The backer board is in a position to provide much-needed support for the shower system by working as structural sheeting. On top of that, it will create a secure bonding surface for tile, thin-set mortar, and waterproofing membrane as well.
Special protection is needed behind showers and tubs to prevent moisture from seeping into the wall structure. Use an appropriate waterproof or moisture-resistant backing material behind grouted tile or stone or segmented plastic or fiberglass tub and shower surrounds.
Whenever installing tile in any area of your house, you need a special substrate or base layer. In showers, the standard substrate is a tile backer like cement board or some type of sheet or liquid membrane that protects the shower stall's underlying structure from water.
When sheetrock is used in the shower area it will most likely fail due to the fact that it is moisture resistant and not water proof. Once water infiltrates under the tile sheetrock becomes susceptible to water damage and may crumble.
It is critical to safeguard the components beneath against vapor and water damage. Fiberglass-coated gypsum board eliminates the need for any type of moisture barrier. In this instance, even so, a concrete backer board may be ideal. This is because it is more durable and stronger than a gypsum board.
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.
Green Board No-Go's
Shower stalls, saunas, steam rooms, and tile-backed bathroom applications put green board at risk of becoming saturated. Not only can the water damage that can accrue from direct water contact cause mold issues, but green board has also been proven to be slightly weaker than standard drywall.
The short answer to the question is, “It's not recommended.” However, this answer only really only suffices if you're converting a room that was never a bathroom into a wet space. Drywall on its own is not suitable for use in bathrooms because it is prone to absorbing moisture and thus losing structural integrity.
There is no other benefit than cost. 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).
For shower and bath surrounds, use cement board. Cement board is appropriate for direct contact with water, and you can tile over it. The best bathroom drywall for walls and ceilings includes green and purple board. Both offer moisture resistance and are intended for high-humidity areas.
Walls: Use 1/2-inch or 5/8-inch-thick cement board, not 1/4-inch. The extra thickness is needed when spanning the studs and it provides a solid base for the tile. Countertops: 1/4-inch, 1/2-inch, or 5/8-inch-thick panels are all suitable for countertops.
What is a shower tile backer board? A shower backer board can act as a waterproofing barrier in between your shower and the wall. Traditional shower wall boards are made out of Portland cement, and they also come along with fiberglass reinforcements.
You do not need to protect the entire bathroom with cement board, no. However, the cement board and tile should extend past the tub/shower at least a little bit so that drywall isn't the first victim of excess water splashing out.
The Tile Backer Board creates a smooth foundation to be tiled upon as well as being extremely compatible with a variety of tiles such as marble, limestone, granite and much more. Its versatility makes it suitable for floors, walls and can also fit into awkward spots and corners with curved backer boards.
As long as a concrete slab is very flat and contains no cracks, tile can be installed directly on top, using thinset as the adhesive, allowing you to skip the backer board layer.
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.
There are no restrictions for interior walls, but some suggest that maximum weight should not exceed 15 lbs. per square foot. Larger and heavier tiles will require anchoring with mechanical fasteners.
Greenboard drywall is a type of drywall with a paper facing that has been treated with a waxy coating and chemicals that resist moisture and mildew. It is well suited for finishing walls in humid locations, but should be avoided for very wet locations, such as showers and tub surrounds.
Purple drywall is both mold and moisture resistant, and is another great choice to use in bathrooms, but it's much more forgiving than green board when it comes into contact with water. You can use purple drywall for the ceiling and/or upper walls of a shower, for example.
Space prone to moisture such as bathrooms and laundry rooms are also typically most prone to mold – which can be disastrous and costly to the structure of your home. Walls and ceilings in these spaces that are often damp due to humidity or splashing are suitable for mold-resistant drywall.
When using a standard cement board for a waterproofed shower enclosure, installers must also apply a liquid waterproofing membrane on the entire wall structure. With PermaBASE WP, they need to apply waterproofing/sealant only at joint seams, fastener heads/penetrations and exposed edges.
Green Board. Green board is a paper-backed, water-resistant drywall that has a light green "hospital" tint. It is an older form of water-resistant drywall that is gradually being phased out in favor of products that combine both moisture resistance and mold resistance.
For bathroom applications, green board can be used on ceilings and walls where there is no direct water application, such as behind sinks and on bare walls. Only cement board can withstand the wear and tear of a shower or tub enclosure.