Contiguous Piling and Diaphragm Walls
The use of contiguous / secant piling and diaphragm wall construction techniques to construct retaining walls is common in large commercial basement projects and often an efficient and cost-effective solution. The nature of these construction techniques is such that the only practical option is to apply waterproofing systems to the internal face of the retaining wall in order to reduce the risk of groundwater ingress between the piles.
Safeguard offers a choice of systems for waterproofing Type C waterproofed basement retaining wall. These are:
Choosing which system to use will depend on a number of factors including site conditions, drainage options, and personal preference. Typical waterproofing methods using both systems are described on this page.
This system allows water to permeate through the basement retaining wall, but redirects it away from the internal wall of the basement towards a sump or other suitable discharge point. For this type of application, a cavity drainage membrane with a large stud size such as Oldroyd Xv 20 is usually preferred in order to cope with the higher potential flow rates required for larger basement projects.
This type of waterproofing system can be used on contiguous / secant piling as well as diaphragm walls. In accordance with BS 8102:2009 the structure should offer primary resistance, regulating the volume of water entering the basement, in order not to exceed the drainage capacity of the system. However, from a waterproofing perspective, contiguous piles are not, and should not be considered as a tight structure. Therefore, relying solely on the application of a cavity drainage system on the piles is not recommended.
Other suggestions on how to improve the water tightness of retaining walls can be found in the ICE publication, “Specification for Piling and Embedded Retaining Walls” [1]
When applied to Type A waterproofing system concrete retaining walls, Vandex waterproofing slurries create an impervious barrier, blocking the passage of groundwater into the basement. Because the types of basement retaining wall described on this page are constructed from concrete, Drybase Crystalline Active Tanking Slurry is usually selected as the waterproofing slurry. Drybase Crystalline Active Tanking Slurry is specifically designed for the waterproofing of concrete and offers a higher coverage rate than other Drybase waterproofing slurries, making it an economic choice.
When waterproofing diaphragm walls, Drybase Crystalline Active Tanking Slurry is simply sprayed onto the internal face of the wall. When waterproofing contiguous or secant piling, the Drybase waterproofing layer is typically sandwiched between a layer of shotcrete and a poured concrete internal wall (see Figure 2)
This method of waterproofing is dependent on the strength of the underlying piles and the tolerances between them than the Oldroyd method (see Figure 1). It should only be used in conjunction with reinforced concrete as shown in the diagram above.
Combined Type A and C waterproofing systems are often desirable when waterproofing basements. BS 8102:2009 “Code of practice for protection of below ground structures against water from the ground” suggests that “combined protection” should be considered where the assessed risks are deemed to be high (e.g. permanently high water table) or the consequences of failure are high. NHBC Chapter 5.4 states that where Grade 3 protection (BS 8102:2009) is required, and below ground wall retains more than 600 mm, measured from the lowest finished floor level, the waterproofing design should include a combination of two types of waterproofing systems. Therefore, Drybase and Oldroyd systems are usually combined (see Figure 3).
A wide variety of combination systems can be specified depending on the type and quality of the retaining wall. For example, in certain situations it would be possible to omit the reinforced concrete wall from the example above. For further details, please contact our technical department on 01403 210204 or submit an enquiry.
[1] “Specification for Piling and Embedded Retaining Walls 2nd edition” Institution of Civil Engineers – ISBN: 9780727733580
How can we help?
Related Pages
A liquid polymer additive for Drybase TS-Plus to enable basement waterproofing.
Read moreWith Tibby Singh and YDC Basements, Safeguard waterproofed a basement at an end of terrace home in Leeds using Drybase Tanking System.
Read moreA durable and easy to apply layer for domestic and commercial applications on concrete and brick surfaces.
Read moreBuilt in Summer 1940, the Type 26 pillbox is a 6 ft by 6 ft cube just big enough to house 4 soldiers and their guns. The 1 m thick concrete walls were built to withstand a direct hit from a naval warship. 98 tons of concrete went into creating the pillbox. In the 1980s, the whole exterior was covered…
Read moreA simple, long-lasting solution to protect masonry from penetrating damp is the use of a masonry sealant, like Stormdry Masonry Protection Cream. Masonry sealants protect walls against penetrating damp and thus prevent dirt and moisture ingress through rainwater. Stormdry is a cream-based masonry sealant, which protects building materials for 25 years against penetrating damp – with just one coat. The…
Read moreFleas are traditionally active from April through November, but modern central heating has led to them becoming an all year round problem. They spread discomfort, disease and infection that can affect humans and animals. Regardless of the time of year, your home can become flea-free with careful planning and a rigorous treatment regimen!
Read moreWhen Emerald Damp Specialists stepped inside a severely damp bungalow in Swindon, they knew they had to help. Along with 70 other companies and over 150 volunteers who donated their time and expertise, Emerald Damp Specialists resolved the extreme damp and mould problems at the property free-of-charge. For this project, ensuring that a valued member of the community had a…
Read moreTraumatic damp is defined as dampness caused by a building defect that lets moisture into the home.
Read moreSubscribe to get information about products and offers.