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.
Install cement board or an equivalent moisture-resistant backing material on walls behind tub and shower enclosures composed of tile or panel assemblies with caulked joints. Don't use paper-faced backer board, i.e., paper-faced drywall, behind seamed tub and shower enclosures.
Best Bathroom Drywall
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.
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.
Once you've removed the old tile, inspect what's behind it. If there's drywall, remove it and plan to replace it with cement backer board to protect the walls from moisture and mold. You can use drywall above the shower head, but anything below the shower head should be lined with cement backer board.
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.
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.
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.
Water can creep through the tile joints and cause damage to the walls behind the tiles. This is why it's important to waterproof the background that you're going to be tiling onto.
You don't have to tear out all of your drywall and install backerboard or anything else, if you have a fairly smooth and flat surface that you're working with.
Tile is meant for a wet area.
Paint and drywall is not water proof, so, overtime you may have problems with mold and decay. The paint and drywall won't perform well in a wet area, like your shower.
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.
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.
Can you use regular drywall in a bathroom ceiling? You can but you will want to coat it in a waterproof paint designated for bathrooms or use a water-resistent drywall instead. Since regular drywall is porous, humid and wet bathrooms can cause mold, mildew, and rotting.
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.
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.
Because of this melamine layer, tileboard is often advertised as a material for bathrooms, even for tub alcoves and showers. But this material is by no means waterproof. Any moisture that reaches the fiber core will make the core swell and bubble, and the damage cannot be fixed.
Many homes have drywall behind the shower tiles. So when water gets behind the tiles, the drywall sucks it up. This causes the drywall to expand, which can put pressure on your shower tiles. Over time, cracks can form in the shower tiles.
A hidden wall leak behind your shower can cause any number of problems. One of the biggest health concerns related to hidden leaks is the buildup of mold and mildew. Drywall impacted by a water leak can begin to grow mold and mildew as soon as 24 hours after exposure.