What Is Tile Underlay?

Written by tim anderson
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In the 21st century, a variety of materials are used in the construction of homes and offices, and in some cases there are areas which were not designed with ceramic tile or natural stone in mind. In these areas a tile underlay will provide the necessary structural integrity to support the installation for the duration of its lifetime.


At its very basic level, substrate is nothing more than any material existing beneath a given surface. In the case of ceramic tile and natural stone installations, it is the material beneath the tile installation itself which provides the structural integrity for the overall installation. It is required to be strong, yet at the same time flexible in order to swell and shrink with seasonal movement as well as to absorb various movements of the building over the course of time, such as sinking or buckling or even the simple wear and tear of foot traffic. The substrate is the single most important element of a ceramic tile installation.


Underlayment, otherwise known as tile underlay, is a product created specifically to take the place of the substrate if the existing substrate is unacceptable for use in a ceramic tile or natural stone installation. In certain cases the substrate materials may be either too weak or simply not suited for a tile installation, and in these instances an underlayment must be used in order to provide a barrier between the existing substrate and the tile installation. This provides the tile with an adequate foundation.


Fiberboard is a type of tile underlay formed out of compressed wood fibres, and can come in a variety of densities ranging from particle board to hardboard. Many people assume that plywood is a type of fibre board, but this is incorrect; plywood is nothing more than sheets of wood glued together, not fibres or particles. Hardboard is the most common type of fiberboard used for tile underlayment, with one of the more common brands being Masonite, designed by William H. Mason. It can be used in a wide variety of applications, and comes in a number of thicknesses depending upon whether or not it is a vertical installation or a horizontal installation.

Cement Board

Cement board is the most common type of tile underlay sold on the market on an international scale. It is nothing more than a combination of cement and glass fibres that are formed into sheets which are sold in various sizes and thicknesses. Cement boards not only act as a barrier between an inadequate substrate and the ceramic tile or natural stone installation, but also protect the ceramic tile installation from movement and impacts. More modern versions of cement board also include water-resistant gypsum board with special polymers inside to protect against mould and mildew.


It is considered standard procedure by tile professionals around the world to use a tile underlay in any case where there is not a concrete base for the ceramic tile or natural stone installation. They may be installed in interior or exterior applications and can be used for any project for the home or office. Whether you choose fiberboard or cement board is entirely up to you, as they both provide adequate structural integrity as a tile underlay.

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