Best answer
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.
Do I need a vapor barrier behind cement board in shower?
Moisture barriers stop that water or vapor from getting any farther and potentially rotting your studs, the drywall or greenboard installed behind the enclosure. They are required beneath your shower pan and behind your shower walls.
Can you put cement board over concrete?
Technically, cement board can be laid over a concrete slab as the base for a tile installation. ... A better solution is to prepare and resurface the concrete slab so that it can accept thin-set adhesive or a mortar base onto which to lay tile.
How long should cement board screws be?
Cement board attached to plywood or similar underlayment will hold with only 1 1/4-inch screws; for thick or heavy metal fixtures, use 1 5/8-inch screws. In general, 1 1/2-inch galvanized nails will hold the board firmly in place.
Do I need to waterproof cement board in shower?
Here's what the TCNA handbook has to say about the matter: “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.
Do you need plastic behind cement board?
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).
Do you need a vapor barrier behind cement board?
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.
Do you need green board behind cement board?
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.
Do you need to put a vapor barrier behind cement board?
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.
What do you put behind cement board in shower?
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..
Can I mix cement in a bucket?
If you need to mix concrete by hand, there are two options: ... It has all the ingredients dry mixed together for making concrete, i.e. the cement, sand and stone. All you have to do is put it into a bucket, wheelbarrow or on a piece of plastic on the ground, add water and spend a few minutes mixing it.
Related Question Answers

newtover
ProfessorCan I use 1/4 cement board on floors?
Both 1/4- and1/2-inch cement board are appropriate for floors. To install cement board on floors, cement board manufacturers mandate a 5/8-inch plywood subfloor or OSB underlayment.

Will Ness
ProfessorDo you put cement board under a shower pan?
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.

James Lin
ProfessorCan I use plastic cement on resin?
Just do NOT use 'plastic cement' or "liquid cement." This is designed for plastic models, not resin.
It works by partially dissolving the plastic so the parts will fuse together.
Resin does not dissolve so 'plastic cement' will have no effect on it..

Patrick Artner
ProfessorCan you glue stone veneer to cement board?
What can I put stone veneer on for an interior application? For interior applications, stone veneer can be installed over cement board, drywall, and all of the above.

Frodnar
ProfessorCan you put cement board over tile?
Cement board forms a durable, stable base for tile, and it has no organic materials (unlike drywall, greenboard, or plywood) so it is not prone to mold, rot, shrinkage, or decomposition due to moisture. Ceramic tile laid over cement board is one of the most durable floor or wall surfaces you can install.

Joe Phillips
ProfessionalCan you put cement over silicone?
Yes, silicone will stick to cement board.
In fact I highly recommend that you use cement board such as 'Durock' as your backer board.
Use proper screws.
Such as the specific cement board screw..

Andrew Marshall
ProfessionalCan you put concrete in plastic?
According to principal investigator Dr John Orr, introducing synthetics like plastic into concrete generally weakens the material, as plastic doesn't bond to the cement mix like sand does.

t_dom93
ProfessionalHow do you fill gap between cement board and tub?
Technically, after the tile is installed over the backer board that gap between it and the tub ledge should be filled with an ASTM C920 sealant (caulking e.g. silicone). Although some say you should have weep holes along this gap so any water behind can weep out into the tub.

Jorgesys
ProfessionalCan you use 1/4 inch cement board walls?
1/4" Durock cement board should not be used for wall or ceiling applications. For wall or ceiling applications, use 1/2" or 5/8" Durock cement board. If you have 3/8" sheetrock, use 1/2" cement board and feather out the joint to approx 10" to 12". It should be almost unnoticeable if done right.

Lalit Fauzdar
ProfessionalDo I need cement board for stone veneer?
Natural stone veneer is heavy and should not be installed over drywall; cement backerboard or masonry applications are recommended.

Platinum Azure
UserDo I need to prime cement board before tiling?
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.

Mohammad AbuShady
UserDo you need vapor barrier behind cement board?
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.

polm23
UserDoes cement board need to be sealed?
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.

Yuri Schimke
UserDoes concrete stick to plastic sheets?
Cement sticks very well to plastic, or at least Portland cement concrete does. Leave a little residue in a plastic paint bucket, on a plastic tool handle, or on any other plastic surface, and try to get it off a few days later. ... I use wax paper, glass, Teflon sheet, Faux Bone, sheet plastic, Plexiglas, etc.

Evan Teran
UserDoes Loctite Power Grab work on cement board?
It will bond to drywall, plaster, vinyl cove base, polystyrene, polyurethane foam covings, PVC (rigid plastic), stainless steel, glass, wood, plywood, stone, brick, concrete, chip board, ceramics, foam board, cork, and carpet.

vineet
GuestDoes silicone stick to cement board?
Yes, silicone will stick to cement board. In fact I highly recommend that you use cement board such as 'Durock' as your backer board. Use proper screws. Such as the specific cement board screw.30 Sep 2015

Daniel Möller
GuestCan I use cement board for shower floor?
Do not use cement board on its own. Your shower will leak and you will be tearing it out within a year.

Eric
GuestCan I plaster over electrical cables?
No problem plastering straight over cables but if you think you might ever want to pull them out put some plastic capping over them first.

Sdaz MacSkibbons
GuestCan you use plastic anchors in plaster walls?
Plastic wall anchors don't work with lath and plaster walls. Instead, use plaster anchors made of metal like a molly bolt or a toggle bolt. Be sure to use one that's long enough to get behind the plaster and lath. When drilling into plaster, you'll need to use a masonry bit.

apangin
GuestWhy is my cement cracking?
When concrete is still in its plastic state (before hardening), it is full of water. When that water eventually leaves the slab, it leaves behind large voids between the solid particles. These empty spaces make the concrete weaker and more prone to cracking.

ForEveR
GuestWhat thickness cement board should I use?
Half-inch cement backer board is ideal for most tiling jobs, including walls, floors, countertops, and ceilings.
For flooring, the backer board should be installed over a 5/8-inch thick OSB or plywood base..

Matthew Layton
GuestWill silicone adhere to cement board?
Yes, silicone will stick to cement board. In fact I highly recommend that you use cement board such as 'Durock' as your backer board. Use proper screws.

Charlie Martin
GuestDo I need cement board for kitchen backsplash?
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.

Steven Lu
GuestDo you put cement board under bathtub?
You don't need any cement board under the tub. It is far more important to have a sturdy layer of ply under the tub.

senderle
GuestShould I cover new concrete with plastic?
Plastic Sheeting Can Permanently Discolor Concrete. Adverse weather conditions such as rain, snow, or freezing temperatures often make it necessary to protect concrete by covering it. ... That's what makes curing concrete with plastic so effective: the plastic keeps the concrete damp.

Inanc Gumus
GuestIs a vapor barrier necessary behind cement 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. ... You should NOT place a vapor barrier BEHIND the backer board.

kevnk
GuestCan I reuse cement backer board?
Undamaged cement backer board does not need to be replaced. If tile has not been attached directly to the backer board, and it has not been dented or punctured, it can be reused without any special preparation.

Black Raven
GuestDo I need plywood under cement board?
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).

pearpages
GuestDo you have to put Thinset under cement board?
No Thinset underneath the backer board “The thinset goes ON TOP of the cement board to stick the tiles!” ... Cement board is a different product and it needs to be installed in its own way. Additionally, screws don't take the place of thinset either.

Thaoaaaaa
GuestShould I put cement board under tub?
You don't need any cement board under the tub. It is far more important to have a sturdy layer of ply under the tub.

pypmannetjies
GuestShould I put Thinset under cement board?
Embed the cement board in latex-modified thin-set mortar The main reason for using thin-set between the cement board and the subfloor isn't as much for bonding as it is for even, void-free cement board support throughout the floor. ... Then spread thinset mortar with the flat side of a 1/4-in.

Alper t. Turker
GuestShould you put a vapor barrier behind cement board?
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.

nwellnhof
GuestWhat do you put on seams of cement board?
Use special mesh tape on seams Cut drywall to fill in between the existing wall or ceiling and the cement board. Screw the drywall to the studs. Cover all of the corners, joints and seams, including the joint where drywall and cement board meet, with the fiberglass mesh tape.

Ilya
GuestWhat is the best insulation for under a concrete slab?
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.

avdeluca
GuestIs cement board the same thickness as drywall?
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.

Craig McQueen
GuestWhy do you cover concrete with plastic?
Covering the curing concrete with plastic keeps it cleaner, but there is a more important purpose behind this practice.
...
To prevent cracks, plastic is placed over the curing concrete to trap the water inside and regulate its temperature, ensuring gradual curing..

Brian Campbell
GuestCan I use Kerdi band on cement board?
First Kerdi can be installed on drywall or cement board. However if installed on drywall it is only protecting one side.

Oliviena
GuestCan you store cement in a bucket?
Place the bag in an airtight tub or buy premix concrete in a bucket. If you need to store a bag of premix concrete, you should put it in an airtight plastic container. Even if the bag is not open, the relatively porous material of the bag can let in air and moisture, allowing the mix to age.

Mike 'Pomax' Kamermans
GuestCan you caulk cement board in shower?
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.

Hogan
GuestDo you have to glue down cement board?
You cannot put a cement backer board over that. You need to put a layer or plywood, minimum 5/8 IIRC, over those boards, then mortar the backer to the plywood. Those 1x8 boards won't give a solid foundation and will flex. Over time, that will cause tile to pop loose or crack.

kohske
GuestHow much space should be between cement board and tub?
1/4"The backer board should overlap the tub flange so the tile has a stable backing to attach to. This requires shimming the backer board out from the studs so the wall is plumb. There should be a 1/4" gap between the tub ledge and the backer board.

Jean-François Fabre
GuestWhere do you put cement board in a bathroom?
Cement backer board is mainly used as a sub-surface for tiling. Cement backer board is often used as a tile base on plywood or OSB subfloor. Cement backer board on concrete as a subfloor or underlayment is usually not recommended or needed. In most cases, you can apply tile directly to the concrete.

Eric Guan
GuestCan I just screw down cement board?
Put thinset beneath your backerboard. And put your dog out. Once you have the area fully covered with thinset you can lay your backerboards into the bed of thinset and screw it down. DO NOT use drywall screws!

Rudie
GuestHow high should cement board be in shower?
Start installing your boards a quarter inch above the floor, tub, or shower board and caulk accordingly. 2. Fasten cement board with specified nails or screws, a maximum of 8” on center at all supports.

Prune
GuestShould I cover concrete with plastic?
Rapid Moisture Loss Is Your Enemy Covering the curing concrete with plastic keeps it cleaner, but there is a more important purpose behind this practice.
...
To prevent cracks, plastic is placed over the curing concrete to trap the water inside and regulate its temperature, ensuring gradual curing..

ccpizza
GuestShould I cover my concrete with plastic?
Rapid Moisture Loss Is Your Enemy Covering the curing concrete with plastic keeps it cleaner, but there is a more important purpose behind this practice. ... To prevent cracks, plastic is placed over the curing concrete to trap the water inside and regulate its temperature, ensuring gradual curing.

Tonnie
GuestShould I put cement board under tile?
If you want to replace an old, cracked tile floor or other type of flooring with new ceramic tile, it's absolutely imperative that you create a solid setting base for the new tile. If you're working over a wood subfloor, cement board is the right choice for your tile base.

Andrzej Pronobis
GuestShould I put wire mesh in concrete slab?
Wire mesh makes concrete more durable and increases its strength. The area in which the concrete will be laid down should be covered in mesh before pouring commences.

ux.engineer
GuestShould you cover fresh concrete with plastic?
Covering the curing concrete with plastic keeps it cleaner, but there is a more important purpose behind this practice. ... To prevent cracks, plastic is placed over the curing concrete to trap the water inside and regulate its temperature, ensuring gradual curing.

Kip
GuestShould you put plastic under concrete slab?
Recently, though, research has shown that the old traditional layer of 6-mil Visqueen (polyethylene plastic) under the slab is seldom effective for two main reasons: Although it may seem water-tight, this grade of material allows a lot of water vapor to pass through.