Section 6: Types of Membranes

6.1 Overview

There are various membrane types that can be specified within a ceramic tile/stone installation system, depending upon the requirements of the installation. The membrane types include;

Waterproofing

Crack isolation/Anti-Fracture

Sound Control

Combination of Two or More Element Types

Adhesive Types That Incorporate Two or More Element Types

Waterproofing protection is one of the most practical steps to ensure the longevity of most mass transit tile and stone installations. It not only protects the spaces below and adjacent to the tile/stone installation, it also protects the setting bed, reinforcing wire (if used), concrete base and concrete reinforcing from potential damage and corrosion. Since damage to many flooring components can occur, it is no surprise that the majority of construction liability claims involve water damage that has resulted from the lack of, or an improperly installed, waterproofing membrane. Today’s pressures of completing projects quickly often leads to tile and stone installations being rushed and installed improperly. The advanced technology that goes into waterproofing, crack isolation and sound control membranes allows the end user to take advantage of quicker curing times, which allows faster time to flood testing and ultimately allows the tile or stone installation to move forward in a more timely manner. The various membrane types of waterproofing, anti-fracture and sound control membranes include; peel and stick, trowel applied, liquid applied, and sheet good types.

The traditional asphaltic/bitumen based roofing type waterproofing membranes are omitted from this manual. However, it is important to note that if they were to be specified and used in a commercial flooring application, a full, wire-reinforced non-bonded thick bed mortar bed would be required. Direct bonding to these membrane types is not possible.

The most important factor in all types of membranes is to closely follow the membrane manufacturer’s installation recommendations. This will significantly reduce the possibility of job site problems and potential failures. Adhering to industry standards is also paramount to the success of the tile and stone installation. Consideration should be given to membranes that carry plumbing and building code approval as well as being environmentally friendly (e.g. LATICRETE® 9235 Waterproofing Membrane, LATICRETE Hydro Ban, LATICRETE Blue 92 Anti-Fracture Membrane, LATICRETE 125 Sound and Crack Adhesive, LATICRETE 170 Sound and Crack Isolation Mat).

Many crack isolation, sound control and waterproofing membranes can be applied over concrete, mortar beds, exterior glue plywood ,and cement backer board. Some waterproofing membranes serve as both waterproofing and anti-fracture membranes in one (e.g. LATICRETE 9235 Waterproofing Membrane or LATICRETE Hydro Ban).

The installation of waterproofing is covered under ANSI A108.13 “Installation of Load Bearing, Bonded Waterproofing Membranes for Thin-set Ceramic Tile and Stone”. Crack isolation membranes and adhesives are covered under ANSI A108.17 “Installation of Crack Isolation Membranes”. The product standards for waterproofing can be found under ANSI A118.10 and the product standards for crack isolation membranes can be found under ANSI A118.12. Selection of membranes must take into account the conditions of a mass transit application including heavy traffic (pedestrian and/or vehicular), harsh cleaners, and, in many mass transit applications, excessive vibration.

6.2 Sheet Membranes

Sheet membranes are typically made from chlorinated polyethylene, polyvinyl chloride, and other materials. These membranes are made in a variety of lengths and widths to accommodate many different types of installations with product performance that can vary depending on the manufacturer and product. Generally, these sheet membranes have a polyester or fiberglass scrim or netting bonded to both sides which allow it to be bonded to the substrate, and the tile or pavers to bond directly to the sheet membrane.

Typically, a latex portland cement mortar (meeting ANSI A118.4) is used to bond the membrane to the substrate and to bond tile/stone to the membrane. If time is a limiting factor, some membrane manufacturers allow the use of a rapid setting adhesive to bond the membrane to the substrate, which in turn allows the installation of tile or stone to take place quickly, without the loss of bond of the membrane to the substrate.

It is very important to consider the moisture vapor emission rate (MVER) and the alkalinity of the concrete slab prior to the installation of these products. A concrete slab or cement mortar bed with a high MVER rate and/or high alkalinity can create adhesion problems, and can possibly be destructive to the membrane and the overall installation. The sheet membrane manufacturer can provide information on the MVER and alkalinity limits of their products.

Sheet type membranes are pressed into contact with the substrate in an effort to eliminate air bubbles and voids under the membrane. Generally this can be done using a 75- or 100 (34–45kg) pound sheet vinyl roller. It is important to note that the substrate or setting bed surface must meet the same substrate smoothness criteria required for direct bond tile or stone applications. If the surface is not smooth and flat enough for tile or stone, then it is not smooth and flat enough for a membrane.

Precautions and concerns with sheet type membranes are as follows:

1. Trapping air below the membrane can cause air pockets to form and radically diminish the compressive strength of the overall tile system.

2. Overlapping and sealing the seams. The seams may require treatment with a suitable sealant or solvent. This process can be very involved and requires careful attention to detail.

3. Membrane thickness increases in the folds of inside and outside corners, seams and other transition areas. Additional flashing or skim coating treatment may be necessary to minimize the effects that this can have on the finish tile appearance.

4. High alkalinity can attack and adversely affect some sheet type membranes and the adhesive used to bond the membrane to the substrate.

5. High MVER – generally in excess of 5 lbs/1,000 ft2/24 hours (283 mg/s m2) can have a negative impact on the adhesion of sheet type membranes to the substrate. Always follow membrane manufacturer’s guidelines for MVER.

6.3 Peel and Stick Membranes

Peel and stick membranes are very similar to sheet type membranes in performance. The major difference between the two styles is that the peel and stick type does not rely on a separately applied adhesive layer to bond it to the substrate. These membranes are generally asphaltic based with a reinforcing fabric on the tile bonding side of the membrane and a removable Kraft paper type backing which exposes a tacky surface once it is peeled away. The installation of peel and stick membranes begins with priming the substrate with a primer specifically manufactured for the purpose. Primers can be either latex based types or epoxy based materials.

Once the primer is in place and sufficiently dry, the removable film is peeled from the back side of the membrane and rolled onto the floor.

Precautions and concerns with sheet type membranes are as follows:

1. Careful consideration must be taken where the seams overlap. Spreading the tile mortar over the seam can be tricky and care should be taken to avoid humps where the tile lays over the seam.

2. These types of membranes have a tendency to soften when exposed to sunlight. Windows exposed to direct sunlight could pose problems for peel and stick membranes.

3. Cleaning regimens also play a factor in whether peel and stick membranes should be used or not. Solvents typically have an adverse effect on peel and stick membranes. Consult the membrane manufacturer for specific applications, installation instructions and cautions.

4. Membrane thickness increases in the folds of inside and outside corners, seams and other transition areas. Additional flashing or skim coating treatment may be necessary to minimize the effects that this can have on the finish tile appearance.

5. High alkalinity can attack and adversely affect some peel and stick type membrane and some adhesives which may be used to adhere the membrane to the substrate.

6. High MVER – generally in excess of 5 lbs/1000 ft2/24 hours (283mg/s m2) can have a negative impact on the adhesion of peel and stick type membranes (follow membrane manufacturer’s guidelines for MVER).

6.4 Recycled Rubber Mat Type Membranes

Recycled rubber mat membranes are primarily designed to be used under interior thin-bed adhesive floor installations as an acoustical underlayment that muffles impact noise through ceramic tile, stone and other hard surfacing materials. These mat types also minimize the transmission of non-structural cracks from the substrate to the tile or stone installation of up to 1/8" (3 mm).

An example of this category type is LATICRETE® 170 Sound & Crack Isolation Mat. This mat is a 1/8" (3 mm) thick rubberized membrane comprised of 88.5% post-consumer recycled materials. This product achieves a ∆IIC rating of 20, per ASTM E2179 “Standard Test Method for Laboratory Measurement of the Effectiveness of Floor Coverings in Reducing Impact Sound Transmission Through Concrete Floors” while meeting ANSI A118.12 crack isolation requirements. It is important to note that this membrane type may not be suitable for most mass transit applications. These recycled rubber mat membranes may be subject to point load and compressive strength issues. Therefore, many of these mat types achieve only a “Residential” or "Light" service rating per ASTM C627 “Standard Test Method for Evaluating Ceramic Floor Tile Installation Systems Using the Robinson-Type Floor Tester”. This means that recycled rubber mat membranes should only be used in residential or light commercial applications, and therefore, would not be appropriate for the majority of mass transit installations.

6.5 Trowelable Membranes

Sound Control

Crack isolation

Waterproofing

Trowel applied membranes come in various forms, including special elastomeric co-polymer types, latex-fortified cement based types, epoxy resin types and urethane types. Great advances have been made in this category in recent years. Some of the trowel applied materials perform as the tile adhesive while providing crack isolation and sound control properties. For example, LATICRETE 125 Sound & Crack Adhesive provides crack isolation protection up to 1/8" (3 mm) in accord with ANSI A118.12 requirements and provides a ∆IIC rating of 15 (per ASTM E2179 “Standard Test Method for Laboratory Measurement of the Effectiveness of Floor Coverings in Reducing Impact Sound Transmission Through Concrete Floors”) while acting as the tile adhesive mortar. LATICRETE 125 Sound & Crack Adhesive is ideal for interior applications where sound deadening, crack prevention or both are required.

Some trowel applied waterproofing membranes include a reinforcing fabric which is used in corners, coves, and to tie into plumbing fixtures (including drains). After the typical pre-treatments are made to cracks and transition areas, the main application normally consists of keying the membrane into the substrate with the flat side of the trowel. This is immediately followed by combing the material in a singular direction, and then finally another pass with the flat side of trowel to smooth the surface. A few key elements are the notches in the trowel act as a gauging device for the membrane. Most membranes require a certain thickness of product to ensure complete waterproofing coverage. As with all waterproofing membranes, trowel applied membranes should be applied at a continuous thickness (as per membrane manufacturer’s installation instructions) to ensure waterproofing integrity. The use a wet film gauge is recommended to assure acceptable uniform thickness.

Latex Cement Based Membranes

Latex cement based membranes are generally comprised of a liquid latex polymer that is mixed with a portland cement based powder. These products are generally very economical in cost and are easy to apply. However, the physical characteristics of these types of products generally restrict their use in demanding mass transit floor applications.

Epoxy Based Membranes

Epoxy membranes are normally 3 component systems consisting of an epoxy hardener, epoxy resin, and a filler powder. These products are generally highly chemical resistant, load bearing and suitable for mass transit applications. Some other advantages to epoxy based membranes waterproofing membranes are as follows:

Flood Testing Can Be Performed in 24 Hours at 70°F (21°C)

Adheres to Metal, Stainless Steel, and Pipe Penetrations

Flexible and Able to Adhere to Many Substrates

Can Be Used as a Flashing Membrane to Tie Into Other Types of Membranes or Surfaces When Required

An example of this category type of waterproofing membrane is LATAPOXY® Waterproof Flashing Mortar.

Urethane Based Membranes

Urethane waterproofing membranes are soft rubbery materials which are usually applied in a minimum thickness of 60 mils (1/16" [1.5 mm]) and may be as thick as 90–125 mils (1/11" – 1/8" [2.3 – 3mm]). Urethane membranes generally cure very slowly and the ultimate finish remains relatively soft and tacky after placement.

These membrane types are usually very chemical resistant and would hold up well under typical chemical attack. However, the disadvantages of the membranes will usually outweigh the advantages. For example, urethane membranes usually do not hold up well under the loads and stresses that mass transit installations experience. This membrane type can creep and deform excessively under load. Therefore, ceramic tile and pavers may not have sufficient support. Consequently, under heavy traffic and point loading, or even normal mass transit requirements, the installation could develop severe cracking of the joints, cracked or broken tiles, and/or loss of bond.

Many tile and stone installations utilizing a urethane based membrane, require a conventional, wire-reinforced, non-bonded thick mortar bed mortar be placed over soft urethane waterproofing membranes and over soft built-up asphaltic type waterproofing membranes.

6.6 Liquid Applied Membranes

Liquid applied membranes offer an ideal solution to the demanding requirements of mass transit applications. In addition, to having “Heavy Duty” ratings as tested per ASTM C627 “Standard Test Method for Evaluating Ceramic Floor Tile Installation Systems Using the Robinson-Type Floor Tester”, liquid applied waterproofing membranes are easy to install and provide many features and benefits. Two examples of liquid applied membranes include LATICRETE® Hydro Ban and LATICRETE 9235 Waterproofing Membrane. Some of the features and benefits include:

Can Provide Both Waterproofing and Anti-Fracture Protection

Meet ANSI A118.10 Standards for Waterproofing

Meet ANSI A118.12 Standards for Crack Isolation

Plumbing Code Approved (IAPMO)

GREENGUARD Approved for Low VOC Content

Thin – Load Bearing and Shock Resistant

Fully Compatible With the Entire Ceramic Tile, Stone or Paver Installation Materials

Fully Formable to Fit Into Tight Areas

Can Be Shaped to Follow Any Substrate Contour

Flood Testing Can Vary According to the Membrane Type and Generally Ranges From 2 Hours to 7 Days at 70° F (21° C) – Check Installation Instructions For Each Waterproofing Membrane For Time to Flood Test

Some Liquid Applied Waterproofing Membranes (e.g. LATICRETE Hydro Ban) May Be Spray Applied With a Commercial, Airless Sprayer (See Section 8.5 For This Methodology).

LATICRETE Hydro Ban is a cold liquid membrane which does not require fabric in the field, coves or corners. LATICRETE 9235 Waterproofing Membrane is a liquid applied, fabric reinforced membrane that is thin, load-bearing, and, like LATICRETE Hydro Ban, is completely compatible with LATICRETE latex thin-set mortars.