Can Kerdi be installed over plywood?

Asked By: Guiayara Kruhs | Last Updated: 26th April, 2020
Category: home and garden indoor environmental quality
5/5 (124 Views . 40 Votes)
-Schluter told me Kerdi can not be put over plywood that it prohibits it from breathing and will move.

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Also, can you put Kerdi over cement board?

First Kerdi can be installed on drywall or cement board. However if installed on drywall it is only protecting one side. Kerdi really offers very little advantage over hardiboard plus membrane.

Furthermore, can Kerdi be installed over drywall? Yes. Once you install KERDI over the drywall panels, they will be completely protected from the water and vapor in your tiled shower.

Besides, can you lay tile on plywood?

While tile can be laid on plywood, do not install tile directly onto the plywood subfloor itself. Use intervening layers of two sheets of plywood.

Do I need a vapor barrier behind Kerdi?

Kerdi is the vapor barrier, there is no need for anything behind it. Kerdi can even be installed over drywall. Cement board and grout are not water proof, if there's Kerdi no moisture is ever going to be able to get behind it. The weak points in the system are always in the corners where one wall meets another.

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Is Kerdi better than cement board?

First Kerdi can be installed on drywall or cement board. However if installed on drywall it is only protecting one side. The back side of the drywall fails and it is just as bad or worse than if it had an issue on the tile side. Kerdi really offers very little advantage over hardiboard plus membrane.

Will RedGuard stick to Kerdi board?

1) No, it won't interfere with the performance or adversely effect it. RedGuard is not harder to adhere to. There is no reason to use both products although it can be easier to use the RedGuard in corners and niches without the build up you can get with kerdi.

How much does Kerdi board cost?

Only 9 left in stock - order soon. I liked the KERDI-BOARD-SC curb because it does not need to be wrapped in Kerdi membrane as it is already waterproof.

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Can you tile over Kerdi membrane?

Unmodified thin-set mortar is recommended to set ceramic and stone tile, including large format tiles, over the KERDI membrane. Since KERDI is impervious, it does not deprive the mortar of its moisture.

Can you paint over Kerdi membrane?


Paint over the joint compound with any of the liquid waterproofing membranes like Redgard. You'll be fine. You could also use an exterior primer paint or even shellac. Then install the KERDI.

Is Kerdi board strong enough?

Remember, after tile is installed, only shear (vertical) forces will be on those tiles and properly installed Kerdi is more than strong enough to handle it. ANSI requirements for Kerdi is minimum 50 psi bond shear strength at 7 days, 170 psi membrane breaking strength - plenty strong for what you're installing.

How do you attach a Kerdi membrane?

Apply thin-set mortar to the substrate using a 1/4" x 3/16" (6 x 5 mm) V-notched trowel or the KERDI-TROWEL, which features a 1/8" x 1/8" (3 x 3 mm) square-notched design (Note the open time of the mortar). Press KERDI fully into the bond coat.

How thick is Kerdi membrane?

KERDI is 8-mil thick and has a water vapor permeance of 0.90 perms, when tested according to ASTM E96, using Procedure E at 90% relative humidity. KERDI-DS is 20-mil thick and features additives to produce a water vapor permeance of 0.18 perms.

Do I need to prime plywood before tiling?

Priming Wooden Floors
You must “overboard” floorboards with a suitable thickness of marine grade plywood (not the cheap “sheathing” ply you can get) - basically, the thicker the better (12-18mm), as this will give the floor more rigidity. The plywood surface will then be the surface to be tiled.

How thick should Plywood be under tile?


British Standards recommend a minimum of 15mm thick plywood to be used for over-boarding purposes (any less will not provide the rigidity required). This involves screwing a sheet of plywood over the top of the existing floorboards / chipboard or plywood to provide extra rigidity and a flat surface onto which to tile.

What is the best underlayment for tile?

Exterior plywood is an acceptable underlayment for tile and is preferred to interior-grade plywoods because the bonding adhesives used are waterproof. If water seeps through the tile installation to the underlayment, it will not cause the wood to swell, as happens with interior-grade plywood.

How do you attach tile to wood?

Glue, called mastic, is the least expensive method for installing tiles. Mastic adheres the tile directly to a wooden sub-floor, to a wooden back-splash or onto a piece of plywood.

How do you prepare a concrete floor for tile?

Start by sweeping your concrete floor to get rid of all dust and debris. Then clean with a wet mop of plain water. Use a few tablespoons of a degreasing cleaner in warm water and scrub the concrete with a scrub brush. Finally, rinse thoroughly.

Can I use modified thinset with Kerdi?

Modified thinset mortars aren't recommended for use with Kerdi because they must dry out to gain strength, whereas the membrane inhibits drying, which can lead to unpredictable results. For example, if a shower is used before the mortar has cured properly, leaks and polymer leaching can occur.

How much is the Kerdi shower system?


Price: $187.50
The Schluter Kerdi-Shower-T trays are made of lightweight, expanded polystyrene (PS40) for constructing mortar-free shower bases and feature center drain outlet designed to integrate with the Schluter-Kerdi-Drain.

Can you use thinset on Sheetrock?

Thinset bonds best with a porous surface, such as new drywall or backerboard, which needs no preparation, but you can apply it over painted walls or tiles that are flat and in good condition as long as the shiny finish is removed. Use the type of thinset mortar specified for your particular tile.

Can you tile a shower on drywall?

The bottom line is that drywall (and this includes moisture resistant drywall) should never be used behind tile in wet areas (showers and tub-shower combinations). This is especially important in a shower located on an outside wall, but also helps even if the shower is on an inside wall.