Tile Waterproof Membrane

Here’s the deal:  you install tile in bathrooms, kitchens, showers, bathtubs, and other watery places because tile is great at repelling moisture.

But it’s not 100% waterproof.  You’ve got grout seams to deal with, and any kind of seam can let water in.  Not matter how much grout sealant you put on the grout, there is still the chance of water getting through.

If you really want to take care of the problem, install a tile waterproof membrane.

Yes, tile itself in impervious to water.  It’s just the sub-surface (or substrate, whatever you want to call it) that can be damaged.

Polyethylene Sheeting

A good type of inexpensive tile waterproof membrane.  Staple down the poly plastic to the subsurface, then install the HardiePlank or other backer board, then the tile.  You don’t need a million staples, just enough to hold the plastic in place.  More staples mean more chance of water leakage to the sub-surface.

Roofing or Tar Paper

This stuff is el cheapo and comes in big rolls at your local hardware store; always great to have around.  Roofing paper has fallen out of favor because there are “better” things like housewrap, but I think that tar paper still is pretty good stuff.

The tile and thin-set mortar do not install directly on the tar paper!

Instead, staple the tar paper on your sub-surface (like drywall, if you’re tiling a wall), then install your cement backerboard over that.