- Introduction
Questions of concern are often raised when ceramic tile is to be installed
over a radiant heating system.
This concern usually is in regard to any
detrimental effect the heat from the radiant heating might have on the
bond of the tile.
- A Green Light
Happily, there is no problem with ceramic tile installed over radiant
heating systems because thse systems do not heat in extreme temperatures.
Maximum heats are somewhere in the 85 degree Fahrenheit range which does
not present any problem to a tile installation regardless of the method.
- Extreme Heats a Concern
Extreme heats are the enemy of many materials, and this is the reason
special refactory materials must be used when manufacturing ceramic tile.
It is also the reason why only fire brick will perform in the fire box
of a fireplace. Heat is also the enemy of many of our bonding materials,
and experience has taught us that organic adhesives will not perform
in hot areas such as restaurant walls behing grills or stoves and near
ovens. Epoxy mortars are not to be used where twmperatures are to exceed
140 degrees Fahrenheit. The best installation in such hot areas is the
conventional mortar method with wach tile backbuttered in addition to
the pure portland cement mortar trowled on the mortar bed. This article,
however is on radiant heating, so let's discuss the methods of tiling
over radiant heating.
- Methods
A. Although attempts have been made to develop flat, low voltage electric
mats for radiant heating, most systems employ hot water running through
pipes. These piped hot water systems vary in the way they are designed.
B. Thin-set Method with Membrane.
When the radiant heating pipes are buried in the concrete, a thin-set
system can be used if a thin bondable membrane is installed over the
concrete first. When the radiant heating pipes are buried in the concrete,
the concrete is often cracked right over the pipe as the pipe acts like
a weakened plane joint. If the tile is bonded to the concrete with the
buried pipes, and the concrete cracks, it will also crack the tile. The
thin bondable membrane will prevent the cracks in the concrete from cracking
the tile. There are several manufacturers making the thin bondable membranes
which can also serve as waterproof membranes. After a membrane manufacturer
has been selected, that manufacturer's complete system, including the
bonding of the tile to the membrane, should be followed.
C. Conventional Mortar Method
Where the pipes are buried in the concrete slab, the tile can also be
installed in the conventional mortar method. When the conventional mortar
method is used, it is best to use a cleabage membrane over the slab containing
the radiant heating pipes. The tile is then installed in a wire reinforced
mortar bed overt the cleabage membrance.
D. Pipes on Top of Concrete
When the pipes for the radiant heating system are laid on top of the
concrete slab, a somewhat worrisome system exists. If the mortar bed
is placed directly over the pipes, the pipes have a tendency to make
weakened plane joints in the mortar bed and crack through the mortar
and tile directly over each pipe. It is recommended, therefore, to first
use a fill of mortar between and up flush with the top of the pipes,
let that mortar bed cure for at least 24 hours, then place a cleavage
membrane over the fill an install the tile on a wire reinforced mortar
bed over the cleavage membrane.
- Conclusion.
Because of the various methods that can be used, early planning is important.
The early planning is to have the structure built to allow for the mortar
thickness and for the weight of the mortar, plus the weight of the tile.
Mortar weights twelve pounds per square foot, on inch thick. Ceramic
tile weighs five to six pounds per square foot, on-half inch thick.
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