water beading up on black porcelain tile

Water Absorption Rate (Porcelain Tile)

Originally contributed by Jeff Butler • last updated 1/22/2021

Outside of picking tiles for their appearance, it’s important to pick tiles that are intended for the job. Some tiles are harder and more durable than others, with a wide range in between to meet any requirement. Others are more or less water resistant, a measurement determined by how much water a tile can hold before it cracks.


When talking about porcelain tiles, the water absorption rate refers to a rating system, developed by the The American National Standards Institute, that determines how much moisture a tile’s composition can absorb. To test the tile’s water absorption rate, it is boiled in water and weighed to measure the change from its original dry state. There are four different ratings for a tile’s moisture absorption rate: non-vitreous (7%), semi-vitreous (3-7%), vitreous (.5-3%), impervious (0-.5%). Water absorption rates help determine which tiles can be used for different applications.

Porcelain vs Ceramic

It’s important to consider where you’re putting up your tiles before you choose your tiles. Keep in mind things like the amount of traffic, the amount of water, and if they’re going to be inside or outside:

  • For exterior applications, select tiles with a very low water absorption rate (as close to an impervious rating as possible), especially in rainy and colder climates.
  • Tiles with a low water absorption rate also repel stains better, which makes them a good choice for areas like kitchens and bathrooms.