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How to Tank a Basement

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Basement tanking, a term more familiar in the UK, refers to the methods used to waterproof basements or below-ground structures. Essentially, it involves creating a barrier that prevents water from entering the space. This process is vital, especially in areas prone to dampness or flooding. The essence of basement tanking lies in its approach, which can vary from applying waterproof membranes to installing drainage systems or using water-resistant coatings.

Planning and Preparation for Basement Tanking

Before embarking on the task of basement tanking, careful planning and preparation are essential to ensure a successful outcome. This process involves assessing your basement’s specific needs, identifying potential sources of water ingress, evaluating any existing damage, choosing the optimal time for the project, and gathering the necessary tools and materials.

Assessing Your Basement’s Needs

The first step in planning for basement tanking is to understand the unique requirements of your space. Consider factors such as:

  • Usage of the Basement: The intended use of the basement, be it storage, living space, or utility area, can dictate the type of waterproofing needed.
  • Basement Size and Layout: Larger basements or those with complex layouts may require more comprehensive tanking solutions.
  • Existing Ventilation Systems: Adequate ventilation plays a key role in maintaining a dry basement post-tanking.

Identifying Potential Water Sources

Identifying where water might be entering your basement is critical. Common sources include:

  • Groundwater: Especially in areas with a high water table.
  • Surface Water: Rainwater or melting snow infiltrating through walls or the floor.
  • Internal Sources: Such as leaks from plumbing or appliances.

Evaluating Existing Damage

Inspect your basement for signs of existing damage, which may include:

  • Cracks in Walls or Floor: These can be entry points for water.
  • Mould and Mildew: Indicators of ongoing moisture issues.
  • Efflorescence: White, powdery residue on walls, a sign of water seepage.

Choosing the Right Time for Tanking

Timing is crucial for basement tanking. Ideally, undertake this project:

  • During Dry Weather: Tanking during a dry spell allows for better setting and curing of waterproofing materials.
  • Outside of Winter Months: Cold temperatures can affect the application and effectiveness of certain tanking products.

Types of Basement Tanking

Basement tanking comes in various forms, each with its specific applications, advantages, and limitations. Understanding the differences between internal and external tanking, as well as familiarising yourself with the common tanking methods – cementitious, membrane, and cavity drain systems – is crucial in selecting the most suitable approach for your basement.

Internal Tanking:


  • Easier and less invasive to install, especially in existing buildings.
  • Ideal for retrofit projects where external access is limited.
  • Protects the interior space directly.


  • Puts pressure on the internal structure.
  • Limited in its ability to handle severe water ingress.
External Tanking:


  • Addresses water ingress at the source.
  • Protects the external walls and structure of the building.
  • Generally more effective for preventing water penetration.


More labour-intensive and costly.

Requires excavation around the building, which is not always feasible.

Keep Your Home Looking Like New For Years To Come

Tanking Methods: Cementitious, Membrane, and Cavity Drain Systems

Cementitious Systems:

Made from a mix of cement and water-proofer, these coatings are applied directly to walls and floors. 

Pros: Strong and durable, offering a seamless barrier.

Cons: Less flexible, can be prone to cracking if the structure shifts.

Membrane Systems:

Involves applying a waterproof membrane to walls and floors.

Pros: Offers flexibility, accommodates slight movements in the structure.

Cons: Requires an air gap or drainage system to manage water that gets behind the membrane.

Cavity Drain Systems:

Uses a studded membrane to channel water into a drainage system.

Pros: Effective in managing high water levels, and allows walls to ‘breathe’.

Cons: More complex to install and requires ongoing maintenance.

Additional Considerations for Basement Tanking

Once you’ve completed the tanking process, there are additional factors to consider to ensure your basement remains a safe, comfortable, and functional space. These include managing ventilation and humidity, choosing suitable insulation, addressing electrical and plumbing needs, and understanding the legal and safety aspects of basement tanking in the UK.

Ventilation and Humidity Control in Tanked Basements

Maintaining Air Quality: Proper ventilation is crucial in preventing the build-up of damp and musty air. Consider installing mechanical ventilation or air bricks to promote airflow.

Controlling Humidity: Use dehumidifiers to manage humidity levels, preventing condensation and mould growth.

Monitoring Devices: Install humidity sensors to keep track of moisture levels in the basement.

Insulation Options for Tanked Basements

Type of Insulation: Choose insulation materials that are resistant to moisture, such as closed-cell foam or specific insulation boards designed for damp environments.

Installation: Ensure that insulation does not compromise the tanking system. It should typically be installed on the room side of the waterproof membrane.

Energy Efficiency: Proper insulation not only makes the basement more comfortable but can also improve the energy efficiency of your home.

Electrical and Plumbing Considerations in Tanked Basements

Safety First: Electrical installations in a basement need to comply with UK wiring regulations, especially given the increased risk of moisture.

Waterproof Fixtures: Use waterproof sockets and light fixtures to prevent moisture-related damage and hazards.

Plumbing Adjustments: Any plumbing work, such as rerouting pipes or installing new fixtures, should be done with the waterproofing system in mind to avoid breaches.

Legal and Safety Aspects of Basement Tanking in the UK

Building Regulations: Ensure that your tanking project complies with UK building regulations, particularly regarding ventilation, fire safety, and structural integrity.

Planning Permission: In some cases, especially if altering the structure or use of the basement, planning permission may be required.

Professional Assessment: Consider consulting with a structural engineer or a waterproofing specialist to ensure all work is safe and compliant.

Frequently Asked Questions

The cost of basement tanking in the UK varies widely based on factors such as the size of the basement, the method of tanking used, and the complexity of the job. On average, you might expect to pay anywhere from £70 to £150 per square metre. However, for a more accurate estimate, it’s best to obtain a quote from our professional, as we can assess your specific needs and provide a tailored price.
A properly tanked basement in the UK can last for many years, often over a decade, provided it is correctly installed and maintained. The longevity largely depends on the quality of materials used, the proficiency of installation, and ongoing maintenance practices. Regular inspections and timely repairs can significantly extend the lifespan of a tanked basement.
While some aspects of basement tanking can potentially be done as a DIY project, particularly if you have some experience in building work, it is generally advisable to engage a professional. The complexity and potential risks associated with incorrect tanking are significant; a professional can ensure that the job is done correctly, thereby reducing the risk of future dampness or structural issues. For peace of mind and guaranteed effectiveness, professional installation is recommended.

Not all underground spaces require tanking. The need for basement tanking depends on various factors, including the level of groundwater in your area, local climate conditions, and the historical presence of dampness in your basement. If you’re unsure whether your basement requires tanking, it’s a good idea to consult our waterproofing specialists who can assess your particular situation and provide expert advice.

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