IF YOU'RE ONE OF THE THOUSANDS of builders who uses paper-faced greenboard as a tiling substrate in showers and tub surrounds, things are about to change. Starting Jan. 1, 2006, the International Residential Code (IRC) will no longer approve greenboard as a tile backer in wet areas and will instead recommend cement-based backer boards or non–paper-faced moisture-resistant products.

Greenboard is a paper-faced, water-resistant gypsum board that is used as a backing for ceramic, plastic, and metal tile in tub, bathroom, and shower areas. But code officials and other manufacturers are concerned that the product may be inadequate if water breaches the tile installation.

“If water never gets behind a [tiled wall], it is not an issue,” says Barry Reid, product development marketing manager for Atlanta-based G-P Gypsum. “There have been some [greenboard installations] that lasted a long time,” Reid continues. “The risk of water getting to the greenboard is still very high.” Chicago-based USG believes that greenboard shouldn't be used in showers, tub surrounds, and other wet areas since it was not designed for that.

Though the IRC will prohibit greenboard in wet areas, builders have alternatives. G-P, for example, is touting its DensShield glass-mat gypsum products as a perfect alternative that can be scored, cut, and installed like regular gypsum.

Cement-based backer boards are effective options for tiling in wet areas, but gypsum-based panel manufacturers say the products are heavier and must be cut with a reciprocating saw. As a result, cement-based panels are harder to install. Gypsum-based panels, can be scored and cut with a utility knife.

So, how much will the rule change cost? Reid says the cost could be negligible. “A builder would be looking at about $20 more per bathroom,” he says.

The code change language is written in a 2004 supplement, but it will be in the general codes in 2006.