Types of High Quality Drainage Membrane
High quality drainage membrane is an important part of any waterproofing system. It prevents hydrostatic pressure from pushing soil against the concrete foundation.
Sheet drains, also known as dimple membranes, are polypropylene or high-density polyethylene sheets molded with raised knobs or “dimples.” They vary in thickness, flow rates and compressive strength between manufacturers.
Perforated Drain Sheets
Whether used under golf greens, athletic fields or planters, perforated drain sheets are one of the most versatile and durable prefabricated drainage membranes. The dimples act as water retention layers during dry periods, while excess moisture falls through the open perforations and is channeled to drains. In most applications, a geotextile bonded to the drain sheet keeps soil out of the open dimples so they can do their job without clogging.
Often called French drains, these prefabricated drainage systems are designed to prevent excessive groundwater accumulation by redirecting water away from the foundations of residential properties. During heavy rains, these pipes collect and divert water from your yard to avoid flooding or pooling around the basement of your home.
The perforations on these pipes can be oriented up or down to achieve the desired function. Upward-facing perforations limit the collection of slits and debris during drainage collection while downward-facing perforations offer a more dynamic flow. Perforated pipes are durable and resistant to chemicals, moisture, mildew and rot.
The prefabricated MEL-DRAIN TOTAL-DRAIN system combines any regular sheet drain with a high-profile section that allows water to flow to designated drainage exits. This unique feature eliminates the need for select backfill and is quick to install, with a manufactured transition between the sheet drain and high-profile section. Its high-flow design delivers superior in-plane water flow levels, with outstanding clog resistance that is not dependent on backfill material.
Air Gap Membranes
Air gap membranes such as Platon (pictured above) are commonly used in new construction projects to waterproof concrete block walls, permanent wood foundations, High quality drainage membrane existing concrete foundations and Insulated Concrete Forms (ICF). These specialized membranes keep wet soil away from the foundation wall and carry it down the drain path.
Unlike perforated drain sheets, which have their dimples facing the ground and need another product to act as a waterproofing course, air gap membranes can be installed with their dimples facing the basement. This makes them ideal for blindside work and tunnels where gravel isn’t an option, but they can also be used in conventional concrete foundation applications.
The performance of an AGMD device depends on the interaction between the preheated saline feed water and cold permeate water. The water flux across the membrane is determined by the difference in temperature and vapor pressure between the two water streams.
The AGMD process is a versatile water treatment technology with potential to reduce the complexity of textile dyeing wastewater, a complex mixture of salts, surfactants and chemicals. However, it has been difficult to implement in practice because of low water and salt rejection and high energy costs. This paper presents a model for the interaction between the preheated saline and cold water in an AGMD device to assess the effect of temperature, flow rate and the extent of the air gap on the water production rate.
Dimple Membranes
Dimple membranes are one of the most popular drainage solutions for basement walls. Essentially, they prevent groundwater and backfill soil moisture from touching the foundation wall itself. The dimples on the HDPE sheet direct water into perimeter footing drains or into a sump, depending on the severity of the issue. This keeps the concrete foundation dry and allows the basement to be occupied.
This method of directing moisture and groundwater to the drain is also useful for ICF foundations, since it eliminates the need for inches of gravel on the base of the footer. Combined with a fabricated drainage system, it provides the same functionality of full-height gravel at a fraction of the cost.
Peter Barrett, product and marketing manager for Dorken Systems, points out that dimple membranes can be installed much sooner in a construction timeline than spray-on or peel & stick membranes. This is because they don’t require specific temperatures for installation, which is a major time-saver on the ICF block site.
Another benefit of this type of membrane is that it is durable and can be installed by any professional. It is resistant to sagging and tearing, and it can bridge cracks of up to 1/4″ without affecting performance or integrity. Moreover, it is compatible with most fasteners and can be used in conjunction with ICF foam insulation. It is also UV-resistant, and it comes with a vapor barrier to keep water vapor and other gasses, including radon, out of the building envelope.
Geotextile Membranes
The most common type of membrane used in landscaping and civil engineering projects, geotextile fabric (also known as weed mat or garden membrane) is a protective layer that serves three main functions: separation, filtration and reinforcement. It is used to protect the ground and improve drainage and soil stability.
Woven and non-woven geotextile membranes are used in a wide range of situations including separating soil layers, preventing weeds growing and lining drainage systems and soakaway crates as well as land drains. They are also commonly used in equestrian arenas as separators between the sub-base layer and the riding surface.
One of the primary benefits of geotextiles is that they help to separate different soil layers, avoiding mixing. This helps to prevent fine particles and silt from being displaced during rainfall and clogging drainage channels within courser soil. In addition, it stops granular stone composite drainage material layers from sinking into softer subsurface materials which would cause rutting or subsidence over time.
Woven geotextiles are often used in road, railway and embankment construction to stabilise the structure by preventing the granular stone layer from becoming buried beneath softer subsurface material. These woven sheets also have high load capacities, meaning they can withstand a lot of pressure and are ideal for improving the structural integrity of roads or embankments that are built on unstable soils.
