Waterproof tanking

Cistern roofs, also known as blue roofs, store and manage rainwater in buildings. They are widely used on green roofs and enhance a building’s insulation and energy efficiency.

These structures draw inspiration from ancient cisterns—large, typically underground reservoirs that stored water for human consumption or other uses.

The importance of properly waterproofing cisterns

Traditional cisterns must be completely watertight to ensure the water retains the properties that make it suitable for human consumption. However, since these tanks are typically buried, ground movement can cause cracks and leaks. In turn, the passage of time can lead to wear, erosion, and moisture.

Similarly, a blue roof—even if newly constructed—will lose its watertightness if not properly waterproofed. This will lead to issues with energy efficiency, maintenance, and potential structural damage to the building.

Whether it’s a new construction or a renovation project, using a suitable waterproof tanking system for water tanks is crucial to ensure high-quality water and prevent structural damage.

Applying a liquid waterproofing membrane is key to ensuring that cisterns and potable water tanks maintain their watertightness. In this case, the waterproofing system must also be suitable for potable water. Therefore, UltraFlex PW, a liquid waterproofing membrane, is the most appropriate waterproofing solution for cisterns and tanks in these applications.

Advantages of waterproof tanking for cisterns and tanks

For its part, the use of the UltraFlex PW liquid waterproofing membrane is an effective solution because:

It does not require prior priming.
It adapts to various perimeters.
It fully adheres to the surface, eliminating the need for joints.
It eliminates waiting times during application.
It enables the waterproofing of drains.

How to waterproof cisterns and water tanks step by step

Before applying the waterproofing agent for cisterns, it’s important to know the steps to follow.

Clean the tank or cistern

It is crucial that the surface is free of dirt, mold, or contaminating particles. In addition, it must be dry and firm. Through thorough cleaning, we also ensure that the space is disinfected and suitable for storing water intended for human use.

Apply the first coat

At this point, it is important to thoroughly mix the tank waterproofing compound and apply it directly to the surface using a roller, preferably with the wet-on-wet system, to achieve a thickness of 1.5–2 mm (equivalent to a consumption of approximately 2 kg/m²). The waterproofing compound for cisterns and tanks should be applied at temperatures between 2 °C and 35 °C. For vertical surfaces, the Tixal additive can be used to prevent the liquid membrane from sagging.

Install the reinforcement mesh

Here, with the first coat still wet, the reinforcing mesh is applied. It’s important to ensure it’s well impregnated and lies flat.

Apply the second coat

Immediately afterward, the second coat of UltraFlex PW should be applied over the mesh. It is important to ensure that there are no visible holes.

Related applications and keywords: tanking waterproofing systems, waterproof tanking membrane and waterproof tanking paint.

Projects executed with:

UltraFlex PW

A liquid waterproofing membrane suitable for permanent contact with water intended for human consumption. Once catalyzed, it forms a continuous, elastic membrane without joints or overlaps.

Ideal for waterproofing reservoirs, tanks, channels, and other potable water containment systems constructed of concrete and protected from sunlight.

Waterproof tanking