Do I need a waterproof membrane under tile on a concrete floor?
Different contractors give contradictory advice about whether a liquid waterproofing or crack isolation layer is actually necessary under thinset. This leaves homeowners guessing whether to apply a membrane or lay tile directly over the concrete, risking moisture damage or cracked grout if they choose wrong.
What people tried
Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.
- 1consulting multiple tile stores and contractors to compare conflicting installation recommendations
- 2searching online for installation guidelines
- 3asking for guidance on community forums
In their words
Unedited, most upvoted first, each linked to the thread it came from.
“First of all I have NO experience with anything tile or shower related, but we’re having our shower redone and thought it would be really helpful to ask for advice/guidance here.”source ↗
“Just a little confused on what the actual right path is here.”source ↗
“I want to tile a mud room in my basement, one place I called said they would like "paint" something underneath the tile and thinset (I think a membrane? Or some other sort of waterproofing? I don't know for sure), another place said we didn't need anything.”source ↗
“Getting ready to install a floating engineered hardwood floor over a dry plywood subfloor and looking for recommendations for underlayment.”source ↗
Where this came up
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