Custom Building Products' RedGard is a liquid-applied elastomeric product that serves as a waterproofing and anti-fracture membrane.

On Jan. 13, 1993, the American National Standards Institute (ANSI) approved a standard for load-bearing, bonded, waterproof membranes for thinset ceramic tile and dimensional stone installations. Specifically, the standard is ANSI A118.10-1993.

An important point to know is that adherence to American National Standards is completely voluntary. The existence of this standard does not preclude anyone from manufacturing, marketing, purchasing, or using products or processes that do not conform to standards.

ANSI A118.10-1993 applies to trowel-applied, liquid and sheet membranes. The test protocol also covers fungus and microorganism resistance.

The degree to which a product is waterproof is determined by use of the ASTM D-4068 Annex A2 Hydrostatic Pressure test modified. A key element of ANSI A118.10 is that the membrane not only must pass the hydrostatic testing, it also must comply with shear requirements for the tile specified by undergoing the Robinson Floor tests.

Many if not all waterproofing membranes also serve as anti-fracture membranes when used under ceramic tile and dimensional stone.

Waterproofing membranes are most often used on balconies, food courts, exterior decks and elevated walkways, and commercial kitchens. In fact, I have even seen membranes used on flat roofing surfaces being converted to ceramic-clad recreation areas. Membranes are used where waterproofing is needed in above-grade situations to provide lower-level protection from water.

It has been my opinion that most waterproofing membranes used have been those that come in sheet form. Perhaps that's because their installation appears to be simple.

National Applied Construction Products' Strataflex waterproof membrane is a self-bonding elastomeric sheet that also functions as an anti-fracture membrane.

Sheet products

Sheet-applied waterproofing membranes may be made of varying materials and compositions. For example, membranes may be made of vinyl, polyethylene or a polymer-modified bitumen - just to name those with which I am personally familiar.

All have a scrim so that ceramic tile or stone can be bonded to the membranes using thinset mortar. The bonding of the sheet membranes to the substrate also varies. In use today are latex adhesive bond coats, thinset bond coats and, in one case, the membrane is self sticking (although it does require a primer coat prior to membrane installation).

A time-saving feature of sheet membranes is that they allow ceramic tile or stone installations to commence on the same day that the membrane is applied. In addition, I am familiar with at least one firm that says its sheet membrane has not only waterproofing and anti-fracture properties but also meets sound-control requirements - both for Sound Transmission Class (STC) and Impact Insulation Class (IIC) - as well.

Another member of the sheet membrane family is a unique structure of polyethylene with a grid structure of square cavities. This product is installed according to the thinset mortar method. The manufacturer also claims that it provides a vapor pressure-equalization layer to accommodate moisture from the underside of the substrate.

Other membrane types

Trowel-applied membranes are another alternative to the sheet variety of products. Some trowel-applied membranes include a Portland cement, additive and mat in their system. Other trowel-applied products utilize only the liquid itself. This particular product, which also can be listed under the liquid category, also claims to be effective in providing a slab-on-grade moisture barrier for resilient flooring installations.

Liquid-applied membranes may or may not require reinforcing fabrics. Most such products do. Liquid-applied membranes may be composed of latexes, urethanes or bitumen. Generally speaking, liquid-applied products are applied by using a paint roller. However, some are trowel applied and then flat troweled to obtain an even and complete coverage of the substrates.

Because of the wide variety of systems available today, it is wise to carefully consider not only the material cost but the labor cost for installation, the need for immediate installation of your ceramic tile or stone, the product warranty, and certainly the limitations of the product.