How to Build Wet Room Walls and Floors?

Wet rooms are a luxurious and practical addition to any home, offering a sleek, modern look while being highly functional. However, creating a wet room requires careful preparation, especially when it comes to waterproofing and preparing the walls and floors for tiling. In this blog, we’ll walk you through the steps to build wet room walls and floors, ensuring a long-lasting, watertight finish.

We’ll also discuss the importance of proper preparation, the materials you’ll need, and how thin the boards for floors and walls should be to achieve the best results. Additionally, we’ll introduce Strato Aqua Waterproof, a high-performance aqua membrane, and explain its measurements and benefits.

Why Preparation is Key

Before diving into the specifics of wall and floor preparation, it’s crucial to understand why this step is so important. Tile grout and adhesive are water-resistant, not waterproof. Without proper preparation, water can seep through the gaps, leading to leaks, mold, and structural damage. To prevent this, you must create a fully waterproof barrier using materials like backer boards, waterproof membranes, and tanking kits. Additionally, using the right primers and adhesives ensures a strong bond and long-term durability.

Preparing Wet Room Walls

Step 1: Assess the Wall Condition

The first step is to evaluate the existing walls. Depending on the wall type (plasterboard, cement, or another substrate), you’ll need to choose the appropriate materials for waterproofing and tiling. For example:

• Plasterboard walls: These are common but not inherently waterproof. You’ll need to use waterproof materials like green plasterboards or backer boards.

• Cement walls: These are more durable but may still require a waterproof membrane if they’re in poor condition.

Step 2: Choose the Right Wall Material

Here are the most common options for wet room walls:

1. Backer Boards: Cement-based boards like Aquapanel or HardieBacker are ideal for wet rooms. They’re waterproof, durable, and provide a stable surface for tiling.

2. Foam Boards: Lightweight and easy to cut, foam boards like Wedi or Kerdi are excellent for wet rooms. They’re also waterproof and provide insulation.

3. Green Plasterboards: These are moisture-resistant plasterboards, but they’re not fully waterproof. They should be used in conjunction with a waterproof membrane.

4.  Strato Aqua Waterproof Membrane: A premium liquid waterproofing membrane designed for wet rooms, showers, and other high-moisture areas. It’s a two-component, cement-based coating that forms a flexible, durable, and fully waterproof barrier.

How Thin Should Wall Boards Be?

The thickness of wall boards depends on the material and the application:

• Backer Boards: Typically 6mm to 12mm thick. Thinner boards (6mm) are suitable for walls, while thicker boards (12mm) are better for floors.

• Foam Boards: Usually 10mm to 20mm thick. Thinner foam boards (10mm) are ideal for walls, while thicker ones (20mm) provide better insulation for floors.

• Green Plasterboards: Standard thickness is 12.5mm, but they’re not recommended for wet rooms unless combined with a waterproof membrane.

Step 3: Install the Wall Material

• Backer Boards: Cut the boards to size and fix them to the wall using screws and washers. Ensure the joints are tight and seal them with waterproof tape.

• Foam Boards: Apply adhesive to the back of the boards and press them onto the wall. Secure with screws and seal the joints with waterproof tape.

• Green Plasterboards: Fix the boards to the wall as usual, then apply a waterproof membrane like Strato Aqua Waterproof over the entire surface.

Step 4: Tape Joints and Apply Tanking

Once the boards are installed, tape all joints and corners with waterproof tape. Then, apply a tanking kit like Strato Aqua Waterproof over the entire wall surface. This creates an additional layer of protection against water penetration.

Preparing Wet Room Floors

Step 1: Assess the Floor Condition

The type of floor substrate will determine the best preparation method. Common substrates include:

• Concrete floors: These are stable but may require leveling.

• Wooden floors: These need extra reinforcement to prevent movement.

• Old tiles: These should be removed or levelled before installing new materials.

• New anhydrite screed: A popular choice in modern construction, but it requires specific preparation.

Step 2: Choose the Right Floor Material

Here are the most common options for wet room floors:

1. Backer Boards (Aqua Boards): Cement-based boards like Aquapanel are ideal for floors. They’re waterproof and provide a solid base for tiling.

2. Foam Boards: Lightweight and easy to install, foam boards are a good option for floors. They also provide insulation.

3. Decoupling Membrane: This membrane separates the tile layer from the substrate, preventing cracks caused by movement.

How Thin Should Floor Boards Be?

The thickness of floor boards depends on the material and the substrate:

• Backer Boards: Typically 6mm to 12mm thick. For floors, thicker boards (12mm) are recommended to provide a stable base.

• Foam Boards: Usually 10mm to 20mm thick. Thicker foam boards (20mm) are better for floors as they provide insulation and stability.

• Decoupling Membrane: Typically 2mm to 5mm thick. It’s designed to be thin to minimise floor height increase.

Step 3: Install the Floor Material

• Backer Boards: Lay the boards on the floor, ensuring they’re level. Fix them in place using adhesive and screws. Seal the joints with waterproof tape.

• Foam Boards: Apply adhesive to the floor and press the boards into place. Secure with screws and seal the joints.

• Decoupling Membrane: Roll out the membrane over the floor and secure it with adhesive. Ensure there are no air bubbles.

• Waterproof Membrane: Apply Strato Aqua Waterproof evenly over the floor, following the manufacturer’s instructions. Use a roller to ensure full coverage.

Step 4: Prime the Floor

Before tiling, apply a primer to the floor. Priming is essential for porous materials or dusty surfaces, as it improves adhesion and ensures a strong bond. Most manufacturers recommend using a primer, so check the product guidelines.

Advantages and Disadvantages of Materials

Backer Boards (Aqua Boards)

• Advantages: Durable, waterproof, and easy to install.

• Disadvantages: Heavy and may require additional support for wooden floors.

Foam Boards

• Advantages: Lightweight, easy to cut, and provide insulation.

• Disadvantages: More expensive than other options.

Decoupling Membrane

• Advantages: Prevents cracks caused by substrate movement.

• Disadvantages: Adds an extra layer, which may increase floor height.

Waterproof Membrane (Strato Aqua Waterproof)

• Advantages: Provides complete waterproofing, easy to apply, and forms a flexible, durable barrier.

• Disadvantages: Requires careful application to avoid gaps.

Importance of Using the Right Adhesive

When tiling a wet room, it’s essential to use the right adhesive. Standard adhesives are classified as S1 or S2, with S2 being more flexible and suitable for wet rooms. Always choose an adhesive that’s compatible with your tiles and substrate. For more details on adhesive selection, stay tuned for a separate blog.