Failure Number 9 Showers-Improper
Design And/Or Installation
Successful showers include:
membrane assigned by contract from the builder or general contractor with the
waterproof membrane installed over a preslope of ¼ inch per foot toward drain
or outfall in order to protect all horizontal assemblies within the splash area
of the shower head. This includes shampoo
ledges, even if the shampoo ledge is above the 6-foot height requirement in the
shower. The waterproof membrane is required to be 3 layers of hot mopping or
equal as approved by the International Association of Plumbing & Mechanical
Shower receptors, curbs, pony
walls, seats, shelves, soap dishes, shampoo ledges, and windowsills are
horizontal assemblies. There should be no standing or ponding water in the
shower, when the shower is finished being used. All finished tile and stone
surfaces should have the same minimum ¼ inch per foot slope toward drain;
weep holes at shower drains.
Note there is not a requirement for
the wire horizontally to be mechanically fastened.
ANSI A108-99 accepts 2.5 pounds per
square yard expanded metal lath attached directly to studs.
assemblies with positive slope from all bathtub ledges, including the bathtub
rim, to drain water to the drain of the bathtub.
are properly supported.
with an integral 1-inch flange are required to make a watertight wall
intersection. For bathtubs without integral flanges, a tile bead kit is
installed. The tile bead kit must supply the equivalent of an integral 1-inch
flange surrounding the bathtub. The purpose of the 1-inch flange is to be able
to make a watertight intersection from the bathtub or shower pan with the wall
assembly. The Uniform Plumbing Code was changed in 1992 requiring all shower
receptors shall have a minimum 1-inch flange. Note the Tile Council of America
Handbook has an outdated bathtub configuration in the shower details in the
of a splashguard with curtain/drapery and rod installation.
door assembly is properly installed including using a mildew resistant silicone
sealant at frame intersections of the wall to the bathtub. Shower door enclosure, which does not allow
moisture to flow through the frame or splash underneath the shower door. Shower
door opening must be at least 22 inches.
pans properly supported and sloped ¼ inch per foot to drain with an integral
fixtures adequately sealed to the wall assembly with mildew resistant silicone
mixer valves and bathtub spouts.
floor covering that is not moisture sensitive.
- Adequate air ventilation to supply the minimum 5 air changes
per hour as required for ventilation.
a shower is changed to a steam room, then all wall, ceiling and floor
components of the shower are required to be equivalent to the steam room
details in the Handbook For Ceramic Tile Installation.
Requirements for cement
backer boards are covered in Failure Number 8 - Incorrect Backer Board
- Showers in public swimming pools are
required to be accessible.
Point to remember-The
cheaper the installation assembly the more perfect the installation has to be
installed in order to perform without failures. This theme leads me into water
resistant gypsum board installations in showers. The tile industry has deleted
water resistant gypsum board for direct bond of tile or stone in showers as a
suitable assembly. The Gypsum
Association was asked but would not change the Gypsum Association 216
publication to eliminate the requirement for the covering contractor to
waterproof the water resistant gypsum board. The primary problem with water
resistant gypsum board becomes an indoor air quality problem when the water
resistant gypsum board has been exposed to long-term moisture. BOG is
the term we use to identify bioorganic growth.
We used to say mold, mildew and fungus, but the mycologist and
toxicologist say we can’t say mold mildew or fungus unless we have a test run
to determine if the bioorganic growth is stachybatrys-charterum, penicillium or
aspergilli or some other microbial growth.
Water resistant gypsum board is not suitable for any
horizontal assembly in a shower unless covered and protected 100% by a
waterproof membrane. The exception to this may be ceiling assembly where the
maximum spacing of stud support is 12 inches apart.
Water resistant gypsum board cannot
be installed over any non-breathable backing surface. Water resistant gypsum
board will retain moisture and support bioorganic growth and loose structural
integrity at all locations where the water resistant gypsum board is installed
over a non-breathable backing surface. A
bathtub flange is a non-breathable backing surface. A waterproof membrane is a
non-breathable backing surface.
All details for water resistant
gypsum board require a minimum ¼ inch gap at the base of the water resistant
gypsum board above the flange of the bathtub, shower pan, or tile lined shower
receptor. Failure to supply the gap is a
defect and will contribute to failure of the water resistant gypsum board with
daily shower usage.
Therefore all mastic installations
in showers must achieve at minimum, 95% bond coverage and contact with the tile
and stone in the shower.
Remember our California VOC
requirements. Solvent-based mastic
cannot be used to install tile or stone in a shower in the State of California.
This only leaves multipurpose mastic and type II water-soluble mastic for
installation of tile and stone when mastic is specified by the builder to the
tile and stone contractor for usage in the shower. Gaps in the mastic with
multipurpose mastic and type II mastic will support bioorganic growth.
Failure to achieve the 95% coverage
and contact between the tile or stone and the mastic will further allow
condensation due to temperature changes, to collect in the void spaces between
mastic and the tile or stone.
In the early 1980’s, when type I
mastic was used in California, we
had mastic bleeding through stone installations in showers.
The International Building Code
still has water resistant gypsum board as a suitable substrate for direct bond
of tile in a shower assembly, but we hope this will be eliminated with a future
Setting materials used to installation stone in showers
should be either white thin-set or latex modified white thin-set, or epoxy.
A survey performed by the Tile Contractors
Association of San Diego was taken on the average lifetime expectancy of tile
installed over water resistant gypsum board in showers. The result is the expected lifetime usage of
the shower is 3 to 7 years.
Professional tile and stone
contractors in San Diego are asking
for a waiver of liability or issuing a disclaimer to the contractor when the
contract calls for installation of tile or stone directly bonded over water
resistant gypsum board.
A regular shower used 12 minutes a
day will use water equivalent to 8,760 inches of rain per year.
Using studs on a 24-inch center in
lieu of 16 inch maximum spacing in the walls is not a recognized backing for
tile and stone installations.