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External Membrane Type A
Type A waterproofing systems are protective barrier membranes or waterproof coatings that are applied directly to the structure of a building. These systems are designed to prevent the ingress of free water by forming a continuous barrier. Depending on the design and site conditions, the membrane can be applied to either the external (positive side) or internal (negative side) of the structure.
Service information
Type A systems can be applied to either side of a below-ground structure:
- Positive side (external): Common solutions include bonded sheet membranes, sodium bentonite matting, and liquid-applied coatings (cementitious, bitumen, or polymer-based).
- Negative side (internal): Similar systems can be applied to resist water from within the structure, using cementitious coatings or liquid membranes applied by spray, trowel, brush, or roller.
These systems are tailored to suit the construction method, environmental conditions, and performance requirements of each site.
- Residential Developments
- Car Parks
- Light & Heavy Industrial Schemes
- Data Centres
- Sewage Treatments Works
- Refuse Incineration Centers
- Chemical Industry Facilities
- Portable Water Tanks
The Type A waterproofing membranes we work with are designed for high-performance protection against both water ingress and ground contaminants. A laminated geotextile layer provides dual functionality—protecting the membrane during installation and bonding securely to poured concrete for a continuous waterproofing barrier.
Made from advanced HDPE resins, these membranes offer excellent resistance to:
- Ground gases (radon, methane, CO₂)
- VOC’s and hydrocarbons (liquid and vapour)
Pre-applied and fully bonded, they’re ideal for sites with challenging ground conditions requiring durable, long-term waterproofing and gas protection.
Type A waterproofing systems are suitable for a wide variety of below-ground and earth-retaining structures across both residential and commercial sectors, including:
- Residential Developments
- Car Parks
- Light & Heavy Industrial Schemes
- Data Centres
- Sewage Treatment Works
- Refuse Incineration Centres
- Chemical Industry Facilities
- Potable Water Tanks
These systems are especially well-suited to projects where groundwater pressure or contaminated soils pose a risk to the structure’s durability and internal environment.
- Chemical & Gas Resistance: Provides robust protection against ground gases (radon, methane, CO₂), VOCs, and hydrocarbons.
- Long-Term Durability: Guaranteed to perform for the lifetime of the building (60+ years).
- Design Flexibility: Compatible with various construction methods and materials.
- Standards Compliance: Meets all relevant British Standards:
- BS 8102:2009 – Waterproofing
- BS 8485:2015 – Ground gas protection
- C748 – VOC and hydrocarbon resistance
- Cost Efficiency: Early integration avoids future remedial costs and protects internal finishes from damage.
Standard construction details are available for reference and design guidance. However, gas membranes must always be installed by qualified and insured professionals. These membranes perform a critical protective role and are designed to last over 60 years, so they should never be installed based on drawings alone. Always follow the manufacturer’s guidelines and best practices.
Preventive waterproofing means perfection right down to the smallest detail
Concept design
RASCOR’s engineers analyze the waterproofed scheme in terms of structural design, groundwater/gravitational water conditions, and facility size.
Detail design
Full responsibility is assumed for key aspects of design, including the minimum shrinkage reinforcement, joint layout and concreting workmanship.
Site operations
Our engineers provide advice on and actively supervise the incorporation of the RASCOR White Tank waterproof concrete basement system.
Monitoring
Quality assurance is essential to the achievement of the agreed standards of workmanship. These activities are performed continuously up to acceptance/handover and the start of the defects liability period.