Everything You Need To Know About Internal Damp Proofing: Types, Fitting, Cost And Prevention

Damp proofing is essential for maintaining building safety and stability. It centres around methods to prevent moisture from penetrating a property's interior walls and floors. When moisture makes its way into these areas, it can not only spoil a space's appearance but also lead to significant damage over time.

With internal damp proofing, the aim is to protect the structure against potential damage. It's a key measure in averting structural issues, health concerns from mould and mildew, and costly repairs that might result from uncontrolled moisture.

This guide will explore internal damp proofing in depth. It will also cover the various types available, the fitting process, the costs involved, and strategies for moisture prevention. The aim is to provide you with the necessary information to ensure a dry and healthy environment in your home or commercial building.

Internal damp proofing, damp-proof membranes, waterproof plasters, dehumidifiers

What Is Internal Damp Proofing?

Internal damp proofing is a method used to protect building interiors from moisture. This process involves measures taken within a structure to prevent dampness from penetrating internal walls and floors, ensuring a dry, healthy living environment by mitigating potential moisture-related issues.

Why Would You Need Internal Damp Proofing?

Internal damp proofing is essential for safeguarding the integrity of your property and maintaining a healthy indoor atmosphere.

When excess moisture finds its way into your home, it can cause a host of problems—from damaging plaster and paint to fostering the growth of mould and mildew—which can have detrimental effects on health.

By implementing internal damp proofing measures, you help preserve the structure of your building, prevent the decay of building materials, and create a more comfortable and safer living environment.

What Are the Types of Internal Damp Proofing?

Internal damp proofing can come in various forms, each designed to tackle moisture build-up within your home in different ways. From barriers that block damp to systems that manage and remove it, these solutions work to keep your indoors dry and protect your property from potential water damage.

Damp-Proof Membranes

Damp-proof membranes are sheets of waterproof material installed on walls or floors to block moisture.


  • Effective moisture barrier
  • Can be applied to existing structures


  • Can be costly to install
  • Requires professional fitting

Waterproof Renders or Plasters

Waterproof renders or plasters act as a protective coat over internal surfaces to keep out moisture.


  • Provides a smooth finish
  • Protects against surface damp


  • Not effective for all damp issues
  • Skill required for application

Cavity Drain Systems

They manage water ingress by directing it away from interior spaces into a drainage point.


  • Non-invasive installation
  • Easy to maintain


  • Initial setup can be complex
  • Requires ongoing maintenance


Dehumidifiers pull moisture from the air, reducing indoor dampness and condensation. Although they’re a convenient solution, their costs quickly add up.


  • Portable and user-friendly
  • Immediate effect on air quality


  • Running costs can add up
  • Not a permanent solution

Vapour Barriers

Vapour barriers are materials designed to prevent moisture-laden air from condensing within building structures.


  • Minimises risk of condensation
  • Can be installed in new builds and renovations


  • Incorrect installation can lead to issues
  • Not suitable for all building types

Improved Ventilation

Improved ventilation helps to reduce indoor humidity levels and control moisture.


  • Reduces potential for mould growth
  • Helps to improve air quality


  • May not be sufficient alone
  • Can lead to heat loss

Anti-Mould Treatments

Anti-mould treatments involve applying chemicals to surfaces to prevent mould growth.


  • Directly targets mould spores
  • Easy to apply


  • Chemicals may be hazardous
  • Not a long-term solution without addressing underlying dampness

Repairs and Maintenance

Repairs and maintenance include fixing leaks and cracks to prevent water entry.


  • Addresses the root cause of damp
  • Can prevent future issues


  • Can be time-consuming
  • May require ongoing attention

How Do You Fit Damp Proofing?

  1. Evaluate the Damp First: Identify the source and type of dampness to tailor the most effective solution. It's critical to understand whether the damp is rising, penetrating, or caused by condensation to choose the right damp proofing method.
  2. Choose the Correct Method: Select a damp proofing type that suits the identified problem and your property's needs. Depending on the evaluation, options range from installing a damp-proof membrane to improving ventilation or using dehumidifiers.
  3. Prepare the Area: Clear the space where the damp proofing will take place, ensuring surfaces are ready. This might involve removing plaster, wall coverings, or floor finishes to apply the chosen damp proofing method directly to the problem area.
  4. Install the Damp Proofing: Carefully fit the chosen damp proofing measure, following manufacturer guidelines for best results. Whether it's applying membrane, rendering, or installing a cavity drain system, proper installation is crucial for lasting effectiveness.
  5. Replaster and Refinish: After installation, walls and floors should be replastered and refinished as necessary. This step completes the damp proofing process, leaving surfaces not only protected but also visually appealing and ready for redecoration if desired.
  6. Ongoing Maintenance: Regular checks and maintenance ensure the damp proofing continues to perform effectively. Post-installation, it's important to maintain the area to prevent new damp issues from arising, which includes checking for any potential leaks or damage.
Internal damp proofing, damp-proof membranes, waterproof plasters, dehumidifiers

Can You DIY Internal Damp Proofing Or Do You Need A Pro?

Yes, you can DIY internal damp proofing for some simple tasks, but professional help is often recommended.

Homeowners can perform simple tasks like improving ventilation, using dehumidifiers, and applying anti-mould treatments. However, when it comes to installing damp-proof membranes, waterproof plasters, or cavity drain systems, the expertise of a professional is invaluable.

These methods require technical knowledge, skill, and, in some cases, specialist tools to ensure they are fitted correctly and effectively. Incorrect installation can lead to further damage and costs. It’s therefore advisable to hire a professional for complex issues.

How Long Does Internal Damp Proofing Last?

The lifespan of internal damp proofing can vary. For example, a well-installed damp-proof membrane could last for decades, while other methods, like dehumidifiers offer more temporary solutions and require ongoing maintenance or replacement. Regular checks and upkeep are essential to ensure long-term efficacy.

How Much Does Internal Damp Proofing Cost?

Internal damp proofing can cost anywhere from a few hundred pounds for simple DIY solutions to several thousands for professional installation of complex systems. Prices vary widely based on the size of the area, type of damp proofing method chosen, and the extent of the damp issue.

  • DIY treatments, such as anti-mould paints and sealants, may cost between £20 to £150, depending on the quality and quantity needed.
  • Dehumidifiers range from £50 for a basic model to £500 for advanced units with additional features.
  • Improved ventilation through installing vents or fans can cost between £150 to £500.
  • Damp-proof membranes and waterproof renders or plasters typically require professional fitting, which can cost from £70 to £150 per square metre.
  • Cavity drain systems, which are often part of more extensive damp proofing projects, can start from £2,000, including installation.

Professional services may also include an initial survey fee, varying from £100 to £500, which may be waived if you proceed with the recommended treatments.

Cost fluctuations depend on the severity of the damp, property size, and location, as well as the accessibility of the area to be treated.

How Do You Get Internal Damp?

Internal damp typically occurs when moisture from the outside gets into the walls or floors of a building.

This can happen through a range of ways, such as penetrating damp caused by leaky pipes, faulty guttering, or rain seeping through because of damaged roofing or masonry. Meanwhile, rising damp arises when water from the ground soaks up into the bricks and mortar of a building due to a damaged or non-existent damp-proof course.

Moreover, condensation contributes to internal damp and is often the result of poor ventilation and heating fluctuations, which causes water to collect on cold surfaces within a building.

Regular property maintenance and awareness of the signs of damp can help in early detection and prevention.

Does Internal Damp Proofing Prevent Mould?

Yes, internal damp proofing can prevent mould by creating barriers that stop moisture from entering internal spaces where mould could grow. Effective damp proofing reduces the dampness within walls and floors, which, in turn, lowers the likelihood of mould developing.

Mould thrives in moist environments, so by controlling the internal climate and reducing humidity through various damp proofing methods, you significantly reduce the risk of mould.

It’s important to note that damp proofing should be part of a broader strategy to prevent mould, which includes good ventilation and consistent property maintenance.

Bottom Line

Internal damp proofing is a critical step towards maintaining a structurally sound and healthy home environment.

As we discussed initially, the problems associated with internal dampness range from structural damage to health concerns, making it vital to address any issues swiftly and effectively. Now that you understand the types of internal damp proofing available, the fitting process, costs, and preventive measures, it's time to take action.

Protect your home and your health by getting in touch with Watertight Homes for tailored advice and services. A damp-free home not only ensures a solid foundation for your property but also a comfortable living space for you and your loved ones.

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