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Air Gap Technology

Our range of membranes are manufactured with air gap technology, they consist of a high-density polyethylene (HDPE) sheet, molded into a series of raised studs, or dimples. When the membrane is applied to the substrate the studs create an air gap cavity. This cavity allows the substrate to breathe and any water/water vapour that seeps through the substrate meets the membrane and is drained to a suitable drainage system. This cavity neutralizes the hydrostatic pressure (groundwater pressure), manages and controls the flow of groundwater and also has thermal qualities.

As you can see in the photo below the moisture you can see is the water vapour behind the membrane that has seeped through the substrate, when it makes contact with the membrane and condenses into it’s liquid state it drains down into a drainage system.

Cavity drain membrane with fixing plug

People ask us, “How can something that looks so simple work so well?”

We say, “Looks can be deceptive!” – Behind the success of the DELTA system is the DELTA® Brand of dimpled/studded plastic membranes, and a solid understanding of a complex subject, Dampology – the science of water control.

Water isn’t just a liquid!

The reason so many damp proofing systems fail is because they only target water in its liquid state.  However, water isn’t only a liquid.  It can also be a solid when frozen, or present as a gas (vapour), particles suspended in the air.

To be fully successful, measures to protect below ground structures must take into account the unique characteristics of each of these water forms. The DELTA® range of membranes do precisely that, through Air Gap Technology.

Except in specially engineered systems, in most residential applications Air Gap Technology does not, and is not designed to stop water flow.  Instead, it manages and controls water according to how this substance is known to behave.  Let’s get technical, with a simple explanation of how DELTA® products controls water in each of its three forms.

Ground Water Control:

  • One of the distinctive properties of water is that it is an extremely stable compound (H20) which is virtually impossible to compress in a fixed space in its liquid form. Water molecules always occupy the same amount of space, and water under pressure must always find a way out.  This explains why even tiny cracks in a foundation or small tears in a waterproofing foundation treatment will become a conduit for water in rain-drenched soils. Water will always seek out and force its way into areas of lower pressure.
  • DELTA® products are made of strong, semi-rigid Virgin polyethylene, and installed in such a manner as to form an effective barrier to water.  However, one key to their success is that this dimpled membrane provides a drainage path for any water that does collect. The continuous air gap supplied by this dimpled plastic sheeting represents the path of least resistance, (gravity providing a strong resistance to horizontal or side water flow characteristics), allowing water to flow harmlessly down to the land drainage system at the footings, instead of through the hairline foundation cracks that generally occur as structures shift and adjust over time.

 Frozen Ground Water

  • Why do cracks eventually show up in basements and foundations, even when workmanship is flawless?  The main reason is that the foundation is subject to repeated stress from water in the soil expanding and contracting due to seasonal changes in the moisture content of expansive, moisture sensitive (clay) soils; and freezing of suspended water during winter, which is referred to as adfreezing.   As it warms and liquifies, water can also cause minor settlement in soils around the foundation.
  • DELTA® geo composite products greatly reduce cracking of the foundation due to these processes in two ways.  First, they act as a “slip-sheet” allowing for some movement of the soil around them.  Next, the air gap they provide buffers the foundation against expansion and contraction due to freeze-thaw cycles.

Condensation Control:

  • Water is not only in the soil but in the air around the inside of the foundation or basement.   No water protection system can be completely successful unless it takes this fact into consideration.  As water condenses out of the air, it will do so on the coldest surface.  In most foundations, including those sealed with conventional damp proofing or special plastics on the exterior, the cold surface is on the inside of the foundation wall, since it maintains a temperature close to that of the ground (on average, 55°F) with which it is in contact.  As a result, unless there is constant mechanical ventilation to remove moisture-laden air, such basements are likely to be wet or damp.
  • The key to controlling water here is to protect the foundation from excessive condensation.  DELTA®-MS provides an exterior surface where condensation can form.  The air gap between DELTA®-MS and the foundation ventilates the concrete and acts as a thermal barrier keeping the foundation slightly warmer than the surrounding soil.  Air-borne moisture wicks out of the concrete and is deposited on DELTA®-MS, which is in direct contact with and at the same temperature as the ground.  The condensation that collects on the DELTA®-MS then flows harmlessly down through the air gap to the land drain pipe around the structure.

System features

For any queries on cellar drainage equipment, basement waterproofing solutions or structural waterproofing systems please contact us.

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