Picking the Right Drywall for Bathrooms & Basements
Greenboard vs. PURPLE® vs. Cement Board
Moisture has a way of finding every weak point in your walls. That’s why finishing a bathroom or basement is never just about paint color; it’s about what’s behind the paint. Use the wrong drywall, and you’ll be patching, repainting, or worse, treating mold before the next season rolls around.
Let’s compare the big three: greenboard, PURPLE®, and cement board, and figure out once and for all which belongs in your shower, which belongs in your basement, and which belongs nowhere near either.
Not All Wet Is Created Equal
Homeowners frequently group “moisture” as a single category, but bathrooms and basements handle it very differently. A shower wall gets soaked daily, while a basement might never be splashed but still struggles with humidity.
Your choice of drywall should depend on how much water exposure it will receive and how often. This is where the “color-coded” drywall system is useful.
Grasping this distinction is crucial. Remember that…
Direct water hits surfaces like shower walls or tub surrounds day in and day out.
High humidity fills the air in bathrooms and below-grade spaces, soaking into porous materials over time.
Damp conditions exist in laundry rooms or half-baths that never see a splash but still need protection.
Greenboard
Once upon a time, greenboard was the go-to for “wet” rooms. Its paper facing has a waxy, moisture-resistant coating, giving it a leg up over regular drywall. But decades of real-world use (and a few too many soggy bathroom remodels) revealed its limits.
Greenboard works well in areas that only get damp, such as half-bath walls, laundry rooms, or ceilings above showers. But when it’s exposed to direct or prolonged moisture, the gypsum core eventually absorbs water, softens, and becomes a breeding ground for mold. That’s why today’s building codes ban greenboard from use inside showers or tub surrounds.
PURPLE® Drywall
When humidity is your enemy, PURPLE® drywall is your hero. Made by National Gypsum, this material combines moisture, mold, and mildew resistance into one sleek purple package. It’s become the modern replacement for greenboard in most residential bathrooms and for good reason.
PURPLE® drywall uses advanced coatings that block mold spores from taking hold, even in damp air. It’s ideal for bathroom walls, ceilings, basements, and laundry rooms, where humidity levels fluctuate. You can paint it, texture it, or tile over it (in non-shower areas) just like standard drywall.
But, and this is important, PURPLE® drywall is not waterproof. It won’t crumble from a little steam, but it can’t handle direct, repeated water exposure. If it’s getting splashed daily, you’ll need something stronger.
Cement Board
If drywall is like basic armor, cement board is the titanium kind. Made from cement and reinforcing fibers, it resists rotting, swelling, or disintegrating regardless of water exposure. That’s why professionals rely on it for shower tile bases, tub surrounds, and backsplashes.
Cement board doesn’t break down when wet, but it isn’t waterproof. It absorbs moisture, which can reach framing or insulation if not sealed. Professionals always use a waterproofing membrane, like a thin, rubberized barrier applied as a coating or sheet, to keep walls dry.
Done right, a cement board wall can handle decades of showers without complaint. Done wrong, no membrane, unsealed seams, and you’ll end up with water behind your tile and a mess behind your walls.
Bathrooms vs. Basements
The biggest mistake homeowners make? Treating bathrooms and basements the same.
Bathrooms are about direct water management. Your biggest risk comes from spray, leaks, and condensation. Basements, meanwhile, are about controlling air moisture and humidity.
In a bathroom, cement board rules the shower, while PURPLE® drywall covers the rest. Greenboard? It can survive in powder rooms or ceilings outside the splash zone, but modern builders often skip it altogether in favor of PURPLE®.
In a basement, the threat is slow, steady dampness. Here, PURPLE® drywall or other mold-resistant panels shine. They won’t absorb that heavy summer air or grow mildew behind the paint. Combine them with proper insulation and ventilation, and you’ll keep that “basement smell” out for good.
Details That Make or Break the Job
Even the best drywall can fail if the details are wrong. Tiny mistakes, such as a missed seam, the wrong compound, or a misplaced vapor barrier, can undo all your careful material choices.
Seams and screw holes on cement board must be sealed with a waterproof joint compound or tape. Waterproofing membranes must overlap properly, especially around corners and fixtures. And never double up vapor barriers: if you put one behind the wall and a waterproof layer on top, you’ll trap moisture inside, creating the perfect conditions for mold.
Painting too early is another common pitfall. Drywall compound needs time to cure before you prime, and the primer itself should be labeled mildew-resistant to match your moisture-resistant substrate.
The Hybrid Option
You might also hear about DensShield® or other coated glass-mat drywall products. These hybrids combine a waterproof surface with a mold-resistant core and are approved for tiled shower areas.
They’re a great alternative when installed exactly as the manufacturer specifies, but skip a step, and their waterproof promise vanishes. If you’re hiring a contractor, ask what backer they’re using and whether it meets ASTM C1178 standards for wet areas.
Match the Board to the Battle
There’s no one-size-fits-all solution, only smart combinations. Cement board is the shower choice, PURPLE® wins in humid spaces, and greenboard has been demoted to light duty.
When you match the right material to the right environment, your walls stay beautiful, your air stays clean, and your next remodel won’t start with a musty smell.
Ready to Ditch the Guesswork?
At Custom Paint & Finish, we’ve repaired every type of drywall disaster, peeling paint, hidden mold, and even full bathroom rebuilds caused by the wrong materials. Our team can evaluate your space, spot the hidden moisture threats, and install the right drywall system for each zone.
Whether you’re finishing a basement, remodeling a bathroom, or building new, we’ll make sure your walls stand up to whatever Northern Indiana humidity throws their way.
Give us a call or send us a message, and let’s build something that lasts.
