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‘Basement drainage’ is a broad term that can refer to the removal of water either as a part of or in order to assist with the waterproofing of the basement.

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Cavity drain waterproofing with inspection port

Internally, with Type C cavity drain waterproofing systems, drainage is an absolute requirement, whereas externally, when used to prevent water from bearing against the structure, the use of drainage can vary from very helpful, to not so helpful, and in some cases to dangerous.

The following article explains in detail the different forms of basement drainage and when they should and should not be used.

Basement Drainage Solutions

Internal Drainage Solutions

As the most recommended and most comprehensive waterproofing solution, the Newton CDM System includes a network of Newton Basedrain drainage channels that play an integral role in receiving water that is captured by the cavity drain membranes.

Captured water is then safely removed from the property either via a Newton Pumping System, or by safe gravity drainage to a point that is downhill of the basement slab.

Basement Drainage Solutions

External Drainage Solutions

When designing a continuous external waterproofing system such as Newton Hydrobond®, a key component is the drainage membrane that can be used in order to both protect the waterproofing wall membranes against damage, and to manage ground water to prevent it from bearing against the primary waterproofing.

The Safe Use of External Drainage

When specifying external drainage, some of the technical areas to consider include:

Basements Built Within Sloping Ground  

Basements built into slopes will break into existing watercourses and act as a dam to water that would otherwise have flowed downhill. Any such structure should therefore always use a drainage system around the basement.

Basements Built Within Flat Ground  

For such structures it is vitally important that the external drainage does not artificially dewater the ground. As such, a good geotechnical understanding should be obtained following a comprehensive study of the surrounding ground.

The Dangers Of Using Drainage Around Basements  

It is generally not good practice to use dewatering as a waterproofing method, as:  It is impossible to calculate how much water needs to be removed in order to prevent it bearing against the structure.  If the water has nowhere to go, groundwater could surround the basement to its full height.

Soakaways are not necessarily guaranteed to remove water from the ground around the basement, especially if it is saturated.  It is extremely difficult to use pumps for dewatering when it is impossible to know how much water needs to be pumped.  Overall, if the basement is being constructed within flat or level ground then drainage and Type A waterproofing cannot and should not be relied upon as the only method of keeping the basement dry.

The Dangers of Dewatering With External Drainage  

When building within flat, permeable ground, as water is removed it will be replaced by water from the surrounding ground. As this water moves, it brings with it fines from the ground; the smallest soil particles that bind it together. By constantly removing the water and therefore the fines as well, the soil gradually becomes less dense and, if enough is removed, then the ground surrounding the basement can become unstable.

WaterproofingWhy Should Combination Waterproofing Be Used?

The British Standard for Waterproofing (BS 8102:2009) recommends the use of combined waterproofing systems in order to provide enhanced protection. In cases where the basement is built within a slope, both of the drainage methods mentioned in this article may be installed on the same project to ensure maximum protection.

Drainage

Guaranteed Waterproofing Installations 

Newton highly recommends that installation is undertaken by a Newton Specialist Basement Contractor (NSBC). NSBCs can provide a substantial insured guarantee and take full design liability on the project, fulfilling the role of ‘Waterproofing Specialist’ as recommended by BS 8102:2009.

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Speak to our friendly, expert team

Our staff are able to provide guidance for projects of all sizes, whether you require some general advice about damp or waterproofing, or support with technical drawings and specifications.

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