Tile is bonded with thinset to the surface of the membrane. The internal make-up of this membrane is such that movement in the concrete is not directly transferred to the tile.
Although the membrane is bonded to the concrete and the tile to it, the membrane stretches where needed to prevent or reduce force transference.
These membranes are either trowel applied or sheet applied. In many cases, multiple components or steps are part of the system. Performance varies also - it is important to check with the crack isolation membrane manufacturer regarding their installation instructions and intended use.
Can roofing felt or scribing felt be used as an anti-fracture membrane? Some contractors have used felt paper as an inexpensive type of anti-fracture membrane. Unfortunately, this type of installation generally does not provide suitable bond strength between the tile and the floor, does not hold up to moisture, and can promote fungal growth. Products made specifically for crack isolation are sold for everything from isolating the tile from shrinkage cracks to tiling over control joints to protecting the entire floor from potential cracking in the concrete.
When used to cover the entire floor, many manufacturers will warrant the entire floor installation, including the cost of replacing and installing new tile. This movement occurs when a fault or deficiency below the concrete shifts, causing an up-and-down motion.
No manufacturer will warrant its products over this type of movement. An architect or engineer should be consulted to recommend corrective measures. Cracking is limited to horizontal planar movement of the substrate.
It is particularly important when dealing with a cracked substrate that expansion joints are properly located and filled with a suitable sealant or prefabricated expansion joint. Movement joints in the substrate shall be carried through the tile installation.
The individual manufacturers, project engineers and architects should be consulted, per Tile Council of North America TCNA , regarding their requirements for expansion and control joint material and placement.
Membranes covered by this definition are bonded to a variety of manufacturer-approved substrates covered by ANSI specifications.
In some cases, the trowel-applied products can be used as the adhesive for the tile. Other products within the scope of this category are allowed to cure or are applied as sheet goods and are then used as the substrate for the tile. Membranes may be sensitive to naturally occurring moisture and alkalinity when used over cement- and gypsum-based substrates.
Consult the manufacturer for acceptable limits of moisture and alkalinity. Some manufacturers may require that a primer be applied to the substrate and allowed to dry prior to the installation of the membrane. The sheet membranes may be dry-backed or self-adhesive. The dry-backed products are usually installed using an adhesive or thinset mortar.
The sheet materials may also be a peel-and-stick, meaning that the adhesive is already applied to the back of the membrane and covered with a temporary protective paper. When properly aligned, the paper is removed allowing the adhesive to bond to the substrate. The thickness of the liquid, once applied, normally must be measured by using a wet film thickness gauge, as shown in Photo 1. The manufacturer may require that two or three coats be applied to reach the minimum thickness requirement.
Portland cement-based materials are trowel-applied and designed to bond to the substrate and the tile while allowing movement to be absorbed within its body.
As concrete cures, the moisture escapes through the top surface into the usually drier air while the underside remains wet. This moisture differential causes the concrete to shrink and curl, producing cracks. Many times, the concrete surface is cut to provide a stress relief in the surface, known as contraction or control joints.
These cuts may be tooled into the wet concrete as it is being finished or saw cut within 24 hours. I normally use the primer first, it sticks like mad when the primer is used. I've told the story here a couple times but once I put some on a balcony that was poured with light weight concrete and had a few cracks.
About the time we got it stuck down a thunderstorm come overhead and it rained real hard for at least 30 minutes. This way the tile would be even with the bricks. The membrane was under water in those areas where it held water along the edge.
We swept the water off and I pulled at a corner of the membrane, still well bonded. I like the stuff. I don't know if Protecto-wrap makes it for Dal-tile or not, seems like the same stuff to me. They make it in 3ft rolls too. Im not sure if 1' is wide enough to work and dont think its warrented unless your 3 times tile size. All times are GMT
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