more critical—you may want to verify that the release values meet the following limits:
Pb < 0.1
Cd < 0.01
Deep Abrasion : Mohs
Matte porcelain tiles typically score higher on the Mohs scale and are more resistant to visible scratching.
Polished porcelain tiles are less resistant to surface scratches—not because the tile is weak, but because the polished surface shows wear more easily.
Even so, polished porcelain tiles are still more scratch-resistant than marble, hardwood, or epoxy finishes.
If you are considering polished tiles for commercial use, keep in mind that practical scratch resistance is typically around Mohs 6. In such cases, you may also consider hard ceramic tiles (BIb: 0.5 < E ≤ 3%), depending on the application.
