Regular drywall is a gypsum core coated with a paper covering. Greenboard drywall has specially treated paper to withstand moisture. Builders often install greenboard in areas that have frequent moisture and humidity, such as bathrooms, dank basements and laundry rooms. For greenboard to be effective, you must install it with the correct side facing outward; otherwise, the specially treated paper will face the interior of the wall, where it has no effect.
The green side should face toward you when you install greenboard. The brownish side should face away. Another way to identify the correct side is to install the greenboard so the beveled edges face outward. The beveled edges run the length of the board along the top and bottom. Essentially, they are gentle depressions that make it easier for finishers to embed paper tape over the seams.
If moisture control is vital, greenboard might not be the most effective choice. While it does provide some protection against moisture, it is not as effective as newer types of moisture-control drywall. Typically, greenboard is sufficient for areas far from direct water contact, but is insufficient for areas that might experience splashing, such as above and immediately around bathtubs and shower enclosures.
In the past decade, drywall manufacturers began to sell drywall that features mold resistance and superior moisture resistance. The key difference is the use of glass fiber instead of paper coating, which helps the drywall stave off moisture and mold.
To determine which type of drywall is best for your project, view the manufacturer's recommendations to learn which situations call for the more expensive but more effective types of moisture-control drywall. Another option is to contact a professional drywall installer and ask for a free estimate. Typically, the drywall installer will let you know what type of drywall you need to install.