As in many modern houses, our en-suite shower is made up of tiles fixed onto plaster board. Over the years this has started to leak as the grouting failed, and the plaster board has become soggy and needs replacing. We have had two suggestions from different builders. One suggests ripping out the old plaster board and replacing it with quot;cement boardquot; onto which tiles would be stuck. The other suggestion involves cutting out the old plaster board, replacing it with new plaster board which would then be quot;sealedquot; before tiles are stuck onto it. Does anyone know which of these would be the better option please? Costs of both proposals appear to be similar so we really want the better engineering solution.
Plasterboard, or drywall, is paper over a gypsum core. Durock, or cement board, is fiberglass mesh over a concrete base. Not only is the cement impervious to water, the rougher surface is a MUCH better base for the tile to adhere to. I would never use anything else under tile.
Remove the old plaster or green board and install 1/2 inch Durock(cement board). Then stick the tile to the new cement board.
Both systems would work. I think the cement-board option is a little bit better. But if you want to be really sure the shower will last your lifetime. Ask the cement board contractor if he will seal the cement board before he installs the tile. Don't ask him how much extra he will charge right off let him bring that up - but expect it to cost a little more. If the floor of the shower is tile as well insist on the sealer. as well as cement board. Most contractors don't like tile floors, they tend to go with preformed one piece bottoms - highly recommend that.
I am no expert other than the re-muddling I have done around my own home, but I would say that the cement board route would be the better way to go. No matter how well sealed the plaster board is, it will eventually draw moisture due to the constant exposure over the years. Before the plaster board is installed, the shower pan should be installed. The plaster board is then installed to sit just off the lip on the inside of the shower pan but not above the edge of the pan. When they install the cement board (which, by the way, is used as exterior siding on homes in the south) make sure they tape and seal all the joints, a process similiar to installing wallboard, but done with a mesh tape and mortar, instead. A reputable drywaller or tiler should know to do this, but I would make sure ... this is no time for misunderstandings. Water damage inside a house can cause a multitude of problems, not the least of which is the shower coming through the downstairs ceiling one night when the boss is over for dinner.
I run a construction company. We swear by cement board and don't even use plaster board anymore. attached is a partial article on why green board is being phased out: Contractors take note: “greenboard” is being drummed out of the tile industry as a ceramic tile substrate in wet areas. Though traditional greenboard has a moisture-resistant gypsum core and moisture-resistant paper facings, over the years more durable, water-resistant products have been developed that perform better and ensure fewer water-related failures. In fact, Kieren Corcoran, national product manager for Georgia-Pacific Corp. noted the 2006 International Residential Code (IRC) further accelerates the trend away from greenboard stating, “Water-resistant gypsum backing board [greenboard] shall not be used where there will be direct exposure to water.” (Section R702.3.8.1) The 2006 IRC goes on to say that “Cement, fiber cement or glass mat gypsum backers in compliance with ASTM C1288, C1325 or C1178 and installed in accordance with manufacturer’s recommendations shall be used as backers for wall tile in tub and shower areas and wall panels in shower areas.” (Section R702.4.2) To date, 45 states have adopted all or part of the IRC for tile backers. Corcoran noted that many of the installation steps are the same for all backer boards that meet the 2006 IRC: All are approved for wet areas All must be installed over dry, well-braced studs All require non-corrosive fasteners, although fasteners vary depending on manufacturer’s recommendations All require some type of joint treatment. The most common method is the use of 2 inch glass-fiber mesh tape embedded in a skim coat of mortar over joints and corners.
