Instructions / Assembly

INSTALLING TILE
ON WALLS
Setting tile on vertical surfaces and ceilings brings extra challenges like deflection and gravity to the project. Here are some of
the most commonly asked questions about how to successfully install tile on walls, indoors and out.
WHAT CAN BE INSTALLED AND WHERE
Question: What is the maximum tile size and weight that can be installed on
walls?
Answer: For direct bond installation on commercial projects, International
Building Code limits tile on exterior walls to less than 24" on one
side, less than 3 square feet total area and less than 9 lbs. per
square foot. There are no restrictions for interior walls, but some
suggest that maximum weight should not exceed 15 lbs. per square
foot. Larger and heavier tiles will require anchoring with mechanical
fasteners. Be sure to consult your local building code or other
authorities having jurisdiction for tile size and weight limits on your
specific project.
Question: Is gypsum drywall a suitable substrate for tile installation?
Answer: International Building Code restricts the use of gypsum drywall, including water-resistant gypsum drywall, in wet
areas such as showers and tub surrounds. In these applications, the gypsum drywall should be removed and
replaced with a cement backerboard such WonderBoard
®
Lite. Bare gypsum drywall is a suitable substrate in all
dry, interior applications.
Question: Can tile be directly installed to wood surfaces or foam insulation?
Answer: No. Plywood and OSB are not suitable surfaces for installing tile on walls and foam does not have the tensile
strength to support tile. WonderBoard Lite cement backerboard or lath and a cement scratch coat must be
installed to the wood or foam surface before the installation of tile with an appropriate mortar.
Question: Can tile be installed on painted surfaces?
Answer: The bond of the tile to the surface will only be as good as the bond of the paint to that surface. In most cases, the
paint should be removed. If the paint is well bonded, the painted surface can be well cleaned and roughened with
sand paper. The prepared surface can then be primed with MBP Multi-Surface Bonding Primer and tiles installed
with a suitable polymer-modified thin-set mortar.
Question: Is there a flatness guideline to follow when tiling walls?
Answer: To ensure a flat tiled surface, it is important to start with a flat substrate. The wall surface should be installed or
corrected so that there are no deviations greater than ¼" in 10 feet. For shower walls and tub surrounds, install
WonderBoard Lite 1/4" backerboard. If tiling on existing walls, apply and smooth General Patch to bring the
surface into flatness compliance prior to tiling. Be sure to remove any bond breakers like dust or residues before
applying membranes or mortar to any surface.
Question: What is the requirement for movement joints when tile is installed on walls?
Answer: For exterior applications, the requirements are the same for walls and floors. Install flexible movement joints every
8-12 feet and at all changes of plane. The minimum movement joint width is the same as the grout joint and not
less than ¼". Larger joints provide better protection to large format tile, with any side longer than 15". For interior
applications, the movement joints should be placed every 20-25 feet, unless the tile assembly exposed to direct
sunlight and then they should be spaced every 8-12 feet. Always consult with the Project Architect on commercial
projects.
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