Moisture Resistant Plasterboard

What Is Moisture Resistant Plasterboard?

Moisture-resistant plasterboard is high-performance sheet material engineered to withstand the challenges of moisture-laden environments. From steamy bathrooms and busy kitchens to laundry rooms and utility spaces, it provides a dependable solution where ordinary plasterboard would quickly degrade.

At its core is a dense gypsum formulation enhanced with water-repelling agents such as silicones or waxes. This treated core is encapsulated between two tough paper liners, with the outer face specially coated to further resist moisture ingress. 

Though not fully waterproof, moisture-resistant (MR) plasterboard significantly limits water absorption, offering a critical barrier against the slow creep of moisture that can undermine structures, cause mould growth, and compromise air quality.

Equally versatile as it is resilient, MR plasterboard serves as an ideal substrate for ceramic tiling in wet zones - such as showers and splashbacks - or as a base for plaster finishes in rooms where humidity is variable. 

Composition & Performance

Moisture resistant plasterboard is comprised of three fundamental layers: a central core and two paper facings.

• Gypsum Core: Unlike standard plasterboard, the gypsum core is not plain. It is infused with a precise mixture of additives during its formation. These typically include silicone and/or wax-based water-repellent agents. This infusion process ensures that the entire core has built-in moisture resistance. If water vapour were to penetrate the outer paper layer, these additives prevent the gypsum crystals from readily absorbing the moisture, which is what causes standard board to soften and lose its strength.
• Paper Liners: The board is sandwiched between two layers of heavy-duty paper. The outer layer, which is characteristically green, is specially treated to be water-repellent. This green liner acts as the first line of defence, causing water splashes to bead up and run off rather than soak in. It also has a lower water absorption rate than standard paper facings, slowing the ingress of ambient humidity.

How to Identify MR Plasterboard

On any construction site, it's crucial to be able to quickly identify the right materials. Manufacturers make this easy for moisture resistant plasterboard. Look for the following key feature:

• Green Paper Facing: The most common and immediate identifier is its distinctive green-coloured paper liner. This colour coding is an industry-standard signal that the board has been treated for use in damp environments. While the exact shade of green may vary slightly between brands, it is the universal indicator for moisture resistance.

Always double-check the product description and specifications printed on the board or its packaging to confirm it meets the requirements for your project.

Applications

• Bathrooms and Shower Rooms: As a backing for tiles in splash zones and for the general wall and ceiling surfaces.
• Kitchens: Particularly behind sinks and around cooking areas where steam is prevalent.
• Utility and Laundry Rooms: To combat the humidity generated by washing machines and tumble dryers.
• Basements and Cellars: In converted underground spaces that may be susceptible to dampness.
• Cloakrooms and WCs: In smaller, often less ventilated, toilet facilities.
• Garages: In attached or integral garages that can be prone to damp.

It is important to note that for areas subject to constant and direct water exposure, such as inside a shower enclosure, a specialist cement-based tile backer board may be a more appropriate choice.

Benefits

• Prevents Structural Damage: Its primary benefit is the prevention of moisture absorption. This protects the plasterboard's gypsum core from weakening, crumbling, and sagging over time, maintaining the structural integrity of your walls and ceilings in humid conditions.
• Inhibits Mould and Mildew Growth: By significantly reducing water absorption, you deny mould and mildew the damp environment they need to thrive. This leads to a cleaner, healthier living space and better indoor air quality, which is particularly important for individuals with allergies or respiratory conditions.
• Provides a Durable Base for Finishes: It offers a stable and reliable substrate for both tiling and painting. Tiles adhere more securely to a board that doesn't degrade with moisture, and paint finishes are less likely to peel, blister, or stain.
• Increases Longevity of Interiors: Using the right board in the right place extends the life of the entire wall or ceiling system. This reduces the likelihood of needing disruptive and costly repairs in the future, making it a wise long-term investment.
• Cost-Effective Preventative Measure: While the initial outlay is slightly higher than for standard plasterboard, this cost is minimal when compared to the expense of remediating a wall damaged by damp and mould. 

Installation and Handling

The installation of moisture resistant plasterboard is similar to that of standard plasterboard. It can be fixed to timber or metal studwork using galvanised or corrosion-resistant screws to prevent rusting.

Installation Considerations:

• Fixings: Always use corrosion-resistant fixings to ensure a secure and long-lasting installation.
• Jointing: For a seamless finish, the joints between boards should be filled with a water-resistant jointing compound. A fibreglass mesh tape is recommended for reinforcing the joints in damp conditions.
• Cutting: The boards can be cut using the traditional score-and-snap method with a sharp utility knife.
• Ventilation: It is crucial to ensure that the room has adequate ventilation to allow moisture to escape, as the plasterboard is resistant, not impervious, to moisture.

Finishing and Decoration

Once installed and the joints are filled and sanded, moisture resistant plasterboard can be decorated to match the desired aesthetic.

• Sealing: Before painting or tiling, it is good practice to apply a suitable primer or sealer. This will provide a uniform surface and enhance the performance of the final finish.
• Painting: For painted finishes, it is advisable to use a paint specifically designed for bathrooms or kitchens, which will offer further protection against moisture and mould.
• Tiling: Moisture resistant plasterboard provides an excellent, stable background for ceramic tiles. A waterproof tile adhesive and grout should be used to ensure a fully water-resistant system.