Being below ground, basements and cellars are susceptible to groundwater being forced into the structure under pressure. Factors such as type of structure, depth of the structure, the makeup of surrounding soil and location of the structure all play a part in how much dampness or water ingress is experienced by the basement or cellar during the course of its lifetime. The types and levels of basement waterproofing are just as numerous as the causes of dampness and it is essential that all factors are taken into consideration when designing the waterproofing system.
Commonly referred to as either basement tanking or structural waterproofing, a systematic and thorough approach is needed at the design stage to ensure that all remedial works not only adhere to British Standards (BS8102:2009) but achieve the intended results.
Type A basement waterproofing also known as tanking, it is an externally or internally applied barrier system applied to the walls and floors of the structure that can withstand ground water from entering the building under pressure. There are numerous products and methods for applying Type A waterproofing systems including sheet membranes, multi-coat renders, crystalline slurries and bitumen based coatings. A thorough assessment of the structure must be carefully assessed at design stage to ensure its suitability. This system requires the structural elements of the building to be strong enough to withstand ground water pressure.
Type B waterproofing is an inbuilt characteristic of the actual structure by adding waterproofing additives to the concrete used to form the floors and walls of the structure. Although normally effective in its own right, the joints of the structure are it’s weak spot and as such are susceptible to water penetration. Type B waterproofing is normally backed up by combining type A, C or sometimes both to ensure a watertight system and minimise risk. Type B basement waterproofing is normally specified in newbuild below ground structures.
Type C waterproofing is essentially a set of dimpled membranes called Cavity Drain Membrane (CDM) installed externally or internally to the walls and floors of the basement structure. A type C basement waterproofing system does not aim to prevent the incoming water to the structure but instead manages it and diverts it into either a pumping chamber or external land drain. This system is suitable for all structure types and is quickly becoming the preferred system for existing cellars and basements that are subject to ground water ingress due to its relatively low risk of defect and ease of installation.
To book a site survey, consultation and no obligation quotation on our cellar/basement waterproofing services throughout London, please use our online contact form or call us on: 020 8959 6424.
Basement waterproofing, also known as Structural Waterproofing is a Waterproofing system designed to prevent groundwater ingress into the structure under pressure. There are various methods of basement waterproofing and each has its own set of requirements to ensure success.
Ground Water, as its name suggests is water held within the soil and geological cracks. This water is normally moving in a certain direction dependent on the topography of the local area. Ground water can be increased with heavy rainfall as this water permeates the top soil and enters the water table.
A water table is essentially a pond or series of ponds within the geological topography. In London for example, we have 2 water tables. The first being at bedrock level which is potable water and the second being called a perched water table which sits ontop of the London clay basin. These water table levels fluctuate from year to year.
Any structure that is set into the ground surrounded by high ground levels on 1 or more sides is subject to ground water pressure bearing on the structure, if left untreated, this ground water can enter the structure under pressure and cause surface dampness to walls and floors or potential flooding. It is imperative to prevent ground water ingress that a below ground structure is correctly waterproofed.
In a nutshell, Very! Each property is unique in one way or another. It important that the property is correctly assessed and the subsequent waterproofing system is designed in accordance with the construction type and falls in line with BS8102(2009). A surveyor with the accreditation CSSW, (Certified Surveyor in Structural Waterproofing) is qualified and experienced to assess, specify and install the correct waterproofing system based on the structural requirements.
BS8102(2009) Is a code of practice for structures below ground. Providing guidance and recommendations for protecting this structure against ground water. Any waterproofing system that is designed and installed to a below ground structure, should adhere to BS8102(2009). Further information can be found here
There are primarily 3 waterproofing systems that can be installed to a below ground structure. We call these Type A, B & C. Each of these, as explained above have certain requirements to ensure the correct design and application. These types can be mixed into a combination system utilising 2 or more systems to achieve the required result.
Type A Waterproofing is a waterproofing system that can be externally or internally applied to the structure which barriers ground water from entering the structure. A Typical Type A waterproofing system can comprise of cementitious waterproofing slurries and renders along with bonded membranes. Typically, this type of system is referred to as Tanking.
Type B waterproofing is a waterproofing system that is inherent within the structure such as a concrete new-build property in which waterproofing additives have been used in the mixing of the concrete along with hydrophilic waterproofing junctions and construction joints.
Type C waterproofing is a water management system that utilises a set of internally or externally applied dimpled membranes along with drainage channels and pumps to manage any ingress of ground water into the structure and keeping it away from the internal living space. This system is referred to as a Cavity Drain Membrane system, or CDM for short.
The cost of Basement waterproofing varies dependent on the type and size of structure that requires waterproofing along with the Type of waterproofing that is required for the structure. Please contact us for further information and we will be able to assist you with your requirements.
Typically, Basement waterproofing guarantees last for 10 years providing the waterproofing system has been maintained and serviced in accordance with company and manufacturers instructions. These guarantees can also be underwritten by a third party insurer for that extra peace of mind.
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