Waterproofing your home is essential, especially when moisture and dampness cause serious structural issues.
External tanking is one of the most effective methods for preventing water ingress, particularly in below-ground areas like basements and cellars. This technique offers long-lasting protection against water penetration for homes in regions prone to heavy rainfall or high water tables.
This guide will take you through the entire process of external tanking, from understanding what it involves to the materials used and the benefits it provides. Proper application and maintenance of external tanking can save homeowners from expensive repairs and ensure a dry, safe living environment.
Let’s get straight to the point.
External tanking is a waterproofing method to protect buildings, particularly basements and below-ground structures, from water ingress. It involves applying a waterproof barrier to the exterior of the walls, preventing moisture from entering the building.
Common materials include cementitious slurries, bitumen, liquid waterproofing membranes, and drainage systems. The process includes surface preparation, material application, and final inspection.
External tanking stops water before reaching the interior more effectively than internal tanking, though it requires more effort. Regular inspections and maintenance ensure the system remains effective.
Importance Of External Tanking
Waterproofing is essential in maintaining the structural integrity of underground spaces like basements, as these areas are constantly exposed to water pressure from the surrounding soil.
Water seeping into the foundation can cause dampness, mould growth, and structural weakening over time. By applying external tanking, you create a protective shield that keeps these issues at bay.
Benefits Of External Tanking
1. Complete Waterproofing Solution
External tanking is one of the most comprehensive methods of keeping water out of basements or underground structures.
By tackling the issue from the outside, it prevents water from even reaching the structure.
2. Durability
A well-installed tanking system can last decades, providing long-term protection against water damage.
The materials used, especially polyethylene-backed membranes, are tough and durable, able to withstand the pressures of groundwater and soil.
3. Suitable For New Builds And Retrofits
External tanking is versatile and can be used in new constructions and retrofitting buildings.
This system is essential to ensure damp-free conditions when renovating or converting a basement into a living space.
Choosing External Tanking
1. New Builds
External tanking is preferred for new constructions, especially when building below ground level. It provides a comprehensive waterproofing solution from the outset.
2. Renovating Basements
External tanking ensures a basement remains dry and habitable when converted into a living space.
It’s a more effective and long-lasting solution than internal systems, particularly in areas with high water pressure.
3. High Groundwater Areas
In regions with high water tables or where heavy rain and flooding are common, external tanking offers the best protection against water ingress and dampness.
Materials Used In External Tanking
Different materials are available for external tanking, each suited to specific types of construction and conditions.
These materials create a waterproof barrier that protects the structure from moisture.
1. Cementitious Tanking
Cement-based tanking is one of the most common forms used for waterproofing. It is applied as a slurry directly onto the exterior walls. This material is favoured for its durability and resistance to pressure, making it suitable for new builds and retrofits.
- Advantages: Cementitious tanking is cost-effective and easy to apply, providing a solid, long-lasting barrier.
- Disadvantages: It may not be flexible, meaning it can crack under structural movement.
2. Bitumen-Based Products
Bitumen is a sticky, black material often used in external tanking. Bitumen-based tanking is applied in layers to form a flexible and durable barrier.
This type of tanking is ideal for areas where some movement is expected, as the bitumen remains flexible after application.
- Advantages: Highly durable and flexible, bitumen tanking is excellent for use in areas prone to ground movement.
- Disadvantages: It can be more expensive than cementitious options and requires a professional application.
3. Liquid Waterproofing Membranes
Liquid membranes are applied as a coating that dries to form a seamless, waterproof layer. This type of tanking is often used in modern builds due to its ease of application and flexibility.
Liquid membranes are commonly used with other waterproofing systems for extra protection.
- Advantages: Provides a seamless barrier that can be easily applied to complex shapes and areas.
- Disadvantages: Requires professional application and can be more expensive than other tanking methods.
4. Drainage Membranes
Drainage membranes are often used with external tanking to ensure water can be directed away from the building.
These membranes are applied to the exterior walls and allow water to flow through controlled drainage systems, preventing it from pooling against the walls.
- Advantages: Prevents water from accumulating near the foundation, reducing pressure on the structure.
- Disadvantages: Additional drainage system installation adds to the overall cost.
The External Tanking Process
External tanking involves several steps, from preparing the surface to applying the waterproof barrier. Ensuring the process is done correctly is important to provide full protection from water ingress.
1. Surface Preparation
Before tanking can begin, the surface of the walls must be thoroughly cleaned and prepared.
This ensures the waterproofing material can adhere properly to the surface and create an effective barrier.
- Cleaning: All dirt, dust, and debris must be removed from the walls. This may involve power washing or scraping.
- Repairing Damage: Repair any cracks or holes in the wall before applying the waterproofing material. This helps ensure a smooth, even application.
2. Applying The Tanking Material
Once the surface is prepared, the chosen tanking material is applied. Depending on the material used, this can be done using brushes, rollers, or spray systems.
Multiple layers are often applied to ensure full coverage and create a strong, effective barrier.
- First Coat: The first coat acts as a base and must dry fully before applying the second layer.
- Second Coat: A second layer is applied to reinforce the waterproof barrier and ensure no gaps or weak spots remain.
3. Installing Drainage Membranes
In cases where a drainage system is required, drainage membranes are installed after the tanking material has been applied.
These membranes direct water away from the building’s foundation, ensuring it does not accumulate and create pressure against the walls.
- Membrane Placement: The membranes are placed along the base of the wall, ensuring water is directed away from the building.
- Drainage Installation: A drainage system may carry the water away from the foundation and prevent it from pooling around the structure.
4. Final Inspection And Finishing
Once the tanking process is complete, a final inspection is carried out to ensure the waterproof barrier is fully intact.
Any weak spots or missed areas are repaired, and the site is cleaned up.
- Inspection: The tanked area is inspected for gaps or cracks that could compromise the waterproofing.
- Backfilling: If tanking is applied below ground, the area around the foundation is backfilled with soil or gravel.
Conclusion
External tanking is a highly effective method of waterproofing a structure, particularly in areas prone to dampness and water ingress. By applying a protective barrier to the exterior walls, homeowners can prevent water from penetrating the building, thus avoiding costly damage.
The choice of tanking material, such as cementitious products, bitumen-based membranes, or liquid coatings, will depend on the structure’s specific needs. Regular inspections and maintenance ensure the tanking system’s long-term success.
By catching minor issues early, homeowners can protect their properties from serious water damage, ensuring their homes remain dry, safe, and structurally sound for years.
FAQs About External Tank
Is Tanking The Same As Waterproofing?
The distinction between waterproofing and tanking in a building. Generally, when people talk about waterproofing their basements, they mean all different kinds of waterproofing systems (barrier, integral and drained). Applying a particular coating or membrane is referred to as tanking the basement (barrier protection).
Will Tanking Stop Damp?
Tanking a room can be an effective method for addressing mould and dampness issues and preventing water from accessing your structure. If your inner walls are colder than your outer walls, condensation may collect on them. If you do not have sufficient ventilation, mould may grow on the condensation-covered inner walls.
How Do You Prepare A Wall For Tanking?
The first thing to do is brush out any dust on the walls and then remove any damaged or outdated plaster, paint, or render. After cleaning the wall, adding a salt neutraliser will stop any hygroscopic salts from penetrating the tanking slurry that will be applied shortly.
Can You Tank An Outside Wall?
The tanking slurry can be applied to a moist wall above the ground to prevent water from seeping. Before applying it, it is highly recommended that you locate and eliminate the cause of the dampness first. Tanking slurry can also be used by itself as a Type A Waterproofing method in areas below ground (barrier system).
What Is Tanking In Building Terms?
Tanking, also known as below-ground waterproofing, is the process of applying a waterproofing barrier to the walls, base slab, and, in certain instances, the roof of a structure located below the earth. It is sometimes known as “tanking.”
