- INTRODUCTION
- For over two decades, paper backed reinforcing wire was not recommended by the Ceramic Tile Institute.
- Because of the way the wire was made, the lapping of the wire was not being performed
properly when installed.
- The guage of the wire was not consistent and qualities varied.
- The tile installed over improperly lapped reinforcing wire within the mortar beds were cracking.
- The reasons for not promoting these reinforcing materials were printed in a CTI Field Report No. CTI 73-4-1.
- CTI Field Report No. CTI 83-12-1 primarily addresses the use
of the newly improved wires, which provide the needed one
full mesh wire to wire reinforcing lap.
- DISCUSSION
- The ceramic tire industry was plagued with failures to
their finished installations when paper backed wire
was used as the reinforcing material.
- When inspectors from the Technical and Job Problem
Committee investigated the reasons for the obvious
cracks through the tile and loose tile in predictable
patterns, the causes were the result of the paper
preventing a proper lap of the two pieces of wire.
- When the mortar bed cracks because of the improper lap, tile cracks.
- Contractors lodged complaints that paper removal was
too costly, but needed to properly lap the wire and
paper on the paper backed wire.
- To tear the perforated paper from the wire
sufficiently to get a full mesh lap of the wire is time consuming.
- The installing of paper and wire, each of which is a separate operation, became more
cost effective for the conscientious installer compared to the paper removal.
- K-Lath, a division of Tree Island Steel, Inc., heard about these problems, and came to
the Ceramic Tile Institute with a desire to have their materials tested; both
with the old design style and the new improved design.
- The purpose of the tests were to determine:
- First, if paper backed wire could be properly lapped to achieve sufficient reinforcing
within a mortar bed onto which ceramic tile would be bonded.
- Second, to determine the modulus of rupture (flexure) values of various reinforcing materials.
- Thirdly, to determine the correlation between support spacing of 12", 16" and 24".
- To achieve quality test data, stringent controls were set to remove any variables
that could effect the gathering of accurate results.
- The tests clearly point out that when paper backed wire reinforcing was improperly
lapped, the test samples broke prematurely.
- The position of the breaks within the samples positively correlates with the breaks we have
found in the field when the installers did not make proper laps.
- These cracks have caused an unknown cost in repairs to ceramic tile installers as well
as other finishers, including color coat plasterers.
- CONCLUSION
- The Ceramic Tile Institute does not recommend any reinforcing materials when they
are installed over studs that are greater than 16" on center.
- CTI recommends that if a mortar bed is to be machine applied as opposed to hand troweled,
it may be necessary to insist that the span be less than or equal to 12" on center
to achieve the desired deflection of less than 1,/360.
- CTI recommends that all reinforcing materials be properly lapped.
- The newly improved modified K-Lath is one of those recognized reinforcing materials,
that when properly lapped, will suffice to strengthen ceramic tile mortar beds.
- To verify that the correct material is chosen, look for the
Ceramic Tile Institute's Tested Material Logo on the packaging, cartons or material.
This logo is a mark of distinction for building inspectors and professionals to
recognize that the tile industry has tested and approved it's use.
- The reinforcing material and the tile installation must conform
with the Standards of the Tile Trade.
- Ceramic Tile Institute encourages other
manufacturers of reinforcing wires to submit their wire for consideration so that
they can also be listed.
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