Do I need a vapor barrier behind cement board in shower?

Their online instructions/diagrams show no use of a vapor barrier. You should, so that any moisture that gets behind the cement board runs into the tub or shower instead of into your wall cavity (causing rot or mold/mildew).

You still need a vapor barrier with cement board, although in this case the barrier can go behind the board. Cement board is heavy enough and breathable enough to take the moisture without a problem. By having the vapor barrier behind the cement board you stop the moisture going further into the wall.

Because cement board can be used either for floors or walls, the surface below the cement board will vary: ... In such wet areas, never install cement board directly over drywall or green board. Instead, first, remove the existing surface material, then install the cement board over the studs and membrane, as applicable.

You should NOT place a vapor barrier BEHIND the backer board. Where, pray tell, would any such collected vapor/water go? Answer:There's nowhere proper for such moisture to egress. The current best practice is to place waterproofing OVER the backetboard and just UNDER the tile.

Cement Board and a Liquid Membrane No plastic sheeting goes behind the cement board.

A liquid waterproofing membrane, such as RedGard or Hydro Ban, is applied to the cement board and allowed to cure.

Then, tile is installed over the membrane..

Cement backer board is also called cement board, and it's the most commonly used backer board for all manner of ceramic and porcelain tiles. Made of cement and reinforced on the top and bottom with fiberglass, this waterproof backer board is generally used for tiled shower surrounds and floors in wet areas.

In showers, the standard substrate is tile backer, also called cement board or cement backer board. Ceramic and porcelain tile, more than almost any other surface material, needs a stable, flat, flex-free substrate. Even the slightest amount of movement in a building structure can telegraph to the tile and crack it.

Once the subfloor of proper thickness is properly installed then you can apply cement board directly to the subfloor material. ALL CEMENT BOARDS MUST be installed in a fresh bed of thinset. ... If you want the cement board under the shower tray then do so - doesn't matter.

Glass mat gypsum board is a better choice. Sheets of glass mat gypsum are made from water-resistant silicone-treated gypsum, reinforced on both sides by fiberglass mats. DensShield is one common brand. It is easier to cut than cement board, it is mold resistant, and it has a built-in moisture barrier.

You could just add a couple inches of sand, enough to handle the vapor barrier and then cover the pipe with a couple layers of plastic or roofing material and place the concrete right over the pipe.

Most exterior slabs do not need a vapor barrier. ... In general, place the concrete slab directly on top of the vapor barrier, with the subbase below. ... The vapor barrier can be placed under the subbase, if the building is closed in when the dry subbase material is placed.More items...

Cement Board and a Sheet Membrane Kerdi can also be installed directly over standard drywall in a shower because, when installed correctly, it creates a continuous waterproof barrier..

JRC3 Member.

It will need to be lined or it will wick into the slab and studding.

The liner also makes the walls around the pan water-tight, that's why the liner normally goes up at least 3" above the pan behind the tile and backer material.

Moisture gets behind the wall tile and is eventually caught by the liner..

You will have to ensure that there is no wax, oil, grease, or soap scum on the face of the concrete slab that could ruin or reduce the bond. After that, I recommend that you install a sloped shower pan to contain the shower water and prevent harmful organisms from becoming resident in the surrounding walls and floor.

It is rolled out between the actual laminate flooring planks and the subfloor.

Very often, particularly in a below-grade installation on a concrete basement floor, a vapor barrier is recommended in addition to the underlayment.

That vapor barrier would go between the subfloor and the underlayment..

Despite a successful moisture check and the presence of an underground moisture barrier, you still need additional protection from water vapor before laying a wood floor. Sheets of 6-mil thick polyethylene plastic, overlapped with seams taped, is one means of providing that moisture barrier.

Natural stone veneer is heavy and should not be installed over drywall; cement backerboard or masonry applications are recommended.

Do I need to prime HardieBacker® board before I tile onto it? No. HardieBacker tile backerboard is ready to tile once installed, just wipe down with a damp sponge to remove any dust prior to tiling.

Concrete bases need an underlay with a moisture barrier, a damp proof membrane (DPM) or a separate barrier to protect the floor from damp. If the sub-floor is wooden the choice of underlay will depend on what is being laid on top.

plaster is not a vapor barrier, so any odors in the walls can get in. it's good for the longevity of the plaster since it can breathe (if it gets wet, it can dry, for instance), but it won't keep the odors out.

Although most backerboards currently available won't fall apart when exposed to moisture and are somewhat water-resistant, they aren't waterproof.

To prevent moisture from seeping through to the wood or metal studs beneath the tile, a barrier or sealant must be used on porous materials..

The wallboard must be installed 1/8 inch above the shower pan. If the shower pan is not in place, the wallboard height must be guessed, which can lead to inaccuracies and an expansion gap that is too large or too small.

JRC3 Member. It will need to be lined or it will wick into the slab and studding. The liner also makes the walls around the pan water-tight, that's why the liner normally goes up at least 3" above the pan behind the tile and backer material.

The Surface Below the Cement Board Flooring: For ceramic tile floors, the cement board usually rests on a plywood subfloor (minimum 5/8-inch-thick exterior-grade plywood or OSB). ... In such wet areas, never install cement board directly over drywall or green board.

Although most backerboards currently available won't fall apart when exposed to moisture and are somewhat water-resistant, they aren't waterproof. To prevent moisture from seeping through to the wood or metal studs beneath the tile, a barrier or sealant must be used on porous materials.

If it's a cement board, you need a vapor barrier, because cement retains moisture, which means the wood next to it is always damp.

While you don't always need to seal backer board, it sometimes make sense to do so. If you are installing backer board in an area that will be subject to a great amount of moisture, like in a shower, then it makes sense to put a waterproofing sealer on it.

You don't need to seal a concrete floor before installing laminate; however, to prevent moisture from the concrete floor from affecting your laminate, install a vapor barrier of polyethylene film. Install this barrier even if the concrete subfloor is covered by vinyl, linoleum, terrazzo or ceramic tile.

Do not use cement board on its own. Your shower will leak and you will be tearing it out within a year.

But for a tile backsplash, if your wall is good and plumb, without any major ridges or problems, you don't always need to use a backer board, often you can just apply thinset to the walls and put your tiles in place.

If you're working over a wood subfloor, cement board is the right choice for your tile base. No matter what you're told at a home center, it's not a good idea to install tile directly over plywood, especially in a damp area like a bathroom.

Methods Used to Stop Moisture in Concrete FloorsLow-permeance Vapor Barrier or Retarder.

A Low-permeance vapor Barrier or retarder can effectively keep below-slab moisture from reaching the flooring system.

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Allow Natural Drying of Concrete Slab.

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Keep Excavation Free of Water..

Cement board is heavy enough and breathable enough to take the moisture without a problem. By having the vapor barrier behind the cement board you stop the moisture going further into the wall. ... You should NOT place a vapor barrier BEHIND the backer board.

No plastic sheeting goes behind the cement board. A liquid waterproofing membrane, such as RedGard or Hydro Ban, is applied to the cement board and allowed to cure. Then, tile is installed over the membrane.

“A waterproof membrane or vapor retarder membrane must be specified to prevent moisture intrusion and protect adjacent building materials.” ~B412 Bathtub or shower with prefabricated receptor. Cement board or Fiber-cement board. Ceramic Tile. ... Consult local building code for moisture barrier requirements.”

Creating an insulation layer and a vapor barrier between the concrete slab and the ground beneath it is the best practice in insulating basement floors.

The insulation barrier will help keep warm air in, and the vapor barrier will keep unwanted moisture out..

Because cement board can be used either for floors or walls, the surface below the cement board will vary: Flooring: For ceramic tile floors, the cement board usually rests on a plywood subfloor (minimum 5/8-inch-thick exterior-grade plywood or OSB).

Linda CottinStep 1: For holes larger than 1/2-inch in diameter, use a carton knife or carbide-tipped tool to cut a V-shaped groove behind the edges of hole. ... Step 2: Use a clean, damp sponge to wipe down the area to be patched.Step 3: Mix up a small amount of thin-set mortar following the manufacturer's instructions.More items...•

You still need a vapor barrier with cement board, although in this case the barrier can go behind the board. Cement board is heavy enough and breathable enough to take the moisture without a problem. By having the vapor barrier behind the cement board you stop the moisture going further into the wall.

Applying a bead of polystyrene-compatible caulk or mastic to the top of the insulation board minimizes water infiltration behind it. For under-slab applications, the rigid foam insulation typically should be installed over a gravel base, with a poly vapor diffusion retarder between the gravel and insulation.

Whereas drywall comes in 4-by-8 sheets, cement board comes in 3-by-5 sheets. ... The smaller dimensions of cement board make the installation of it on large walls more difficult, but cement board panels fit vertically in 3-foot wide showers, or horizontally behind a standard 5-foot bathtub.

This DUROCK® cement board is a non-combustible, water and mold-resistant panel designed for use under tile, in shower areas, and readily applied over ...

The use of a vapor barrier (more accurately termed a vapor retarder), having a water vapor permeance of less than 0.3 perm is frequently used to retard the flow of moisture through the slab. These vapor retarders are typically polyethylene or polyolefin sheeting materials.

Actually, no. Air barriers need to be continuous and free from holes, but vapor barriers do not need to be. Lots of vapor moves by air movement, not a heck of a lot of vapor moves by vapor diffusion. The concrete slab is the air barrier, and the ripped and torn and punctured polyethylene sheet is the vapor barrier.

Any gaps or cracks in your concrete floor and walls need to be sealed with cement. Special concrete coatings or a polyethylene membrane can also be applied as a barrier.

It can be, but it's not really necessary. You can tile directly to drywall in any dry area. If your doors go all the way to the ceiling, you might consider cbu verses any kind of drywall on the ceiling, otherwise, it is considered a dry area.

Combining a basic mortar mix with sand and Portland cement will create a good dry pack concrete. All of these mixes create a strong water resistant barrier for your shower floor and tile. Ahead we'll discuss each option in more detail.

The application of vapor barrier in exterior concrete is unnecessary due to the fact that water penetration does not matter. Any slab on grade that is enclosed and on the interior of a building should have a vapor barrier installed prior to pouring concrete, especially if flooring will be applied.

In California they place sand between slabs and plastic vapor barriers—in Florida they don't. Almost everywhere (except “California”) that slabs are placed on the ground—a plastic sheet—a vapor barrier—is located directly under the concrete slab and on top of the ground (Photograph 1).

In the event the caulk seal between the bottom row of tile and the tub/shower fails, water can get behind the tile. If the backer board is touching this ledge, it will readily soak up this water like a sponge. ... Then, before installing the tile, apply a bead of pure silicone caulk between the backer board and the ledge.