Rising Dampness and Water Pressure

Rising dampness refers to the upward movement of moisture through porous materials such as concrete, mortar, and cementitious substrates as a result of capillary action.

Capillary moisture migration describes the movement of water through interconnected pores and capillaries within porous substrates.

This moisture movement may occur even when there is no visible water leakage, resulting in persistent dampness and deterioration of subsequent coating .

Moisture migration within concrete and cementitious substrates may appear through several visible signs, including:

1. Persistent damp or dark areas.
2. Efflorescence and salt deposits.
3. Blistering or peeling of coatings.
4. Loss of adhesion between finishes and the substrate.
5. Deterioration of plaster and cementitious finishes.
6. Discoloration and surface deterioration.
7. Recurring dampness after repainting or surface treatment.

These symptoms indicate the need to assess the substrate and identify the moisture source before applying a new waterproofing or finishing system.

Understanding the direction of water pressure is an important factor when selecting a waterproofing system.

Positive Water Pressure is water pressure acting in a direction that generally pushes the waterproofing layer toward the substrate.

Negative Water Pressure is water pressure acting from behind the waterproofing layer, generally tending to push the membrane away from the substrate.

Negative water pressure may occur on different concrete and cementitious surfaces where water or moisture develops within or behind the substrate.

Therefore, waterproofing systems exposed to negative water pressure should provide adequate adhesion to the substrate and sufficient resistance to water pressure to minimize the risk of blistering, debonding, or loss of adhesion.

For concrete and cementitious substrates affected by moisture or water pressure, a flexible polymer-modified cementitious waterproofing system designed to resist both positive and negative water pressure can provide an effective solution, when compatible with the substrate and project conditions.

Uniguard 2K Plus is a two-component, flexible, polymer-modified cementitious waterproofing membrane designed for applications where resistance to water penetration is required. It can be applied to damp substrates and provides resistance to salts, making it suitable for applications involving rising dampness.

The system provides resistance to:

1. Positive water pressure up to 7 bar.
2. Negative water pressure up to 5 bar.

Hydrostatic pressure testing has also demonstrated no water penetration within the specified test conditions.

The system also provides good adhesion to various substrates, including concrete, cement mortar, stone, and masonry, and offers the ability to bridge hairline cracks.

The ability to apply a waterproofing system to damp substrates can be particularly important when complete drying of the substrate is difficult to achieve.

According to the product TDS, Uniguard 2K Plus can be applied to damp substrates, provided that the substrate is properly prepared and free from contaminants or materials that could affect adhesion.

The system is also described as water-vapor permeable, which allows water vapor to pass through the membrane rather than forming a complete vapor barrier.

Even when using a waterproofing system designed for damp conditions and water pressure, proper substrate preparation remains essential for long-term performance.

The substrate should be sound, clean, and free from dust, oils, grease, loose materials, and other contaminants. Depending on the substrate condition, suitable preparation methods may include abrasive blasting, high-pressure water cleaning, wire brushing, or grinding.

For Uniguard 2K Plus, the system is recommended to be applied in two to three coats to achieve a total thickness of 3 mm, in accordance with the product TDS.

Joints, connections, penetrations, corners, and other critical details should also be properly treated to maintain the continuity of the waterproofing system and minimize potential water pathways.

Flexible cementitious waterproofing systems designed to resist positive and negative water pressure can be used in a range of concrete and cementitious applications, including:

1. Basements and underground structures.
2. Retaining walls.
3. Water tanks.
4. Swimming pools.
5. Bathrooms and wet areas.
6. Concrete surfaces exposed to moisture.
7. Internal waterproofing of walls and floors exposed to negative water pressure.

These applications include internal waterproofing of basement walls and floors, where negative water pressure may be present.

Water exposure conditions can vary depending on the location and construction of the structure. In some applications, the waterproofing system may be exposed to positive water pressure, while in others it may be subjected to negative water pressure.

Therefore, selecting a waterproofing system capable of resisting both positive and negative water pressure provides greater flexibility for applications where water movement and pressure conditions may vary.

Rising dampness and capillary moisture migration can affect the performance and durability of concrete, cementitious substrates, and finishing systems. Understanding the source and movement of moisture, together with the direction of water pressure, is essential for selecting the appropriate waterproofing solution.

A flexible polymer-modified cementitious waterproofing system capable of resisting both positive and negative water pressure can provide an effective solution for moisture-affected substrates when correctly selected and applied