How Water Absorption Affects Tile Suitability

28 November 2025

Why should you care about tile water absorption for exterior use, such as in areas near swimming pools and patios? And what about your interior spaces, such as bathrooms and laundries? In this article, you’ll learn how to select the right water absorption tiles (including low-absorption tiles) for the moisture-prone or external areas around your house.

What Is Tile Water Absorption — and Why Does It Matter?

Let’s start with the basics. The word “absorption” means the process by which one thing soaks up or absorbs another. And the term “tile water absorption” measures the amount of water a tile can absorb, expressed as a percentage of its dry weight. This is such an important topic for consumers that standards (AS ISO 13006 & AS ISO 10545.3:2020) have been issued to test and classify tiles based on their porosity and water absorption. These tile classifications are designed to help you make better-informed tile decisions, because high water absorption can lead to future problems such as moisture penetration and damage.

How Tile Porosity Is Measured

When tiles are produced, it typically involves grinding the raw materials into a powder and then firing the mixture in a kiln. With any powder, there are always minute spaces through which liquid or air can pass (porosity). However, differences in density and firing temperatures result in tiles with varying porosity.

How is porosity measured? In Australia, water absorption is determined using AS ISO 10545.3:2020, which outlines how to measure water absorption. The water absorption (%) is then calculated using the dry weight and soaked weight of the tiles.

The Link Between Absorption and Tile Classification

It’s pretty obvious that you wouldn’t use a high-absorption tile in a shower (which requires low-absorption tiles). So, how do you distinguish between them? Fortunately, there is a tile classification system based on whether the tile is vitreous (similar to glass in terms of water resistance) or non-vitreous (highly porous and prone to absorbing water).

• Less than 0.5% absorption: This is the most water-resistant category, highly vitrified porcelain, impervious, and suitable for outdoor and wet areas.
• 0.5% to 3% absorption: These tiles are suitable for wet areas.
• 3% to 6% absorption: This category includes ceramic tiles and can be used on floors and walls in domestic wet areas, however not recommended for outdoor areas.
• 6% to 10% absorption: Suitable for dry wall areas.
• Over 10% absorption: Not suited to areas with high moisture and typically used on walls only.

Where Water Absorption Becomes Critical: Wet, Outdoor & Exposed Zones

Here are some of the areas where your tile selection is critical:

Bathrooms and Showers

While your shower is an obvious example of needing low-water-absorption tiles, your bathroom area also requires low-absorption tiles due to splashes from basins, baths, and people stepping out of the shower.

Balconies, Terraces, and Roof Decks

Balconies, decks and terraces are prone to water ingress and high-absorption, porous tiles (which hold water) add to the weight of balconies and decks and can lead to rust problems with metal fixings such as balustrades.

External Walls and Facades

Similar to decks and balconies, tiles that hold excess moisture can cause structural damage and mould growth, especially in areas that are constantly exposed to the elements.

The Real-World Impact of High vs Low Absorption Tiles

What other problems are caused by high-water-absorption tiles? There are four main areas to consider:

Durability and Wear

Low-absorption tiles are made from a finer, denser mixture with less gaps (pores) and, in the case of porcelain, are fired at much higher temperatures than the more porous ceramic tiles. The extra density of the low-absorption porcelain tile, for example, gives it more strength, durability, and resistance to wear than ceramic (higher-absorption) tiles.

Frost Resistance and Expansion

Tiling in external areas is subject to frost in the colder months. When water freezes, it expands. Therefore, when porous tiles become frozen, the water trapped in the pores expands, and this pressure can crack, chip, or otherwise damage the tiling. That’s why high-density, low-porosity porcelain tiles are preferred over ceramic tiling for external use.

Choosing Low Absorption Tiles for Moisture-Prone Areas

How do you choose the right low-absorption tiles for your wet areas? What criteria should you use?

What Counts as “Low” Absorption?

According to the classification system, tiles with less than 0.5% water absorption have the lowest absorption (this includes porcelain tiles). Tiles with 0.5% to 3% absorption are also considered low-absorption. Tiles in the 3% to 6%, 6% to 10%, and above 10% ranges fall into the medium to high absorption categories.

How to Read Product Specs and Ratings

To access a tile’s specifications and ratings on our website, click on the picture of that tile (“View Product”). When the page for that tile appears, scroll down to “Technical Data Sheet” and click the “+” symbol on the right-hand side to expand it. Then click the download symbol, and the Technical Data Sheet will open. Scroll down to the “Physical Properties” section and find the “Water Absorption” line. If it is less than 0.5%, the tile is considered impervious and suitable for wet areas.

If there isn’t a Technical Data Sheet available on the product page, click on “Product Specifications”. These specifications will typically provide the slip ratings of the tile, as well as their “Composition” and see if it is Porcelain or ceramic. Porcelain is typically fine for any wet area. Ceramic tiles are generally not recommended for use in wet areas. For more information regarding the water absorption characteristics, our team is happy to help – call 1800 JOHNSON or contact us.

Matching Tiles with Adhesives and Substrates

If your tiles will be laid in a wet area, ensure that your substrate (such as cement sheeting) is dry, clean, and securely attached to the house framing. Select an adhesive that is compatible with the substrate, tile type and usage (wet or dry area).

Using Water Absorption Data to Justify Your Specification

If you are an architect, specifier, or homeowner, it’s always a good idea to research tile data and document your choices.

Risk Reduction for Projects

The Technical Data Sheet will always give the full water absorption information for that tile. Obviously, the lowest risk is to choose an Impervious tile (less than 0.5% absorption) and an appropriate adhesive for any wet areas.

Better Documentation and Product Traceability

You should download and save the Technical Data Sheet, the Catalogue/Brochure and Product Specifications for each tile you select from our product page. Keep similar records for any adhesive you choose.

Avoiding Disputes with Data-Backed Choices

By making your choices based on the technical data and specifications that we provide for each tile, you can easily justify your decisions to clients or concerned parties. For example, if you choose low-absorption tiles with high slip ratings, you can easily explain this and allay any concerns.

Explore Moisture-Ready Tiles for Bathrooms, Balconies & Beyond

When selecting the right tiles for your wet areas, you can easily find all the information you’ll need right here on our website. Explore our range of low-absorption, wet area tiles — perfect for bathrooms, balconies, and outdoor spaces.

This information is provided for general guidance only; always consult the relevant Australian Standards for specific requirements.