Why should I tank my bathroom?

Bathroom tanking is one of the most important steps in achieving a long-lasting tiled installation. Although tiles and grout are often assumed to be waterproof, they are not designed to act as a complete barrier against moisture. Water can pass through grout joints, movement points and service penetrations, particularly in areas that are used daily.

Without a waterproof layer beneath the tiles, moisture can soak into walls and floors, gradually causing damp, mould and structural damage. Tanking prevents this by forming a continuous waterproof membrane behind the tiled surface, protecting both the substrate and the building itself.

Tanking works by creating a sealed layer between the tiles and the surface beneath. Even if moisture reaches the back of the tile, the membrane stops it from penetrating plasterboard, cement boards, screeds or timber. This is especially important in showers, wet rooms and around baths, where repeated exposure to water is unavoidable.

A properly installed tanking system remains flexible, allowing it to cope with small amounts of movement without cracking or failing.

Relying on tiles and grout alone leaves installations vulnerable. Grout is naturally porous and movement at corners or junctions can create fine gaps over time. Water entering these areas can weaken tile adhesives, loosen tiles and damage the background surface long before there are any visible signs on the face of the tiles.

This is why tanking is considered standard practice by professional installers in wet areas.

In a bathroom, tanking should be applied wherever water is likely to come into regular contact with the surface. This typically includes shower enclosures, wet room floors and surrounding walls and bath splash zones. Particular care should be taken at high-risk points such as:

• Wall-to-floor junctions
• Internal and external corners
• Pipe penetrations and shower valves
• Drainage areas

Even in a conventional bathroom rather than a full wet room, waterproofing these areas significantly reduces the risk of future problems.

Our waterproofing and tanking range is designed to provide dependable protection beneath tiled surfaces. Liquid waterproofing membranes are easy to apply with a brush or roller and are ideal for working into corners, joints and awkward details. Once cured, they form a seamless waterproof layer ready to receive tiles.

To strengthen the system, waterproofing tapes and pre-formed corner pieces are used to reinforce joints and changes in plane. These areas are most prone to movement and reinforcing them helps maintain the integrity of the waterproof layer over time. Using compatible products from the same range ensures consistent performance and avoids the risks associated with mixing systems.

For example, a complete system might use the Mapei Mapelastic Aquadefense Tanking Kit, combining a rapid‑drying liquid membrane with waterproof tape for bathrooms, wet rooms, and showers. Critical joints and corners can be reinforced with Mapeband Easy Flexible Sealing Tape, both embedded into the membrane for added flexibility and durability. Mapeguard ST Waterproofing Sealing Tape can be used where a narrower tape is needed. 

Good preparation is essential for effective tanking. Surfaces should be clean, dry and structurally sound before waterproofing begins. Joints and corners should be reinforced first, followed by an even application of the membrane at the recommended coverage. Adequate drying time must be allowed before tiling and flexible adhesives and grouts should always be used in wet areas to accommodate movement. 

Tanking a bathroom or shower is not an optional extra; it is a fundamental part of modern tiling practice. Water damage often develops slowly and out of sight, but the cost and disruption of repairs can be significant once it becomes apparent

By using Solseal’s waterproofing and tanking products, you create a reliable barrier beneath the tiles that protects the structure, supports the tiled finish and helps ensure your bathroom or shower remains watertight for years to come.