Installation Guide

The term “mold” is used to describe visible fungal growth. Mildew is another common term which refers to the type of fungi found growing
on window sills and in bathrooms. Fungi are everywhere in our environment and are found both indoors and outdoors. However, the type and
amount found in the home can be an important health issue. Understanding how to effectively control mold growth is very important.
What is Mold?
Fungi are different from plants and animals. Fungi cannot produce their own nutrients as plants do and reproduce differently than both plants
and animals. Molds reproduce by making spores which travel through the air to deposit on surfaces. If the conditions are right for reproduction
they can grow and continue to multiply. The filamentous parts of mold attach to nutrients and form networks called mycelia. It is these networks
that are visible to us in the indoor environment. Molds come in a variety of colors, but we commonly see them as green or black.
Over 1000 different species of mold have been identified in homes, but they are not all toxic to humans. Molds growing inside a home
may release chemicals and spores and some may even produce mycotoxins. The chemicals released by fungi are called volatile organic
compounds (VOC). For example, ethanol is a common VOC that is responsible for the distinctive musty or earthy odor associated with mold.
Health Effects
Mold can cause damage to building materials and may have adverse health effects on some individuals. The susceptibility of people to develop
symptoms depends on the nature of the fungal material, genetic predisposition, age, state of health, and extent of exposure. Although there is
insufficient evidence in the scientific community to determine with certainty the association between mold exposure and the effect on human
health, it is of course recommended to control mold exposure in the home and workplace. Common health effects associated with exposure
to mold are a variety of upper and lower respiratory tract symptoms: cough; nose, throat and eye irritation; rhinitis; sneezing; and wheezing.
These symptoms are similar to allergies and associated with asthma. Mycotoxins are fungal metabolites that have a toxic effect on humans.
Toxic effects are associated with symptoms such as fever, nausea, headaches, and skin irritations.
Factors for Mold Growth
Fungi need a source of moisture, organic material to serve as a source of nutrients, and a warm environment with a temperature range from
50 to 107 °F (10 to 42 °C) to grow. For most species of fungi, a neutral to acidic pH is preferred, with a high pH level indicating an alkaline
environment that is generally not conducive to mold growth. Mold will reproduce in such conditions as long as moisture is present. Once the
area is dry, the mold may stop reproducing but can continue to be allergenic to susceptible people. If moisture is reintroduced, the mold will
again start the reproduction cycle and grow.
Controlling Mold Growth
As stated above, four conditions must be satisfied to support mold growth.
1. Mold spores
2. Food source (organic material)
3. Warm temperatures: 50 to 107 °F (10 to 42 °C)
4. Moisture
Mold spores travel through the air indoors and outdoors and are impossible to eliminate. The use of organic materials in construction is common
in today’s building environment. Examples include wood framing members (e.g., studs, joists, I-joists, and trusses), plywood or OSB subfloors,
paper-faced gypsum boards on walls and ceilings, etc. Room temperature falls within the temperature range suitable for mold growth. Therefore,
the control of moisture, including liquid water and water vapor, is the only viable method for controlling mold growth in the indoor environment.
Showers are critical areas with respect to mold and moisture control. They are commonly exposed to thousands of gallons of water per
year and high humidity levels. The tile covering alone will not prevent water and moisture penetration. As such, it is essential that an effective
moisture management system be designed and installed properly to protect surrounding building materials and prevent mold growth.
The traditional method for installing tiled shower assemblies creates a water in/ water out system. Since shower pan liners are placed below
the mortar setting bed in these assemblies, moisture is allowed to saturate the mortar bed before exiting the system through the weep holes
in the drain. When the pan liner is placed on a level substrate instead of a sloped surface, a relatively common error, moisture in the system
will have no means to exit through the weep holes in the drain and the mortar bed will remain saturated for extended periods of time. The
continued presence of moisture, combined with organic materials carried into the mortar bed by the rinse water, warm temperatures, and
reduced pH as soluble salts are washed out of the mortar bed, increases the risk of mold growth within the system.
The Schluter
®
-Shower System is an integrated family of products that creates a sealed system. KERDI is a bonded waterproof membrane
that is installed on top of the mortar bed and solid backing on walls. Tile is installed directly over the membrane using thin-set mortar. The
KERDI-DRAIN was designed specifically to ensure a simple and secure connection to bonded waterproof membranes, such as KERDI, at the
top of the assembly rather than below it. The resulting assembly does not permit moisture penetration into the solid backing or mortar bed,
thus limiting the amount of water behind the tile covering and allowing the shower to dry out between uses. Furthermore, KERDI is a vapor
retarder that protects wall cavities from water vapor penetration. Thus, the Schluter
®
-Shower System provides superior moisture management
and reduces the potential for mold growth within the system.
Regardless of the system used to waterproof a tiled shower, it is important to provide adequate ventilation (e.g., exhaust fans) in the bathroom
to effectively manage water vapor and reduce condensation on all bathroom surfaces.
Further discussion and recommendations for mold remediation can be found in various sources, including the following.
• “A Brief Guide to Mold, Moisture, and Your Home” – U.S. Environmental Protection Agency (EPA)
• “Mold Remediation in Schools and Commercial Buildings” – U.S. Environmental Protection Agency (EPA)
• “Mould Guidelines for the Canadian Construction Industry” – Canadian Construction Association
MOLD
The importance of mold control
46 MOLD — The importance of mold control