How to tank a cellar

How to tank a cellar

How you go about tanking a Cellar is determined by two key points. First point is what use do you want to put the Cellar to. In basic terms, do you want to create some additional storage so you can free up some space in the main living area or do you want to create some habitable space such as a Games room or a bedroom.

Once you have decided on the use for the Cellar you then have to establish the risk of dampness or even the risk of flooding.

These decisions pretty much determine the method of tanking.

There are three ‘tanking’ systems available for the internal walls of a cellar. They are:

1) Tanking slurry or render otherwise called Cementitious tanking. A one component compound you add water too and apply by brush or trowel.

2) Liquid paint on membranes that once dry form to a seamless membrane on walls and floors.

3) Cavity drain membranes which are in basic terms a dimpled plastic sheet system intended to manage water ingress or allow damp to evaporate behind the membrane.

If you simply want to damp proof a Cellar to store some tools, gardening equipemnt, etc and the conditions are pretty dry then tanking slurry or damp proof paint are fine for the purpose. The key to success is getting a good bond with the product you are applying to the wall and floor you are applying it on. For instance, there would be no point in applying these products to a previously applied damp proof paint which is peeling and blistering as the bond of your product will only be as good as the bond of the old system.

The key to these types of products are low risk of damp or water ingress and thorough preparation of the walls and floor to get a sound bond.

Always follow the manufacturers application instructions.

Be mindful that paints and renders allow water vapour through the walls and floor so you need to ensure you have some form of ventilation as otherwise metal items can rust or fabrics can get mouldy.

If you want to have a dry Cellar for storage but for high value items including important documents but have a relatively dry Cellar then I would go with the Cavity drian membrane system and batten out or put in a stud frame so in basic terms you have a dry lining system. This allows for the walls the breathe behind the membrane but no damp, water or vapour pass through. Very important to introduce ventilation to stop condensation behind the dry lining.

If you want to use your Cellar for habitable use you would be best advised to use Cavity Drain Membrane. Installed with a sump and pump and drainage channel provides you with a fully servicable system which if installed by an approved contractor would be supported by a 10 year guarantee. If the Cellar is dry the owner can make a decision on using drainage or not. If the risk of damp or water ingress is low then you can install membrane without a sump and pump but the only guarantees with this system would be a product guarantee for the membranes used.

We have helped and advised homeowners, builders, damp proofers, basement contractors and architects on the systems available and how to install them. For advice on your project call us on 01329 235252 and we will be pleased to help.