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Basement Waterproofing


Basement waterproofing encompasses various methods and techniques used to prevent water from entering a basement. Waterproofing can include both internal and external approaches. External waterproofing often involves applying a waterproof membrane or coating to the outside walls and foundation of the building, along with proper drainage systems to redirect water away from the structure. Internal waterproofing might include the application of sealants, the use of water-resistant materials, and the installation of sump pumps or drainage systems inside the basement to manage any water that does penetrate.


RJ Evans provide basement waterproofing services. This includes both existing basements and new builds. Our highly-experienced team cover all of London and the South of England, and are fully accredited waterproofing specialists.

If you would like a quotation or any information about basement waterproofing please get in touch with us or call us now on 01277 375 511.

Underground structures such as basements, cellars or vaults are always vulnerable to pressured groundwater penetrating through their structure; because of this, waterproofing systems are essential to stop basement areas from becoming damp, moist, uninhabitable spaces.

What Makes Basements Vulnerable To Moisture?

Whilst lots of us seek to expand our living spaces the decision to go under the ‘water table’1 (turning a basement or cellar space into an extra room) means we are entering a space that is under hydrostatic pressure produced by water in the ground surrounding the building. Unfortunately, if waterproofing is not in place the pressure of the water against the outer walls and floors of the structure can cause cracks or leaks that will then lead to damp issues inside basements.

What Can Be Done To Waterproof A Basement?

Of course, there are many factors affecting the level of water pressure and thus the level of dampness a basement or cellar is likely to endure through the course of its life, these include the type of building, the depth it reaches, its location and the composition of the surrounding soil. These factors are things that have to be assessed by a specialist and directly affect how they will design the waterproofing system to create an effective barrier, whilst also meeting with British standards; BS8102(2009)2.

Below we will explore three different types of waterproofing methods currently used.

Type A Waterproofing (also known as Tanking)

Tanking is a renowned method of waterproofing that has been used in the industry for many years. It is in essence a physical barrier that is applied to the basement or cellar walls to stop any moisture entering. This method of waterproofing is a barricade that can be applied internally or externally to a structure to act as a defence against the penetration of ground water.

There are many different approaches and products for creating a Type A waterproofing system including mastic asphalt. It is essential that thorough assessment of the structural needs be carried out by specialist during the design stage. This will enable specialists to determine which approach and what materials are most suitable to produce a structure strong enough to endure the level of ground water pressure it will face. However, typically the barrier they design can comprise of crystalline slurries3, sheet membranes, multi-coat renders and bitumen-based coatings.

Type B of Waterproofing (also known as Integrated Waterproofing)

Most commonly used as a waterproofing system for a concrete new build property, this type of waterproofing is intrinsic within the structure. To strengthen and protect the structure, waterproofing additives are added during the building process to the concrete and the building also has hydrophilic waterproofed junctions and construction joins; this is because the joints of a structure are typically the weaker spot in a building and thus more prone to water ingresses. To minimise risk of water penetrating the basement, a Type B system of water proofing is typically backed up by combining Type A or C of waterproofing into its design.

Type C of Waterproofing (also known as Water Management)

Often referred to as a Cavity Drain Membrane (CDM) this third type of waterproofing is a system that installs either internally or externally dimpled membranes into the walls and floor of basement together with a series of drainage channels and sump pumps. Any incoming water is then diverted through the channels and into a pumping chamber, thus effectively keeping it away from the internal living space. What is great about this system of waterproofing is that it is suitable for all structure types and can be used in pre-existing basements renovations and basement flats that come under pressure from water ingresses.

Key Basement Waterproofing Terminology Explained

Ground Water: This is water that is found underground and is stored in the soil and cracks, the direction this water moves on is dependent upon the topography of the local area. With heavy rainfall the ground water level is increased and this is when the water is more likely to saturate the top soil and join the water table.

Water Table: This is an underground boundary that separates the groundwater area from the soil surface; water table levels do change year to year.

Hydrostatic Pressure: The term given when the pressure given from a fluid matches the force of gravity creating an equilibrium.

BS8102(2009): This is the code of practise for underground structures which outlines the guidelines and recommendations on how structures are to be protected against groundwater. All waterproofing systems have to adhere to the standards outlined by BS8102(2009).

Common Questions About Basement Waterproofing

How Much Does Basement Waterproofing cost?

The factors influencing quotes for basement waterproofing are the style and size of the structure and also the type of waterproofing that is needed. Please do not hesitate to contact us for further information we will be happy to assist you with any questions and discuss your basements requirements.

How Long is Basement Waterproofing Guaranteed For?

Most basement waterproofing systems come with a 10-year guarantee as long as it has been maintained and serviced as outlined in the manufacture handbook. Should you want further reassurance guarantees can also be underwritten by a third-party insurer.

Get In Touch For More Information Regarding Basement Waterproofing

If you would like RJ Evans to help you with a quotation or any information about waterproofing your basement please get in touch with us or call us now on 01277 375 511 one of our friendly team will be happy to assist you.