What is the difference between a damp proof membrane and a vapour barrier?

Knowing which solution is right for the application or problem you face means understanding the difference between a damp proof membrane and a vapour barrier.

While damp proof membranes are used under floors to stop damp rising up into the building, vapour control membranes prevent moisture from inside the building creeping into the walls and accumulating in the insulation cavities. Vapour control membranes are typically lighter and thinner than damp proof membranes and, while it is also possible to use a damp proof membrane in walls, they are more generally used to prevent water ingress and therefore often used beneath concrete floors or slabs.

How to Use a Damp Proofing Membrane

When it comes to damp proofing, there is a choice to be made between a liquid solution or a sheet membrane. Liquid damp proofing offers a less invasive but more time-consuming option, with some needing more than one coat and all requiring substantial drying time. It can also be difficult to achieve the correct layer thickness and to achieve an even finish over the entire surface.

Sheet membranes are easy to use, coming in a variety of sizes, and can be laid straight on to the sub-surface, with no delay before laying the flooring on top. DPM sheets are also very quick and convenient when covering large areas and the overlap (of around 150mm) can be secured using specially designed double-sided tape.

How to Use a Vapour Control Membrane

Water getting in is only half the story, particularly in modern buildings where water vapour can’t escape as easily as it can in older ones. Here, vapour control membranes are needed to prevent water accumulating in wall cavities, having evaporated inside the building where it’s warm and then cooled down inside the walls as it hits the colder air from outside. Preventing this water accumulation is particularly important in timber-framed structures where the water can cause serious damage to the wood.

For more advice on how you can use either Siteworx Damp Proof Membrane or Siteworx Vapour Control Membrane to prevent damp getting where it shouldn’t be, contact the friendly team at Growtivation for advice on 0800 197 8885 or email sales@growtivation.com.

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