Rectified or non-rectified porcelain: what really changes on site

Rectified is one of the most common words on a porcelain price list and one of the worst explained. It is neither a finish nor a grade: it is a mechanical process after firing that changes how the tile is laid, what it costs to lay and how the finished floor looks. These are the differences that matter when there is a job on the line.

What exactly is a rectified porcelain tile

All ceramic tiles shrink during firing, and that shrinkage is never perfectly uniform: two tiles from the same series can differ by a millimetre or so and their edges are not perfectly straight. Rectifying means cutting the four sides of the fired tile with diamond discs to leave the edges square and every tile in a batch at exactly the same size. The result is a sharp, straight edge and minimal dimensional tolerance.

A non-rectified tile keeps the edge as it comes out of the kiln: slightly rounded and with small size variations between tiles that the joint absorbs.

The joint: 1.5-2 mm versus 3-5 mm

This is the visible difference. Rectified tiles allow 1.5 to 2 mm joints, almost invisible when the grout matches the tile, giving the seamless look sought in large format and in marble or cement effects. Non-rectified tiles need at least 3 mm, and 4 or 5 in large sizes, to absorb the size differences and the rounded edge. Neither is better or worse: in a terracotta effect or a rustic look the wide joint is part of the design.

Installation and labour

With a minimal joint every defect shows: a one-millimetre lip between two rectified tiles is both visible and felt underfoot. That is why rectified tiles demand a perfectly level substrate, double-buttering, a levelling system with wedges and an installer used to large format. That care costs time: labour per m² is somewhat higher than with non-rectified material, where the joint forgives small irregularities in the substrate and the laying.

On the other hand, rectified tiles make junctions easier: the straight edge allows clean mitres at corners, steps and trims without profiles, and on walls it avoids the staircase effect that rounded edges produce under raking light.

Cost and availability

Rectifying adds an industrial process, so the tile is somewhat more expensive than its non-rectified equivalent, and that premium adds to the labour cost. In return, almost all mid-range and high-end porcelain made in Castellón today is rectified, especially from 60x60 upwards, and in large format the non-rectified option simply does not exist. Our series are rectified except for small-format ranges with a handmade look, such as Cotto 33.3x33.3.

When to choose each

• Rectified: large format, marble, cement and stone effects, continuous floor and wall, mid-range and high-end housing, hotels and retail.
• Non-rectified: small formats, rustic or handmade looks, jobs where the substrate is not level and will not be screeded, and budgets where labour is the limiting factor.

A note for distributors

When comparing price per m² between suppliers, check that both are talking about rectified or both about non-rectified: the difference in industrial cost is real and a cheaper offer may simply be leaving the process out. Our trade price list states rectified series by series, and product pages show it as a badge. To understand the rest of the terms on a tile price list, the complete porcelain stoneware guide goes through them one by one.