What workarounds did people try for "Do I need a waterproof membrane under tile on a concrete floor?"?

Community members documented 13 workarounds: 1. consulting multiple tile stores and contractors to compare conflicting installation recommendations 2. searching online for installation guidelines 3. asking for guidance on community forums 4. Adding 1/2" plywood to the subfloor 5. Following the installation specs in the TCNA handbook 6. Checking the installation guide provided with the tile 7. Posting on the r/Tile subreddit for advice 8. Hiring a different contractor who is comfortable with the preferred product 9. Using 3/4 inch tongue and groove OSB or Advantech panels. 10. Adding a decoupling membrane on top of the subfloor. 11. Gluing down a second layer of OSB on top of thin plywood to stiffen the floor. 12. Returning the padded underlayment and relying only on the flooring's attached pad 13. Using just a simple thin vapor barrier over the concrete instead of a padded underlayment

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.

Overview

Last updated Oct 30, 2026

People affected8 accounts across 2 forums

Workarounds found13 items attempted

Community agreement10 total upvotes

What the numbers show

Counted from the threads quoted below. How we count

The most recent one is from October 2026.
This comes up 31.7× more often in r/Flooring than across the site as a whole.

What people tried

Every workaround mentioned in the threads below. We haven’t tested any of them — and nobody here is claiming they worked.

13 items+ Contribute

Found another way around this?

Share your steps and trade-offs so fellow engineers don't have to reinvent the wheel. No account required.

1
consulting multiple tile stores and contractors to compare conflicting installation recommendations
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2
searching online for installation guidelines
Did this help you?
3
asking for guidance on community forums
Did this help you?
4
Adding 1/2" plywood to the subfloor
Did this help you?
5
Following the installation specs in the TCNA handbook
Did this help you?
6
Checking the installation guide provided with the tile
Did this help you?
7
Posting on the r/Tile subreddit for advice
Did this help you?
8
Hiring a different contractor who is comfortable with the preferred product
Did this help you?
9
Using 3/4 inch tongue and groove OSB or Advantech panels.
Did this help you?
10
Adding a decoupling membrane on top of the subfloor.
Did this help you?
11
Gluing down a second layer of OSB on top of thin plywood to stiffen the floor.
Did this help you?
12
Returning the padded underlayment and relying only on the flooring's attached pad
Did this help you?
13
Using just a simple thin vapor barrier over the concrete instead of a padded underlayment
Did this help you?

Tried another approach not listed above?+ Share your workaround ↑

In their words

Unedited, grouped by where they were said, most upvoted first within each place, each linked to the thread it came from.

r/HomeImprovement4 people · September 2026 – October 2026

“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 ↗

crayonzbox · r/HomeImprovement · 3 upvotes

“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 ↗

CulturalLab2031 · r/HomeImprovement · 2 upvotes

“Getting ready to install a floating engineered hardwood floor over a dry plywood subfloor and looking for recommendations for underlayment.”source ↗

YsaboNyx · r/HomeImprovement · 1 upvotes

“Im getting ready to lay flooring down in my new home (Lifeproof Heirloom Pine) with a concrete subfloor and bought quietwalk lv for my underlayment, when i bought it and was researching i was reading I would be okay using it, now im seeing it would be to soft and my floor would eventually fail, so would I be okay using it or should i return it and just use a vapor barrier?”source ↗

SilverPlatimun · r/HomeImprovement · 1 upvotes

r/Flooring4 people · September 2026 – October 2026

“But our GC is insisting on using backer boards and keeps on telling me that he has been "using this for years" and "never had issues". Maybe he is just used to the backer boards and has never used decoupling membranes.”source ↗

“What should I do? Am I over thinking this? Or should I insist on a decoupling membrane?”source ↗

anonphoenix_ · r/Flooring · 1 upvotes

“I am planning on tiling a suspended timber hallway floor with limestone and removing the current floorboards to replace with either 18mm ply or OSB and I’m unsure if ply is the better choice and if it needs to be Marine Ply which is significantly more expensive.”source ↗

Stokehall · r/Flooring · 1 upvotes

“I had ply floors 1/2” which were too much flex for tile.”source ↗

v1nn1r · r/Flooring · 1 upvotes

“I should be good with narrow crown 7/8 18 gauge staples right? Or do I want screws?”source ↗

“Also what about thin layer of vapor barrier over this underlayment, under the lvp.”source ↗

Imaginary_Air_2514 · r/Flooring

Where this came up

r/Flooring r/HomeImprovement bathroom renovation contractor disputes diy flooring home improvement home renovation installation materials tiling