How to Read a Tile Data Sheet: Water Absorption, PEI and Rectified Edges

Reading a tile data sheet is the difference between choosing by the photo and choosing with real judgement. Behind every collection there is a spec sheet —ISO 10545 and EN 14411 standards— that states, without poetry, how that tile will behave underfoot, in your kitchen, or on a frost-exposed terrace. Water absorption, PEI, rectified edges, slip resistance and shade variation are the parameters that truly matter. In this guide we explain what each one means and what value to look for by use, so the data sheet stops being a riddle and becomes your best ally.

What is a tile data sheet and why should you read it?

The data sheet is the document that summarises a ceramic tile’s measured performance according to standardised tests. In Europe, the reference framework is the EN 14411 standard (classification of ceramic tiles) and the ISO 10545 series of tests, which defines how each property is measured. It is not marketing: these are lab values obtained with methods comparable across manufacturers. Why does it matter? Because a beautiful tile can be the wrong choice. A porcelain designed for walls won’t withstand hallway traffic; a delicate glaze scratches in a busy kitchen; a tile not rated for outdoors cracks with the first frost. The data sheet anticipates all of this. Learning to read it saves surprises and lets you compare collections from different brands —Ragno, Emil Ceramica, Coem— on equal terms. Throughout this guide we use one simple principle: each parameter answers a question about use. Floor or wall? Indoors or outdoors? Wet area? Heavy traffic? With those answers, the sheet almost reads itself.

Water absorption: the figure that defines the ceramic body

Water absorption is probably the single most important parameter on the sheet. It measures the percentage of water the ceramic body can absorb, determined per ISO 10545-3. The lower the absorption, the more compact and less porous the material, and the better it resists frost, staining and stress. EN 14411 classifies dry-pressed tiles (Group B, the usual method for porcelain and most ceramics) by absorption:

• Group BIa — absorption ≤ 0.5 %: true porcelain stoneware. A practically impervious body, suitable for floor, wall, indoors, outdoors and demanding traffic. The benchmark for top technical quality.
• Group BIb — 0.5 % < absorption ≤ 3 %: fine stoneware, very durable, right for most residential uses.
• Group BIIa — 3 % < absorption ≤ 6 %: medium-porosity stoneware. Fine for many indoor floors, but check frost and stain suitability.
• Groups BIIb and BIII — absorption > 6 %: porous bodies. BIII (> 10 %) is the typical light glazed wall tile, meant for indoor cladding, not flooring.

The rule of thumb: for floors, outdoors or wet areas, look for BIa (≤ 0.5 %). For indoor wall cladding, a more porous, lighter body is perfectly valid. Our entire porcelain flooring range starts from this low-absorption logic.

PEI: the glaze’s abrasion resistance

If absorption defines the body, PEI defines the surface. It is an index of the glaze’s surface abrasion resistance on glazed tiles, measured per ISO 10545-7. In other words: how much the visible layer withstands before footfall, grit and use begin to wear its shine or pattern. It is expressed in classes from PEI I to PEI V (the standard numbers them 0 to 5). Broadly:

• PEI I: minimal abrasion. Walls or areas without footwear traffic only.
• PEI II: light traffic, no grit. Bathrooms and bedrooms with gentle use.
• PEI III: medium residential traffic. Most home floors: living room, kitchen, hallways.
• PEI IV: heavy traffic. Home entrances, terraces and light commercial spaces.
• PEI V: very intense traffic. Demanding public and commercial use.

Two important caveats. First: PEI only applies to glazed tiles. A full-body technical porcelain (colour through the whole thickness) has no PEI, because it doesn’t rely on a surface glaze; its resistance comes from the body itself. Second: a high PEI doesn’t mean “better”, it means “more wear-resistant”. For a wall, PEI I is the correct —and usually cheaper— choice.

Rectified vs. non-rectified: edges, joints and aesthetics

Rectified describes the tile’s edge finish. A rectified tile has been mechanically ground on all four edges after firing, so every piece is exactly the same size and the edge is squared to 90°. Dimensional variation between rectified pieces is very small, typically ≤ 0.5 mm. What does this mean in practice? That you can lay with a minimal joint, around 2 mm, achieving that almost seamless, clean, contemporary surface minimalist projects seek. The sharp edge and high precision allow extremely fine, perfectly aligned grout lines. A non-rectified tile (pressed, with a natural moulded edge) goes straight from kiln to packaging. Its edge is slightly rounded and its dimensional variation greater, so it needs a wider joint —no less than 3 mm— to absorb that tolerance. It isn’t worse: the more generous joint forgives small substrate irregularities and brings a warmer, more rustic character. Don’t confuse rectified with calibre. Calibre is the actual size group a batch of non-rectified tiles belongs to; when buying, every box should be the same calibre and same shade so they match. With rectified pieces calibre all but disappears as an issue, because the size is uniform.

Slip, flexural strength, frost and shade: the rest of the sheet

The data sheet doesn’t end there. These parameters complete the reading and often decide a tile’s real suitability. Slip resistance. Crucial for floors, bathrooms, kitchens, terraces and pools. It’s expressed with several systems —class R9–R13 (ramp test, German DIN 51130), A/B/C groups for barefoot areas, or the PTV/pendulum value. The higher the R number, the more grip. Given its importance we cover it in a dedicated slip-resistance guide, worth reading before choosing flooring for a wet or outdoor area. Flexural strength and breaking load. Measured per ISO 10545-4, it indicates how much force a tile withstands before breaking. Porcelain (low absorption) offers high values, enabling large formats and slim thicknesses. Relevant if you want XXL pieces or raised-floor paving. Frost resistance. Per ISO 10545-12, expressed as “resistant/not resistant” to freeze-thaw cycles. It goes hand in hand with low absorption: a BIa body barely retains water, so it doesn’t crack when it freezes. Essential for any outdoor use, including Mallorcan terraces with cold nights. Stain resistance. Per ISO 10545-14, it rates cleanability from class 1 to 5 against staining agents (class 5 is the highest). It matters in kitchens, worktops and high-use areas. Shade variation (V1–V4). Not a defect but an aesthetic decision by the manufacturer, indicating how much colour and pattern differ between pieces:

• V1 — uniform appearance: minimal variation, homogeneous and serene.
• V2 — slight variation: subtle nuances between pieces.
• V3 — moderate variation: noticeable shifts in tone and graphics, typical of wood and stone looks.
• V4 — high variation: each piece markedly different; strong artisanal or natural character.

Knowing the V index avoids surprises: for visual calm, prioritise V1–V2; for living naturalness, V3–V4 is your ground.

Summary table: sheet parameter → what it means → what to look for

Conclusion

A tile data sheet is not fine print: it’s the map that guarantees the tile you fall for is also the right tile for your space. With three basic readings —absorption (BIa for floors and outdoors?), PEI (does it withstand the expected traffic?) and rectified edges (minimal joint or natural edge?)— you already avoid the most common mistakes. Add slip resistance in wet areas, frost resistance outdoors and the V shade index for aesthetics, and your choice will rest on data, not intuition. At Gomila Cerámica we work with brands —Ragno, Emil Ceramica and Coem— whose data sheets live up to their design. If you’re unsure about a specific spec sheet, write to us: reading a data sheet with you is part of what we do.

Frequently asked questions

• What does BIa mean on a tile data sheet? BIa is the EN 14411 group for dry-pressed tiles with water absorption ≤ 0.5 %. It’s the most compact porcelain: suitable for floor, wall, indoors and outdoors, and resistant to frost and staining.
• Which PEI do I need for my home floor? For most residential floors (living room, kitchen, hallways) PEI III is enough. For higher-traffic home entrances or terraces, choose PEI IV. PEI only applies to glazed tiles.
• What’s the difference between rectified and non-rectified tile? Rectified tile has all four edges ground to 90° and a uniform size, allowing a minimal joint of about 2 mm and a seamless finish. Non-rectified keeps the moulded edge and needs a wider joint (≥ 3 mm).
• What is shade variation V1, V2, V3 and V4? It indicates how much colour and pattern differ between pieces of the same model. V1 is virtually uniform and V4 shows large piece-to-piece variation for a natural or artisanal effect.
• How do I know if a tile is suitable for outdoors? Check the sheet for frost resistance (ISO 10545-12), low absorption (ideally BIa ≤ 0.5 %) and slip resistance suited to outdoor use, usually R11 or higher.