Nominal Sizes
The standard or stated dimensions of a tile, that are often different from its exact physical measurements, are nominal sizes. A nominal size is a rounded number size that is used in selection, labelling, and design planning. In most cases, the actual dimensions of a tile vary from their nominal size due to realities of production, including firing shrinkage.
Nominal Size vs Actual Dimensions
To understand the tile nominal size, it is necessary to know the difference between measured size and labeled size. While nominal size is often used to keep the communication simple, the actual size is necessary to understand the dimensions of the finished product after processing and firing. The major differences between these two are as follows:
| Aspect | Nominal Size | Actual Dimensions |
|---|---|---|
| Meaning | Stated or labeled size | Measured physical size |
| Purpose | Used for naming and selection | Used for installation accuracy |
| Precision | Rounded and standardized | Falls within tolerance range |
| Example | 24×24 inches | Slightly smaller than stated size |
This difference is majorly seen because tiles are produced with a specific manufacturing size tolerance, making slight variations necessary to ensure proper installation and better grout spacing.
Size Variations: Reasons
Most commonly used tiles such as porcelain and ceramic are manufactured under high temperatures where they may have to go numerous cycles of firing and cooling. Temperature affects the size of the materials used to manufacture the tiles in the form of expansion and contraction. As these processes are natural, it is physically impossible or unfeasible to achieve perfectly identical sizes.
To mitigate major size issues, tiles are manufactured by following a size tolerance range which limits the variation. While manufacturers try to maintain high dimensional accuracy, minor tile size variations are natural, even in the most premium tiles. Understanding this helps set realistic expectations and supports better planning during installation.
Size Grouping and Rectified Edges
To avoid major issues due to variations, tiles are sorted using a method called caliber sizing or calibration grouping after the final stage of production. This is done using the tiles’ actual finial measurements. Through this, it can be ensured that tiles with the same actual dimensions end up together.
Mixing tiles from different calibration groups can lead to uneven joints and misaligned installation, especially in the case of large-format tiles.
In some cases, tiles are processed further to improve size precision. This process is known as creating rectified edges in which tiles are mechanically cut after firing to create more uniform and perfect edges.
This enhances overall dimensional accuracy and allows for tighter grout joint spacing, creating a cleaner and more seamless look. While rectified tiles reduce the visual impact of manufacturing variance, they still operate within a defined tolerance range.
Ultimately, while nominal sizes provide a convenient and standardized way to describe tiles they are not the exact measurements. It is recommended to know both actual dimensions and the nominal sizes before beginning an installation.