By Sean Gerolimatos, Director of Research and Development, Schluter Systems
If you’re planning on using an uncoupling membrane in your next tile installation, then here are the answers to three frequently asked questions:
How do I remove the memory from the membrane roll?
A roll of sheet-applied uncoupling membrane can hold memory or shape, sometimes causing it to bounce or curl during installation, especially at the end of a roll. The easiest solution is to:
Step 1: Bring the matting up to room temperature.
Step 2: Measure and cut the material needed.
Step 3: Back-roll the section to take out the memory.
How do I stop chalk lines from rubbing-off?
Chalk lines are commonly used to mark the floor and matting during installation. However, since many sheet-applied membranes are made of plastic, the chalk can be rubbed-off easily. To stop this, try:
Option 1: Spray hairspray over the lines. You don’t have to worry about this acting as a bond-breaker because the thin-set is mechanically locked into the inlays on the topside of the uncoupling membrane.
Option 2: Use an ink line instead.
How do I achieve proper thin-set coverage?
Full thin-set mortar coverage is essential for ensuring a secure bond and support for the tile. There are three steps to this:
Step 1: Ensure Correct Mortar Consistency
When installing the membrane, ensure the thin-set mortar is mixed to a fairly fluid consistency, but still able to hold a notch. If the mortar is too thick, it may not transfer to the underside of the membrane as required.
Step 2: Mortar Application
Apply thin-set to the area where the matting is to be installed using the correct trowel (make sure to check manufacturer directions for the correct trowel size).
Apply a thin layer of mortar with the flat side of the trowel to produce solid contact with the substrate. Then, comb additional mortar using the notched side of the trowel. When combing mortar, hold the trowel at a 45-degree angle. If pulled at a lower angle, this can mean less mortar in place, resulting in poor coverage. Combing the mortar in one direction also helps, making it easier to collapse the mortar ridges when embedding the membrane.
Step 3: Embedding the Sheet-Applied Membrane
First, apply the sheet membrane down and solidly embed using a float or a roller. Make sure to observe the open time of the thin-set. If the mortar skims over, remove and reapply before installing the membrane.
Then, lift a corner to check coverage. You should see full contact between the underside and the thin-set mortar. Re-embed the membrane. If full coverage has not been achieved, remove and verify proper mortar application then reapply the membrane.