Do I really need a membrane between my bathroom subfloor and tiles?
Asked by RandomUser1234
Hey everyone! We're in the process of remodeling our bathroom and have completely ripped out the old flooring down to the studs. We've laid down plywood and are about to install Hardie Board, followed by tiling. The Hardie Board instructions suggest tiling right onto it, but I've heard from Lowe's that I should use a membrane like Schluter-DITRA for added flexibility and to handle expansion and contraction. I also have a DIY book that says a membrane isn't necessary. I'm wondering if we really need this membrane, if it's just an upsell, or if it's a good safety measure.
Answers
Using a decoupling membrane is a good safety net. Just make sure your seams are taped and sealed correctly. Don't forget that neither tiles nor grout are actually waterproof, so without a proper membrane, you could still face issues down the line.
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Hardie Board can handle water pretty well, but they won't stop moisture from reaching your plywood underneath. If you're okay with height, you might want to use a membrane like Kerdi right over the plywood instead of Hardie. Just something to think about!
TileMaster256: I appreciate that! I hadn't thought about the waterproofing aspect until you mentioned it.
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Definitely consider using a decoupling membrane with Hardie Board. While it's usually okay, the membrane can help with movement and prevent cracking in your tiles, especially if you're tiling a bathroom where water might play a role.
BathroomRenovator99: Thanks for the insight!
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FixItPro567: Thanks for the reminder! We're definitely trying to avoid mistakes like the last guy did.