What are Rectified Tiles & Why is it Important?

Rectified tile are tiles that have been mechanically processed to ensure that all the tiles are uniform in size and are perfectly square.  If you've ever baked bread, you know that it's impossible to predict the exact eventual size of the product: it expands. While ceramic and porcelain clays do have more predictability than dough, they still are subject to size variability based on tiny differences in firing temperatures and composition of materials: tile shrinks upon firing. So, ordinary tiles that are molded and then fired, but not rectified, will have slight dimensional differences that may affect how neatly and precisely the tiles are laid out.
Note that rectifying affects only the tile's edge dimensions not the thickness of the tile.

If you want thin grout lines of 3mm or less
The main reason for rectified tiles is to allow for minimal grout joints. look at the picture above, a floor like this would be impossible with unrectified tiles.
The thicker the grout line, the more tolerance you have available to accommodate oddly sized tiles. You'll notice that quarry tiles, those thick, often red, and often unrectified tiles you see outdoors, may have lines as thick as a centimetre or more to cover for imperfect dimensions.

If you are laying 45cm or larger tiles
It's rare to find small rectified tile. Mostly 30x30cm tiles would be the smallest rectified tile. Mosaics are also often cut and rectified.
If you're laying polished porcelain tile, you'll almost certainly be setting thin grout widths.

Lippage
Though this is not a grout-line issue, you need to make certain that your substrate is absolutely flat when laying large tile. Lippage will be immediately apparent when laying tile with thin grout lines.

Rectified applies only to fired tile. You won't find rectified marble, granite, or travertine. Since these are natural stones, they are by definition rectified since they need to be cut from larger blocks of stone.
Since rectification is an additional process, rectified tiles are often slightly more expensive.
Below a rotary blade slivers off a few millimetres from each edge, a noisy process. To prevent dust, water is used.

We are currently planning a KREM Technical catalogue specifically aimed at architects. All tiles in these ranges will be rectified. Any suggestions for product or technical content to be included are welcome. Contact us here.

All the best,
The Link International team, KREM tiles.