Technical solutions for waterproofing and radon protection.

Carlo Pesta, Engineer – Volteco Technical Representative

Project Context

We are located in the Casoretto neighborhood of Milan, bordered by the Naviglio della Martesana Canal, the Central Station, and Leoncavallo Street. Officially established two years ago, it has undergone a major redevelopment, becoming a growing cultural and residential hub.

A new residential complex was built in this area as part of a project to demolish an existing building and construct a new one. The structure includes an apartment building above, with a garage and utility rooms distributed across a basement level.

The construction presented geotechnical and structural challenges that required advanced solutions in terms of waterproofing and radon protection management, as required by the current regulations of the Lombardy region.

Geotechnical Challenges and Solutions Adopted

1. Radon Gas Ground Depressurization

Radon gas, being a naturally occurring element in the subsoil, poses a significant risk to underground spaces, as it can accumulate in enclosed spaces and reach concentrations dangerous to health. Its presence is particularly critical in structures with underground floors. In some contexts, its concentration in indoor environments can be significant even at ground level. Creating underground volumes can significantly exacerbate the problem, as a void in the ground can create a significant depression that naturally attracts great quantities of gas.

To manage it, a passive ground depressurization system was implemented following the guidelines of Regional Law 12678 using:

• A network of micro-perforated pipes with a double ring distribution, positioned in the ground at the level below the lean concrete foundation of the garage, one ring adjacent to the perimeter near the micropile foundation, and an inner ring near the elevator shaft.
• Vertical evacuation points that convey, through watertight pipes, the gas captured by the depressurization system from the elevator shaft area to the building roof, where it is released into the atmosphere.

2. Treatment of the crown beam with structural interference

To meet the specific design and construction site requirements and avoid any bypassing of the waterproofing systems, the request was to connect the basement waterproofing to the roof waterproofing, avoiding interference at the structural connection between the roof slab and the crown beam.

For this reason, it was decided to treat the crown beam in the pre-cast phase, managing the interference caused by the crossing of the Berlin wall micropiles. This made it possible to create a connection with the roof waterproofing on the external perimeter, avoiding interference with the structure.

Volteco Solutions

To allow the micropiles to pass through the crown beam, avoiding interference with the waterproofing system, a specific solution was adopted:

• Individual sealing of the micropiles: each micropile was sealed using Akti-vo 201 and hydro-swellable waterstop WT 102, applied to the outer circumference of the base at the point where it penetrated the waterproofing layer.
• The micropile head was hollowed out by 5 cm, sealed on the inner perimeter of the micropile with Akti-vo 201, and filled with pourable waterproof grout Bi Mortar Levelling Seal, ensuring the continuity of the waterproofing.

To ensure effective protection from pressurized water, the hydro-reactive Amphibia 3000 Grip membrane was used, an advanced solution that ensures active and long-lasting waterproofing.

The project involved applying the membrane to the following structural elements:

• Foundation: Amphibia 3000 Grip was used for the foundation slab, providing a complete water barrier and preventing moisture migration from the subsoil.
• Walls against temporary structures: Amphibia 3000 Grip, characterized by high adhesion to the substrate, offers continuous protection against water infiltration and humidity, reducing the risk of deterioration over time.

Technology and Performance

The Amphibia 3000 Grip membrane stands out for its self-reaction in the presence of water, forming a hermetic seal that prevents the ingress of water and moisture. Furthermore:

• It self-seals in the event of accidental perforations, ensuring continuous protection.
• It resists hydrostatic variations, adapting to soil conditions without losing effectiveness.
• It offers a complete and continuous solution, eliminating the risk of discontinuity between joints and fittings.

The use of this technology has allowed us to create a reliable waterproofing system, essential for protecting underground spaces and ensuring the durability of the entire building.

Procedure Execution

The project was carried out by a specialized waterproofing contractor. The work required high precision, particularly for the treatment of the micropiles and the installation of the membranes, with constant monitoring of quality and watertightness.

Conclusion

The integration of structural design, advanced waterproofing systems, and radon gas management solutions has enabled the construction of a project that complies with the safety and durability standards required for residential buildings with basement levels. The Casoretto Re-development Project is an example of the application of innovative techniques for the protection and healthiness of underground structures.