Question - Do I need a vapor barrier behind durock?

Answered by: Christopher Perry  |  Category: General  |  Last Updated: 17-06-2022  |  Views: 1350  |  Total Questions: 12

When building a steam shower always use a surface membrane. Per Tile Elfs comments, the USG (Manufacturers of Durcok) stated to me that I don;t need a vapor barrier behind their product. This is especially weird since they DO acknowledge that Durock is not waterproof, but rather water-resistant. 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. You should NOT place a vapor barrier BEHIND the backer board. 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. You need to install a vapor barrier to the studs at the very least, and you must alway mud and tape the seams with fiberglass cement backerboard tape. Backerboard is water-permeable, and will not stop moisture from entering the wall cavity. 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.

https://www.inman.com/2012/02/01/vapor-barrier-tips-walls-floors/

In simple terms, a vapor barrier is a material that won't allow moisture to pass through it, such as plastic sheeting. It's designed to stop the moisture before it can enter the wall cavities. There are two basic types of vapor barriers used with exterior wall insulation. The most common is paper-faced insulation.

https://www.thespruce.com/shower-or-bath-tile-backer-options-4126051

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.

https://www.ecohome.net/guides/2316/the-difference-between-air-barriers-and-vapor-barriers/

In order to prevent condensation from forming, a vapor barrier should be placed on the warm side of your insulation to stop warm, moist air from condensing on a cold surface inside your wall. In cold climates like Canada, for most of the year the vapor barrier should be on the inside of the insulation.

https://www.diytileguy.com/durock-cement-board-waterproof/

“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. Consult local building code for moisture barrier requirements. ”

https://www.diytileguy.com/shower-tile-backer-board/

Tile Backer Board Breakdown Foam boards are lightweight, easy to cut, and a completely waterproof. Pictured: Wedi Board tile backer board. Schluter approves Kerdi over drywall. Hardibacker is the best known fiber cement board. Cement board has improved over the years and is easier to work with.

https://ctasc.com/expert-answers/is-there-supposed-to-be-a-backer-board-gap-above-a-bathtub-flange/

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. Although some say you should have weep holes along this gap so any water behind can weep out into the tub.

https://www.familyhandyman.com/tiling/tile-installation/cement-board-ceramic-tile/

Cement board has a smooth side and a rough side. Face the rough side out if you will be using thin-set mortar adhesive to install the tile but the smooth side out if you will be using latex mastic.

https://www.bobvila.com/posts/93465-hardibacker

cement backer board is not waterproof, but water cant hurt it, even when soaked in water for months or even years

It is important to make sure that a proper vapor barrier (or vapor retarder) is installed on the walls in your bathroom whenever you're building or remodeling. You don't need to put a vapor barrier in the ceiling of the bathroom.

https://www.johnbridge.com/vbulletin/showthread.php?t=83179

A moisture barrier is necessary with any cement board product. If you do not have plastic or roofing felt behind it, then a liquid-applied membrane is in order. Durock is indeed waterproof, meaning it is not harmed by water. But it is by no means a barrier to water.

https://basc.pnnl.gov/resource-guides/walls-behind-showers-and-tubs

Rigid air barrier materials for use behind showers and tubs include fiber-cement, fiber-reinforced gypsum, glass mat gypsum, or fiber mat-reinforced cementitous backer panels.

https://www.custombuildingproducts.com/TDS/TDS-104.pdf

RedGard® is a liquid-applied elastomeric waterproofing material that cures to form a monolithic membrane. Benefits of Product in the Installation. Easy to use and can be applied by roller, trowel or airless sprayer.