Failure Number 8 Incorrect
Backer Board Installations
Backer board installations not
taped and properly installed will cause indent fracturing of the stone directly
installed over the untapped joints between the backer board sheets.
Fastening of the backer board is
required to follow the manufacturers installation instructions explicitly.
Failures including indent
fracturing of tile, limestone, marble and granite installed over backer board
installations without tape are occurring. One contractor I talked with after he
removed and replaced, at his cost, an entire limestone floor over backer board installation,
admitted he was in a hurry and left the tape off. This was an expensive lesson
I testified in trial in Colorado
where the backer board was sold by a large home supply store to a builder. The
home supply store did not sell the tape, and did not offer the manufacturers
installation instructions. The builder
asked the limestone distributor if the limestone would crack. The limestone distributor said no. The builder installed the backer board, no
tape, and used liquid nails to adhere the backer board to the wood floor. The
limestone cracked and was fractured directly above each seam between each sheet
of the backer board. The judge ruled in favor of the limestone distributor and
the installer of the backer board failed to install the backer board correctly.
Backer board installation used in
showers is in lieu of a wire reinforced mortar bed. The installation still
requires a weather resistive barrier paper on all vertical wall assemblies and
waterproof membranes over all horizontal wood framing.
Installation of backer board in
showers directly to water resistant gypsum board is not an approved assembly
and will contribute to water damage of the water resistant gypsum board backing
in the shower assembly.
Some building jurisdictions have
eliminated water resistant gypsum board as a suitable backing for direct bond
of tile and stone in a shower assembly.
Sales representative of a major
cement backer board company, that also makes water resistant gypsum board, has
made claims representing the water resistant gypsum board division that are
erroneous. However, they are in two competing divisions of the same
company. The sales method is not right,
but the tile industry likes the end result to not bond directly to water
resistant gypsum board unless some form of waterproof membrane protects the
water resistant gypsum board. Type II mastic is not a waterproof membrane.
Recent investigations include
backer board installations on countertops.
The backer board is not adequately installed with the wrong side
up. One recent project, we went into the
kitchen and easily lifted the stone right off of the backer board.
The Ceramic Tile Institute of
Northern California is currently cautioning against veneer installations
utilizing backer board due to investigation of many veneer failures where
installations were promoted and specified by the backer board sales
Distributors selling the backer
board should sell the tape and give manufacturers installation requirements or
verify the contractor and employees have the manufacturers recommendations.
Contractors should inspect the
backer board before installation of stone over the backer board. If you are a
contractor installing backer board, follow manufacturers installation
directions explicitly. Remember the Marble Institute of America requires L/720
for suitable substrate to receive stone installation on horizontal surfaces.