Understanding the Drainage Capacity of Membranes
Understanding the drainage capacity of membranes is crucial for effective water management. Membranes help control water flow and prevent flooding by channelling water away from surfaces. They are essential in construction and landscaping projects where proper drainage is needed to maintain structural integrity and prevent water damage.
Membranes have different drainage capacities based on their material, thickness, and structure, such as being dimpled or studded. A general rule (for example) is that a dimple or stud height of 20mm provides better drainage than one of 8mm.
High-density polyethylene (HDPE) is often used for drainage membranes because it is durable and resistant to chemicals and biological attacks and.
Membranes with a geotextile layer filter out debris, preventing clogging and maintaining drainage efficiency.
A membrane’s pressure resistance (compressive load) is crucial, especially in basement waterproofing, where it must support soil, concrete and other materials’ weight.
Drainage membranes are used in various applications:
- Basement Waterproofing
- Subterranean Structure Waterproofing
- For any Earth Retained Structure
- Under Swimming Pool construction
- Green Roofs
- Terraces and Podium Decks
- Blue Roofs
- Hybrid Roofs
- Soakaways and Land drains
- Tunnel and Civil Engineering
Difference between a Type C membrane and an External Drainage membrane
A Type C membrane is used for internal waterproofing, while an external drainage membrane is applied outside structures to manage water and/or protect a Type A primary waterproofing solution and/or protect foundations.
External drainage are geotextile membranes, also called ‘geotextiles’, are protective fabrics used in ground installations for drainage and engineering projects, benefiting both landscaping and construction.
Geotextile membranes are great for separating filtration mechanisms, blocking debris while allowing water flow to prevent flooding. A water-retaining drainage membrane with an integrated geotextile is ideal for flat roofs intended for low-maintenance greenery. The membrane combines filtration, water storage, and drainage.
Drainage Flow
You should be able find the drainage capacity of products like Type C, drainage membranes or external drainage systems in their Technical Datasheets. Check the product catalogue or manufacturer’s website under ‘Technical Information’ or ‘Downloads’.
An 8mm cavity drain membrane with a drainage capacity of 2.25 l/m² can drain 2.25 litres of water per second, per meter. The drainage capacity is often expressed in litres per second (l/s), litres per minute (l/min), or litres per hour (l/h) per meter. For example, a membrane with a drainage capacity of 2.25 l/m² can drain 135 litres per minute (2.25 l/s * 60 seconds) or 8100 litres per hour (2.25 l/s * 3600 seconds) per square meter.
Air Gap
An air gap is the space in a membrane that allows a percentage of litres of air, per square meter. Air gaps are needed in a membrane to create a flow. The flow rate (drainage) is always lower than the air gap.
An 8mm cavity drain membrane with an air gap of 5.3 l/m² has an air gap of 5.3 litres of air per second, per square meter. The air gap is often expressed in litres per second (l/s), litres per minute (l/min), or litres per hour (l/h) per square meter. For example, a membrane with an air capacity of 5.3 l/m² has an airflow of 318 litres per minute (5.3 l/s * 60 seconds) or 19,080 litres per hour (5.3 l/s * 3600 seconds) per square meter.
The air gap in Type C drainage membranes is essential for allowing water to flow efficiently.
Approach scientific claims of membranes with a critical eye to ensure accuracy and reliability.
Delta Technical Team
Delta’s Technical Team offers expert advice and support to find the right membrane for your waterproofing project. We provide comprehensive assistance to meet your specific needs, optimising project performance and cost efficiency. Contact us at 01992 523 523 or info@deltamembranes.com.
