In wet areas, which board is recommended instead of standard gypsum board?

• A. Lath & Plaster
• B. Type X Gyp
• C. Portland cement boards
• D. MMR Gyp

Answer: (C)

In wet areas, the substrate behind tile must resist moisture and stay stable. Standard gypsum board is paper-faced and absorbs water, which can cause swelling, deterioration, and mold growth—making it a poor base for showers or tub surrounds. Portland cement boards, or cementitious backer boards, are designed for moisture exposure. Their cement-based core is far less absorbent, they don’t swell like gypsum when damp, and they provide a solid, stable surface for tile adhesion. That durability is why they’re the recommended choice in wet areas. Lath and plaster is an older method that isn’t ideal for modern tiled wet zones, and Type X gypsum board is fire-rated but not inherently moisture-resistant. Cement boards are specifically suited for moisture-prone environments, which is why they’re preferred here.