A damp proof membrane used for damp proofing

What Is A Damp Proof Membrane?

Key Takeaways

Definition of Damp-Proof Membrane (DPM): A damp-proof membrane (DPM) is a crucial component of damp-proofing strategies, acting as a physical barrier to prevent moisture ingress into buildings.

Materials and Effectiveness: DPMs are constructed from materials such as polyethene, polypropylene, or asphalt, providing effective protection against rising damp, condensation, and groundwater ingress through walls and floors.

Functions and Importance: DPMs prevent various moisture-related issues, including visible wet manifestations, salt degradation, rot, and mold growth. Commonly installed beneath concrete floors, DPMs contribute significantly to the overall protection of a property.


A damp-proof membrane is one of the most essential parts of the damp-proofing strategy. As the name goes, a damp-proof membrane is like a physical barrier that protects the properties against moisture ingress.

DPMs are made up of various materials such as polyethene, polypropylene, or asphalt, which are pretty effective against dampness that rises through walls and floors, therefore protecting against rising damp, condensation, and groundwater ingress through damp walls.

To be honest, damp-proof membranes are pretty effective and are able to create a continuous barrier that stops any kind of moisture from entering the house. And that’s not it – there’s a lot more that makes them so unique and a staple in the damp proofing strategy, which we will talk about further. So, let’s get started with damp proofing membranes then.


Dampness on ceiling which caused brick exposure

What exactly is a Damp-Proof Membrane (DPM)?

A damp-proof membrane, often known as a DPM, is a material designed to prevent moisture from infiltrating a structure’s internal walls and floors. Its efficacy extends to minimizing a variety of moisture-related issues, including visible wet manifestations on concrete floor and surfaces, salt degradation, the development of rot, and mould growth.

This critical barrier is commonly used beneath concrete floors, acting as an efficient barrier and deterrent against moisture intrusion. It is one of the most trustworthy damp-proofing options, considerably adding to the fortification of your property’s preventive measures.

Structures are vulnerable to the damaging effects of penetrating damp, rising damp, and condensation in the absence of a properly installed damp-proof barrier, particularly on freezing surfaces existing concrete floors. If these faults are not addressed swiftly and effectively, they might cause structural damage to the structure over time.


Complete destruction of a store room due to dampness

How Does a Damp-Proof Membrane (DPM) Work?

Damp-proof membranes made of impermeable plastic materials provide a substantial barrier against moisture intrusion.

The membrane’s surface carefully adopts a stud pattern, intelligently creating an interstitial air gap that permits progressive evaporation of water while guaranteeing the nearby wall structure’s unrestricted integrity.

Precision and care are required throughout the installation procedure to avoid potential weaknesses such as rips or holes in the plastic membrane sheet.

Such structural flaws might jeopardize the damp proofing’s impermeability, allowing moisture to infiltrate the damp concrete. The repercussions of such violations would undoubtedly result in a severe reduction in the overall effectiveness of the damp protection system.

The need for strict adherence to established standards is highlighted, particularly in accordance with the criteria defined by British Standards.

A key factor within governmental construction requirements pushes for the use of polyethene sheets with a gauge of 1200. This strict compliance with regulatory rules is critical in avoiding any future issues and costly consequences related to water intrusion.

By choosing a substandard polyethene sheet and insulation materials over the required construction norms, a concrete risk of weakening the structural resilience of the property is introduced. That, in turn, may allow water to infiltrate, setting the stage for significant structural and financial consequences down the road.


Black mould stains on a wall

How is a Damp-Proof Membrane Installed?

One of the most compelling reasons to prefer the use of a damp-proof membrane is its ease of installation and inherent flexibility. The second characteristic, indicating the ability to adapt to structural alterations, gives it a longer lifespan and reduces the likelihood of operational faults.

The following is the procedure used by a damp-proofing professional in the installation of such a membrane:

  • Before the procedure can begin, the surveyor must conduct a thorough evaluation and resolution of the detected damp issue.
  • Following that, the plaster is carefully removed from the selected wall, and the original brickwork is restored correctly.
  • The damp-proof membrane is then painstakingly designed to fit the exact measurements of the wall.
  • The membrane is then carefully applied to the wall, with meticulous attention to detail.
  • The damp-proof membrane is exposed to drilling in a scientific manner, assuring its firm and solid location.
  • Finally, specialist membrane fixed plugs are wisely integrated into the entire installation, providing the dual aim of strengthening the plastic membrane in its intended area and preventing any unintentional permeability of the membrane.

Peeling of plaster work due to dampness


What if You Do Not Get a Damp-Proof Membrane (DPM) Installed?

If a damp-proof membrane is not installed, you may face three types of dampness: lateral dampness from walls and ceilings, rising dampness from the ground, and condensation due to excessive moisture and poor ventilation. Not using a full damp proof membrane installation can lead to various problems such as:

  1. Wooden skirting may break and become weak.
  2. Noticeable damp patches may appear.
  3. Molds can grow in certain areas.
  4. Wood may rot, potentially affecting structural integrity.
  5. Furniture and wallpaper may suffer damage.


Is a damp proof membrane necessary?

A damp proof membrane (DPM) is crucial in construction to stop moisture from entering buildings through the ground. It acts as a barrier against rising damp, safeguarding walls and floors from water. Without a DPM, moisture can cause problems like mold, decay, and structural damage, making it vital for a dry and healthy indoor environment.

Is damp proof membrane just plastic?

Plastic is commonly used for damp proof membranes, but alternatives like polyethylene, bitumen, rubber, and synthetic compounds are available. The material choice depends on factors like the application, building regulations, and desired protection level. Modern membranes often use multiple layers of different materials for increased durability and better moisture prevention.

What is the difference between damp proof course and damp proof membrane?

“Damp proof course” (DPC) and “damp proof membrane” (DPM) are related terms but have different uses. A damp proof course is a barrier in building walls, above ground, to stop rising damp, made of materials like slate or plastic. In contrast, a damp proof membrane, typically plastic or synthetic, acts as a barrier under concrete floors or within walls to prevent ground moisture from affecting the structure. Both prevent moisture, but they are used in different parts of a building.

How long does damp proof membrane last?

A damp proof membrane’s lifespan relies on material quality, installation, and environmental factors. A good one can last decades, but wear, construction damage, and maintenance affect longevity. Regular checks and prompt issue resolution help maintain its effectiveness in preventing moisture.

Table of Contents

Picture of Sam Fitzgerald – CSRT Damp Surveyor

Sam Fitzgerald – CSRT Damp Surveyor

Author – CSRT Damp Surveyor
Sam is a highly qualified and seasoned damp surveyor with over ten years of specialised experience. With a strong academic foundation in building surveying and numerous professional certifications, Sam has established himself as an authority in the field of damp diagnosis and remediation.

At Damp Surveyors Ltd, Sam applies his extensive knowledge to help homeowners across the UK address and solve their damp issues effectively. His approach combines cutting-edge techniques with a commitment to honest, client-focused service, ensuring that every survey and recommendation is tailored to the specific needs of the property.

As a thought leader, Sam’s insights into damp prevention and treatment have been featured in industry publications, underscoring his role as a trusted expert dedicated to maintaining the integrity and comfort of your home.

Testing device for measuring dampness in a house


At Damp Surveyors Ltd, we stand out as your premier choice for damp survey services in the UK. Our commitment to excellence and customer satisfaction sets us apart. Here’s why you should choose us:

  • Exclusive 3 Free Quotes: We offer a one-of-a-kind optional service where you not only get our top-notch damp survey but also receive 3 free quotes from vetted local companies, giving you peace of mind by saving you thousands on getting the most competitive quotes, and also time researching and contacting other reputable companies.
  • Knowledge and Experience: We provide unmatched knowledge to every survey we conduct thanks to our team of seasoned professionals and years of industry experience. This guarantees accurate assessments and practical solutions.
  • Nationwide Coverage: Whether you’re in a bustling city or a rural area, our services extend across the UK, making us accessible wherever your property is located. Choose us for nationwide reliability and excellence.

Choose Damp Surveyors Ltd as your reliable partner for all-inclusive survey needs. Our top concerns are the health and safety of your property, and we are committed to providing outcomes you can trust.

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