Failure Number 11 Attachment
of Wire To Wood Floor Assembly
There is no requirement in ANSI
A108 or in Assembly Method F141 in the Handbook For Ceramic Tile Installation
to mechanically fasten the 2-inch by 2-inch 16/16 gage reinforcing wire fabric,
or equal, to the wood floor assembly.
Mechanically fastening the wire
transfers the stress that occurs with moisture and thermal expansion and point
load stresses occurring with weight transfer from the top of the tile or stone
Indent fracturing of the tile and
stone floors are the first indication the wire was improperly attached to the
wood framed floor assembly.
The failure is prominent in radiant
heat floor systems when the wire is attached to the wood floor assembly. The correct method is to install the radiant
heat tubing, fill the spaces between the tubes in with mortar, install a cleavage
membrane, and install a wire reinforced mortar bed, and stone or tile. We had
one home in Rancho Santa Fe where the marble contractor installed stucco mesh
underneath the radiant heat tubing and mechanically fastened the stucco mesh
into the wood floor. The red travertine stone from Spain
was installed. I was called in when the
red travertine stone from Spain
started indent fracturing. The fracturing was occurring in 3-foot grids
initially. A lawsuit was filed. The
Builder blamed the lack of wood floor assembly for excessive deflection.
Destructive testing proved the wire
was in the wrong location and was fastened improperly to the wood floor. By the
time the lawsuit was settled, the indent fracturing was occurring as close as 8
inches apart. The radiant heat tubing
creates a weakened plane joint causing cracking of the mortar and resultant
indent cracking and fracturing of the stone. The floor was replaced at a cost
exceeding $250,000. An expensive lesson
to learn not to mechanically fasten the wire to the mortar bed and not to
listen to the radiant heating engineer who said to place the wire underneath
the tubing, instead of using a cleavage membrane and place the wire in the
mortar bed above the radiant heat tubing.
Since this time, the Marble
Institute of America has published the requirements for the wood floor assembly
to achieve L/720 instead of L/360 as published in Assembly Method F141 in the
Handbook For Ceramic Tile Installation.
We are in complete disagreement
with assembly method F145 introduced in 1997 into the Handbook For Ceramic Tile
Installation. We have investigated failures upon failures of wood floor
assemblies where wire, expanded metal lath, and stucco mesh are mechanically
fastened to the wood floor assembly. Bob
Stanaland, CTA with the Ceramic Tile Institute of Northern California has been
investigating similar failures for years.
I have had correspondence with Robert Daniels of the Tile Council of
America, Inc. and with Gray LaFortune, CTC with the Ceramic Tile Institute of America,
Robert Daniels response was the
assembly is only for less than 100 square feet and contractors in the northeast
portion of the United States
claim they have been installing this method successfully for years. I question
if the contractors have had the opportunity to go back and look to see if the
installations are performing or failing.
When I served as a representative
to the Tile Council of America Bi-Annual Handbook For Ceramic Tile Installation
Conference, I documented the bonding to wood failures investigated by myself,
while investigating at the Ceramic Tile And Marble Institute of San Diego, the
Ceramic Tile Institute, and the Ceramic Tile Institute of America. The purpose was to oppose Bob Moore proposing
modified epoxy emulsion mortars as suitable for bonding to all wood assemblies.
I have lawsuits today with failures of stone installed on floors and decks due
to the mechanical fastening of the wire reinforcing to the wood framing. The installing contractors who mechanically
fastened the wire to the wood floor are now claiming the sole fault is the wood
floor was not built to L/720 as now required by the Marble Institute of
I had discussions during attendance
at a Ceramic Tile Distributors of America Convention in Texas
with a concrete tile manufacturer sales representative. He stated their product
is installed successfully with direct bond to plywood floors. I related I was traveling to Boston
to attend the American Society of Association Executives Annual
Convention. He related the bar in the
hotel I was staying at had this installation.
In Boston, I visited the bar
with concrete tile directly bonded to the wood floor. The entire floor was failing with fractured
tiles and grout. I followed up with a courtesy letter to the sales
representative advising him of the failure observed.