What is tanking?
Tanking is a term that refers to damp proofing walls retrospectively by creating a complete water-impermeable barrier covering the entire wall. It is usually employed as a remedial method in situations where there is no access to the external wall of the structure, such as in basements and cellars.
Methods of tanking can be divided into two main types. The first is by an application of a damp proof membrane (DPM) to the interior wall. This method in itself can be split into two types. The first of these consists of fixing sheets of polypropylene membrane to the wall with special membrane clips. The separate sheets are bonded with tape to create a complete seal and the membrane is then plastered over.
A DPM for tanking walls may also come in liquid form as a two part epoxy based membrane. This is applied directly to the underlying brickwork or masonry in two coats. The resulting waterproofed surface may then be rendered, plastered or painted directly.
The second main type of tanking is referred to as Cementitious Tanking. Cementitious just means that something is like, or pertains to, cement. With cementitious tanking the wall of the structure is stripped back to the base material and then re-rendered with several coats of a sand/cement render mixed with special damp proofing products.
Cementitious tanking is normally used where the likely ingress of water is considered to be less than something that would require the fitting of a DPM. The advantage of a cementitious tanking system is that it is vapour permeable. As the movement of water vapour is generally outwards from the basement or cellar this allows the room to breathe.
Cementitious tanking systems normally require a period of curing for around a month before it is possible to decorate over them. It is important to note that any decorative coverings applied over the top of cementitious tanking must also be vapour permeable. This prevents a build up of humidity within the plaster (known as interstitial condensation), which can cause damage such as blistering and peeling to the decorative covering. As a rule of thumb, it is generally considered that glossy, oil based paints are not suitable whilst water based emulsions are.
If you have damp problems in a cellar or basement, or are considering a basement conversion and are concerned about possible damp proofing issues, contact a damp proofing specialist like us here at London Damp Proofing who will be able to advise you on which, if any, tanking system is suitable for your circumstances.
Contact us today on: 077 0908 4010
Unit 142 Culvert Court, Culvert Road, London, SW11 5AU