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Do I need to add Mapei Mapelastic AquaDefence over the plywood or over the hardiebacker or none?

I’m installing the flooring tiles in the laundry room. I am going to have hardiebacker screwed to plywood and tiles applied on hardiebacker. Do I need to add a coat of moisture prevention over plywood or over hardiebacker?

What is recommended?

Thank you!

Dan
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  • Do you have a floor drain? – Ecnerwal Apr 07 '22 at 15:25
  • No, I do not have a floor drain. – Dan Apr 07 '22 at 15:36
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    Wow I wonder what we did before all these fancy and expensive membranes we’re available? Oh I remember we sealed the tile. I haven’t been a fan of coatings / membranes, well I use plastic on shower stalls some of the ones I did in my youth are still solid mid 70’s so maybe I am set in my ways I use thinset on the sub floor to help hold my backer with screws, back butter tiles and really fill the grout lines using addmix after the grout is cured seal and then even regular moisture is not a problem. – Ed Beal Apr 07 '22 at 19:51

2 Answers2

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AquaDefence is the last layer before tiles are applied.

Tape & cement the seams, cement the (sunken) screw heads. You can use your tile thinset for this. Then apply AquaDefence to cover it all.

AquaDefence is applied in several thick coats with a thick 15-20mm roller, not thin like primer or paint.

P2000
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  • liquid applied membranes is a good concept but if you have to trust something over the long run I have a hard time envisioning a liquid applied membrane that would provide more tear resistance than a fleece backed factory created membrane. If something settles or shifts liquid applied is going to tear. – Fresh Codemonger Apr 08 '22 at 01:12
  • @FreshCodemonger sure, but I'm answering the question, and AquaDefence is vendor approved for floors. – P2000 Apr 08 '22 at 03:21
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If I was going to do a membrane I'd use a fleece backed membrane. I'd never trust a liquid applied membrane on a horizontal surface.

I suppose if the option is no membrane or a liquid applied membrane then maybe I'd opt for the liquid applied membrane.

If you are already tiling the floor then I'd consider an epoxy grout that will effectively make the tile floor water proof.

This sounds like a laundry room that is located on a floor that is not the lowest in the house.

Ultimately if a water hose or the machine breaks in such a way that water is rushing out it won't make much of a difference if the floor has a membrane as the river will flow into other rooms. If there is a slow drip or something the membrane might have some value but generally a washer pan is going to be way more effective for that.

I tend to be over cautious when planning / designing washer spaces on non ground floors. I have done shower pan installation (kerdi) with tiled curb and the washer sits in the shower pan. I don't do that anymore - the traps tends to run dry and it is a lot of work.

My preferred installation method now is:

  1. Use a waterproof base flooring (concrete or tile).
  2. Use cellular pvc baseboards ( impervious to water )
  3. Keep drywall 1/2" or more above floor level or use concrete board / tile backer board.
  4. Put the washer in a pan
  5. Use the flood stop washer solenoid valves and put the sensor into the pan near the water hookups.

There are also some sensors now that if they detect water can send you a text message.

Fresh Codemonger
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  • Perhaps you know this already, but for floor traps that run dry you can use a "trap primer". Whenever the washer (or hot water tank, or toilet) uses water, the primer deposits a little bit into the trap. – P2000 Apr 07 '22 at 23:29