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How do I tile over an exterior deck or balcony?
We are often asked about tiling exterior decks. The
TCA Handbook contains two details for decks, F103 (Roof
decks) and F104 (Balcony decks). Additionally, many
manufacturers of setting materials also make roof deck
drainage systems. Often, these proprietary systems are
highly modified versions of the F103 system, allowing
precipitation to drain away from the tile.
There are no backerboard systems in the handbook for
exterior decks - however, under some circumstances and
with appropriate waterproofing, backerboard manufacturers
may authorize such an installation. For details, you
will need to speak with manufacturers directly as such
methods tend to be highly product specific.
Many issues must be considered when tiling exterior
environments:
1) The tiles must be rated by the manufacturer for
exterior use. In addition to certain industry tests,
such as freeze-thaw, crazing, and water absorption,
the manufacturer also considers other properties of
the clay body and how the tile was fired. Additionally,
some manufacturers have proprietary testing protocols
and field testing they use to further assess the suitability
of tile for exteriors.
2) Satisfactory exterior installations must be able
to drain water from the system before it gets a chance
to absorb into either the tile or the layers below the
tile. Since most tiles are water impermeable, the only
water that can get into the system goes through the
grout joints or though the substrate itself. The installation
and the proper slope to drain will determine the extent
to which the system saturates itself and in turn its
ability to remain intact over time in freeze/thaw or
high temperature environments.
3) The setting materials and substrate must also be
appropriate for the exterior conditions present. Freeze/thaw
resistant mortars and non-redispersible polymers are
often necessary. Expansion joints must also be designed
into the system to allow for the movement typical with
large temperature variations and exposure to water.
4) The system must be able to accommodate wind and
snow loading and other building movement. Commonly,
exterior forces acting on the tile layer can be much
greater than a comparable interior job. Accordingly,
the installation must be suitably rigorous - methods
developed for interior installations are not necessarily
appropriate for exterior installations.
Remember that exterior tile systems over inhabited
space need a waterproof substrate below the tile. Without
such, water will be able to penetrate below the tile
layer and could cause damage. Even when tiling over
areas not over inhabited space, serious consideration
must be given to controlling where the water will go
and how it will affect the tile and substrate.
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