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Application
in Wrong Location
The wrong application
is using a stone in a location not recommended or appropriate for
the stone.
All slates and
sandstones are not equal.
We caution against
installing slate and sandstone where there is constant wetting and
drying occurring. We are involved with a slate failure in Fresno
where the landscape water hits the slate and sandstone. In these
areas, you can literally peal the stone tile off in layers from
building. A swimming pool in Rancho Santa Fe has slate literally
shaling, spalling apart in pieces and falling into the swimming
pool.
Polished surfaces
do not belong installed on floors in wet areas due to slip, trip
and fall liability and reduced coefficient of friction. A honed
finish typically has better coefficient of friction than a polished
surface.
Mixing of stones
that cannot be polished in between polished stone creates a long-term
maintenance problem. Avoid the mixing of different stones with different
finishes together. Avoid using polished stone at building entry
pivot points where the stone could get wet. Prevent the slip trip
and fall liability by requesting the design be changed.
Type C and Type
D Marbles do not belong in areas subjected to moisture.
An area subject
to moisture includes showers, steam rooms, wet areas, saunas, entries
adjacent to exteriors of buildings, exterior of buildings, swimming
pools and spas, and direct bond to concrete slab on grade construction.
I will further explain moisture/vapor emission in concrete later.
Volcanic tuft
also called canterra and Adoquin stone have been oversold and these
stones do not perform well in swimming pool surrounds and in vehicular
traffic areas.
Flagstone does
not belong in vehicular traffic areas especially without adequate
expansion joints.
Builders in
California created a standard of care with the floor covering design
centers to use anti-fracture membranes to prevent minor shrinkage
cracks in concrete slabs from transferring through the finish floor
assembly.
Natural stones
should not be installed over moisture sensitive slip-sheet assemblies
used strictly for anti-fracture capabilities on concrete slabs subject
to moisture/vapor emission, migration, wicking, percolating and
transmitting through concrete slabs.
A proper application
would be to install an anti-fracture waterproof membrane to prevent
the moisture/vapor emission migration through the substrate from
affecting the natural stone floor or wall assembly. We recommend
using products like Composeal Gold, Noble-Seal TS, and Dal-Seal
TS, directly bonded to the concrete slab with a rapid setting mortar.
The rapid setting
mortar will heat hydrate and cure quickly.
When a membrane
is placed on concrete, the membrane will draw moisture to the underside
of the membrane.
Normal latex
will not cure when subjected to moisture for a long period of time.
The rapid setting
mortar has alumite, which is high pH friendly. A 9.3 pH alkalinity
can cause loss of bond to Portland cement setting materials but
not to rapid setting mortars in the high alkalinity condition.
This article
is part of a series of articles on Stone Failures (Dec. 2000) by
Greg Mowat
Forensic Tile
Consultants
9541 Vervain Street
San Diego, CA 92129-3523
(858) 484-8118, Fax 484-8302
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