How to tank a wall – Tanking project + Video

Tanking a wall, is the process of adding a layer of waterproof protection. This is designed to stop moisture penetrating its surface. Tanking is usually applied internally and can be done in a variety of different ways.

how to tank a wall

The most common ways to tank a wall include:

  • Using a membrane – This is attached to the surface and creates a waterproof barrier. It can be a great method; However, it often requires some kind of drainage, as the water still comes through the wall, and collects behind the membrane.

    In many cases, this can become quite complicated with floor gutters to run away the water. As well as pumps to remove the excess water from the room.

  • Applying a tanking slurry – This is a more basic method, but it is very effective. Tanking slurry is a cementitious coating that can be applied to a surface, in order to create a watertight barrier that is completely non-porous. This means it is impenetrable to water.

In this article and the video below, I will be showing you how to tank a wall with tanking slurry. The video shows the entire process from start to finish.

This includes, preparing the walls, mixing the tanking slurry, and applying the finished mixture to the walls.

Check the video below for the entire walk through or read the process below.

Tanking slurry project

The process of applying tanking slurry is actually very simple. It comes in a powder form, and you add water to achieve the correct consistency. Following this, it can simply be applied with a brush.

The amount of time this type of project takes, will often depend on the preparation, prior to applying the slurry.

If your walls are in good condition and free from dirt, debris, and other materials such as paint, then the job will be easier, and much less prep will be involved. On the other hand, if the wall is in poor condition, this will need rectifying first.

You should also fill any holes in the wall, this includes things like blown pointing, and shoddy, or damaged brickwork. It is much better to fill these bigger gaps with a sand and cement mortar, than to try and fil them with the slurry.

The tanking slurry is not designed for filling holes, its consistency is thinner and wetter than mortar. Also, your slurry is much more expensive than sand and cement. Therefore, it makes sense to fill these before tanking.

Once your walls are completely clean and any holes have been filled, you should wet the walls down. This is done for two reasons:

  • Firstly, it will remove any remaining dust from the surface, allowing the slurry to take hold better.
  • Secondly, it will reduce suction. By wetting the wall, you will stop the surface from pulling moisture out of the slurry.

Mixing your tanking slurry

Mixing tanking slurry is a pretty simple process, it comes in a premixed powder. This means, all you need to do is add water.

To do this, fill a bucket around ¼ of the way up with water, and start to add the slurry. This should be done gradually, in order to achieve the correct consistency. You can mix the slurry manually with a trowel or even a piece of wood.

However, I personally opted for a quicker method, using a whisk attachment for a cordless drill. If you already have a drill, I definitely recommend this option. A whisk attachment isn’t expensive, and it will save you a huge amount of time.

I ordered mine from Amazon, at the same time I ordered the tanking slurry. You can see a link to both items below:

Mixer drill bit

KA Tanking slurry

When mixing the slurry, your goal should be to achieve a silky, creamy finish. At this point, you should be able to stand a thick brush in the mixture, without it falling over.

If in doubt, I would recommend a slightly wetter mix, as opposed to a dryer mix. This is for two reasons:

  1. It will be easier to apply
  2. The slurry won’t go off as fast

How to apply tanking on your walls

Tanking the walls is very simple. This can be done with a brush, similar to how you would apply paint.

The slurry is cement based, so it doesn’t spread quite as well as paint, but it isn’t that bad to work with.

One thing you should remember, is the mixture will be going off as soon as you add water. Therefore, you need to get it on quickly, before it gets too stiff. You will notice it getting stiffer as you reach the end of a bucket, compared with the beginning.

Finally you will need to apply two coats. The best way to do this, is to apply one coat vertically and the other horizontally. This will ensure you get the best coverage and fill any gaps.

Once the tanking slurry dries, you will have a completely waterproof surface.


You now know how to tank a wall with tanking slurry. As you can see, this is very easy, and it can definitely be done as a DIY project.

There isn’t really any skill involved, so most people could make a good job of this. It isn’t the most fun job, and it is messy, and its quite hard work. However, it can easily be done in a day, and the end result is a really effective barrier against penetrating damp.