Tile Troubleshooting: Membrane Terminology
Included in the "15 New Methods" for 2005 are F125-05 and F125A-05, which address crack isolation membranes. You need to study these very carefully when considering specifying, selling or installing these systems.
This is a very important study and work is being done to improve membrane technology in our industry. I think it is imperative to note that often times we celebrate the advancements in technology that the tile manufacturers have made. I hear it all the time at trade shows and seminars. Advancements in porcelain tiles, glass and metal are often cited, and they should be. But I want to salute the allied industry as well, for keeping pace with the tile manufacturers and continuing to provide new products that allow our trade to continue on its incredible growth pattern. Such is the case with membranes today.
The NTCA Technical Committee, along with the Materials, Methods and Standards Association (MMSA) and the Tile Council of North America are among several organizations that are spending a lot of time and effort on standards and methods in order to keep pace with technology. The reasons for the adoption of standards of performance are clear. Without specific criteria relating to the performance of these products, inferior systems potentially can be sold and installed, possibly resulting in failed installations.
In a new document recently approved by the NTCA Technical Committee for inclusion into The NTCA Reference Manual, specific types of membranes for the tile industry were thus defined:,br>
Cleavage Membranes are incorporated into a ceramic tile installation when the backing surface can be damaged by water, is not continuous, is cracked or is dimensionally unstable. The cleavage membrane is designed to separate the backing surface from the mortar setting bed and tile, allowing the setting bed to be unbonded and free floating; thereby not subject to the instability of the backing surface. When a cleavage membrane is incorporated, the setting bed is reinforced with lath or wire. Cleavage membranes can be roofing felt, reinforced asphalt paper, polyethylene sheeting, chlorinated polyethylene sheeting, polyvinyl chloride membrane or high solids, cold liquid applied membrane. Specific requirements for these materials can be found in the American National Standards for the Installation of ceramic tile (ANSI A-2.1.8)
Crack Isolation Membranes
Crack Isolation Membranes for thin-set ceramic tile and dimension stone installations act to isolate the tile or stone from minor, in-plane substrate cracking. These membranes may be bonded to a variety of substrates approved by the manufacturer. The contractor should check with the manufacturer to determine the limitations of crack movement the specific material will tolerate. There are two basic types of crack isolation membranes; sheet applied and trowel or liquid applied.
These are usually provided in rolls consisting of a flexible material with some amount of elasticity that allows the material to elongate while remaining bonded to the substrate. Some of these sheet- applied membranes have reinforcing fabrics adhered to the surface of the membrane to enhance the tensile strength of the material as well as provide a better bonding surface for thin-set mortars.
Liquid Applied Membranes
May be single or multi-component membranes applied in a liquid or paste form. Some are trowel applied; some may be applied with a paint roller or even spray applied. Some liquid applied membranes require embedding a fabric into the membrane to increase tensile strength. These membranes cure into a continuous crack isolation system allowing direct bonding of the tile, usually with latex Portland cement mortar.
ANSI Specifications governing Crack Isolation Membranes are currently under development and should be in print very soon. The TCA Methods of F125 and F125A mentioned earlier in the article is for specifying application of Crack Isolation Membranes. Method F125 addresses existing in-plane cracks and the material is applied only in the vicinity of the existing cracks. F125A is for specifying the Crack Isolation Membrane to be applied throughout the installation to protect against existing cracks as well as future in-plane cracking that may develop. Careful attention must be paid to whether or not a caulked joint should be applied to one or both sides of a crack being isolated with a membrane. Please consult with the manufacturer for these recommendations.
Waterproof Membranes for thin-set ceramic tile and dimension stone installations function as barriers to positive liquid water migration. In architectural circles, when a membrane is subjected to a perm rating test, it is considered to be waterproof if it results in a perm rating of 1 or less. Most waterproof membranes in our industry are not considered vapor barriers. The will stop liquid water penetration from entering the substrate. However, most waterproof membranes do allow some penetration of moisture vapor through the membrane. In addition to built-up membranes, non metallic, lead or copper waterproofing normally applied by the plumbing trade, there are also waterproof membranes available for use in both thick-bed and thin-set installations on vertical or horizontal applications which can be applied by the tile contractor. Sheet Applied and Liquid Applied Membranes are among the systems that can be bonded to a variety of manufacturer-approved substrates.
ANSI Specifications governing Waterproof Membranes can be found in ANSI A118.10. Significant work is currently being done by this committee, so please pay close attention to any changes that may take place on document in 2006.
Moisture barriers are designed to reduce or eliminate moisture migration from the substrate (normally concrete) into the flooring adhesive, setting material, or the flooring material itself. The term moisture barrier is a bit misleading and most of these membranes do not provide an absolute barrier for moisture contained in the normal vapor flow through concrete substrates. They function more as a moisture vapor retarder because they do allow some moisture to penetrate the membrane but at a substantially reduced rate than untreated concrete would. These membranes are normally associated with the resilient flooring industry that sets limitations on the amount of moisture flow allowable prior to the installation of resilient products. These limitations are set because excessive moisture may cause warping of wood products, mildew growth under sheet vinyl or VCT or even deterioration of adhesives normally associated with these products. When tested for moisture migration with a standardized calcium chloride test, many manufacturers of resilient materials require the moisture flow to be less than five pounds per 1000 square feet in twenty-four hours and some require less than three pounds. Moisture barriers can reduce excessive moisture flows to within allowable limits.
Most moisture barriers are liquid applied. Some are applied to a topical membrane from a continuous membrane on the surface of the substrate and some are applied as a penetrating material which fills the pores of the concrete thereby reducing the avenues available to moisture flow. Other materials used as moisture barriers penetrate and use some of the constituents of concrete to induce crystalline growth; thereby increasing the density of the concrete itself and reducing the flow of moisture.
Moisture flow under twelve pounds per 1,000 square feet is normally not considered detrimental to a ceramic tile installation installed with standard dry-set mortar. Tile set with latex Portland cement mortars should be concerned with moisture flow above ten pounds. But if readings are this high or even higher, I strongly urge you contact the setting material manufacturer for their recommendations on how to proceed. High moisture readings may be an indication of other trouble, such as hydrostatic pressure, green or uncured concrete or moisture being introduced to the concrete from an outside source.
These are usually applied throughout the area being tiled and they separate the finished surface from the substrate to allow the independent movement between the two and prevent the transfer of stresses to the tiled surface. The relief of stresses incurred by in-plane crack movement, thermal expansion and contraction, or moisture expansion occurs as a result of incorporating air cavities into the membrane. These air cavities remain empty as the membrane is bonded to the substrate on the bottom and the setting material and ceramic tile are applied to the surface of the membrane. These air cavities absorb the differential movement between the substrate and the tile and setting material. When the stresses decrease, as with thermal expansion and contraction, the membrane returns to its original configuration without loss of bond to the substrate or the tile.
This term has been used for years, and it was clear in our committee meetings that the definition meant different things to different people. In an attempt to clarify the situation, Anti-Fracture Membranes are now referred to as Crack Isolation Membranes, with the two definitions of types already covered in this article and adopted as methods in the TCA Handbook for 2005.
Vapor Barrier Membranes
These are sheet membranes that have a perm rating close enough to zero that are considered vapor barriers. These membranes do not allow the penetration of normal vapor gases, much less liquid moisture. Waterproof membranes are not normally considered to be vapor barriers. They will let moisture in a vapor form penetrate the membrane. Vapor barriers will not. Because of this, careful consideration should be given when incorporating a vapor barrier into a ceramic tile installation, as improper placement of such a barrier may result in moisture condensation within the wall cavity, creating deterioration of building materials.