Your Total Guide to Underlayment for Tile Floors

Tile underlayment options are pretty abundant these days and can be used to address a variety of challenges or concerns. While in the past installers had to get creative when trying to level or reduce sound, today it's easy to accomplish.

Overview of Wall Flatness Required for Tile

ANSI specifications require that the floor surface is a certain degree of flatness based upon the length of the tile edges.
  • Tile edges less than 15" require less than 1/4" variation per 10' & less than 1/16" per 1'
  • Tile edges greater than 15" require no more than 1/8" variation per 10' & no more than 1/16" per 2'

Types of Underlayment for Tile

  • Backer board
  • Mortar beds
  • Patching compounds
  • Self-leveling underlayments (SLU)
  • Liquid and sheet membranes
  • Uncoupling membranes
When choosing what type of underlayment you're going to use under tile, you'll want to consider a few different factors. First, and most importantly, is the underlayment type flat enough? This is usually the main reason you even need an underlayment, so it should be the biggest consideration. Then you'll also want to consider if there are low spots to be addressed, if it also needs to be level, and if it needs to slope for drainage. Whether you choose backer board underlayments, floor underlayment preparation materials, or membranes - it's important to understand the appropriate option for the job at hand. We highly recommend reading the CTEF article, Ultimate Guide to Underlayment for Tile.

What is the best underlayment for tile?

Really, that depends on the job. There are four main factors to consider when choosing an underlayment which can help you decide, but sometimes it may take a combination to get the job done right. For example, a floor may need to be flattened with a trowel-application and then a crack suppression membrane may need to be used to improve the integrity of the floor beneath. As always, if you have questions about underlayment for your tile projects, stop by any of your local D&B Tile Distributors locations and our associates will be happy to help. We offer a full variety of options including sound control and more.