Resolving Dampness in

Your Basement

The most common dampness found within a basement is penetrating dampness. Methods have improved over the years and we can now look at waterproofing as opposed to damp proofing.

British Standard 8102

British Standard 8102 is the British Standard relating to basements. There are different grades in relation to basements, for example:

Grade One is for a garage

Grade Two is for a working area, i.e. a plant room

Grade Three is a residential grade

Grade Four is basically Grade Three with relative humidity control

There are various options for damp proofing your basement:

Type A – Tanked Protection

Type B – Integral Waterproofing

Type C – Drained Cavity Protection

We will now consider the three options in turn:

Tanked Protection Type A

This is where a waterproof membrane is added to keep water out, for example within a Victorian property basement.

Integral Waterproofing Type B

This is where waterproof concrete is used, for example when building a bridge that needs to sit in water.

Drained Cavity Protection Type C

This is a dry wall system with a drain behind it and is said to be the best type.

This is an Overview of what each System Requires

Tanked Protection Type A

This involves adding a lining to the area, usually internally (as this is easier / cheaper) but sometimes externally. This can, if not carried out properly, add bending stresses which cause cracking to the tanking and as such a Structural Survey should be carried out to establish the construction and its attributes and whether it is capable of coping with the change in pressures as walls, which are normally brickwork and are strong in compression but not in tension.

We would add that this can move the damp problem around rather than resolve it. Although this does not form part of the presentation we thought we would add it to give a balanced view.

Tanked protection can be carried out by a general builder rather than a specialist builder; this can equally be an advantage or a disadvantage. It does mean that if you are having other building work carried out it can be incorporated into the work programme. If the tanking is used on the outside of the wall, whilst difficult to carry out due to the digging down the side of the property that is required, it does put the protection in the right place.

Integral Waterproofing Type B

This tends to be used on commercial applications and requires specialist design and knowledge.

Drained Cavity Protection Type C

The main key benefits are that it doesn't affect how the structure works, i.e. no added pressures; it is relatively easy to retrofit; and it resists vibration, unlike the tank. It has been used for 10 – 15 years, so now we have historic evidence on how it works.

Drained Cavity Protection Installation Process  

•  The sump is formed

•  Membranes added to the wall

•  Drainage channels are added

•  The close cellular insulation is added

•  The water proofing membrane (with a shallow or deep stud depending upon the configuration of the area)

•  The floor system

•  The finished wall

•  The pump is added into the sump

This article is based on a presentation by Dr Peter Fitzsimons as well as various other sources.

The presentation was given to the Independent Surveyors Association (ISA)

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