Hi guys, I'm about to tile my bathtub surround and have some questions regarding moisture barriers. I already have the 1/2 durock cement board and 6 mil plastic sheeting. Before I put up the plastic sheeting on the studs, I wanted to double check to see what people thought was a better moisture barrier... Redgard painted directly onto the cement board or the 6 mil heavy duty plastic sheeting attached to the studs. If you pick one over the other, can you tell me why? Is there a difference in how well each one will protect from long term moisture problems? It would be nice to hear the pros/cons to Redgard vs the plastic sheeting.I'm debating whether or not I should just go buy some Redgard and leave my plastic sheeting for another purpose. But if they both offer the same long term protection, then I'm happy just sticking with my plastic sheeting since it will save me a trip to the store and I am more familiar with that as a moisture barrier.
The problem with using a paint-on barrier like Redgard is that if you miss a spot or if there are any breaks in the application, you have an entry point for moisture. Plastic sheeting on the other hand, is continuous and will seal uniformly unless there's a breach in it such as a cut or puncture. I would think the plastic sheeting would be easier to apply. That would be my choice.
I've done a whole lot of this work over the years. Redgard is the best product I've ever seen for a moister barrier It's the standard for shower / tub surrounds. It's easy to use and will protect for a lifetime. Hang your cement board with the proper screws. Tape the seems and corners with fiberglass tape. Paint the redgard over the entire surface. Let dry; you know it's dry because it will turn from pink to red in color. Add another coat (or two) over the seems and corners to make sure the seems are sealed. Let dry. Install your tile or stone using thin set mixed with polymers. When you grout make sure to mix your grout with polymers. I know some guys who will use thin set to mud the seems before taping. This works well if you have some bigger gaps, but redgard is pretty thick stuff, like pudding. This type of installation will insure no water gets back behind your walls and will last a lifetime. Plastic has the issue of nail / screw holes, trapping water, and condensation. Redgard dose not because it is a moister barrier that you can lay tile directly on. There are other options and systems, but they tend to be more costly and harder to install. On a side note: I find redgard dose not apply well with a roller. It's very thick. I like to use a large brush. Plus a brush helps insure a good thick coat.
