Cellar Tanking Membrane Ventilation

[Danny Monaghan]

I've been planning to do this job for two years now - the first year of that was before we even lived in the house :)

I'm going to tank our damp but not wet cellar using a membrane. I've been told that you leave the top on the membrane open at joist level to allow the wall to breath, so I assume that I will need to add plenty of ventilation at joist level (just above ground level in effect) to allow the damp to get away, but is there a better way to do it than adding a few air bricks round the house? Currently there are only three points the cellar can breath, and one of those is the coal chute so is not properly open because it has a cover on it.

BTW, I'm not talking about the ventilation for the rooms that the cellar will have after tanking - I was planning on using a humidistat controlled fan to vent those to keep any damp down.

The house is a 1902 9" solid brick wall built one.

Cheers.

[Phil L]

cross-flow ventilation is what it needs, and simply adding one or two extra

9 X 6 airbricks per elevation is the simplest, cheapest and most effective way of achieving this

[Andrew Gabriel]

I would do the ventilation first. That might turn out to be all you need to do.

[Hugo Nebula]

On Thu, 17 Apr 2008 14:41:51 +0100, a particular chimpanzee, Danny Monaghan randomly hit the keyboard and produced:

If you are you creating rooms down there, then you will need a proper tanking system (ie, one with a BBA certificate). A membrane won't do anything but trap the moisture on the inside of the wall with nowhere to go. You'll also need insulation to the walls and floors to comply with the Building Regulations.

There are essentially two ways of tanking a basement:

1. Preventing any moisture from penetrating the walls and floor. Waterproof material is added to the walls and floor, such as Vandex or Synthaprufe.
2. Allowing any water coming through the structure to drain away before it reaches the inner surfaces. A raised membrane (rather like an egg tray) is attached to the walls and floor allowing drainage behind, with a sump at low level to collect the water. This may need a pump to drain away.