A complete guide to tanking a wall

If you need to damp-proof your home, wall tanking is a highly effective way to do it. Here at Build & Plumb, we’ve created a guide to tanking a wall, including your step-by-step process for applying tanking slurry.

What is tanking a wall?

Wall tanking refers to the process of creating a protective, watertight barrier on internal walls to prevent damp and water ingress.

Damp walls are a serious issue that can affect the integrity of the building, damage the property and cause health issues. 

There are several factors that can lead to damp, including:

  • Penetrating damp, when water seeps through an external wall.
  • Rising damp, when moisture from the ground travels through the walls.
  • Condensation around windows and doors.

Though tanking slurry cannot treat rising damp (you’ll need a special damp proofing course for this), it is a highly effective method of preventing penetrating damp.

Penetrating damp can happen for lots of reasons. For example, building faults like poor window structure or a damaged roof can allow rainwater in. Plumbing issues like a burst pipe are also common causes. In old houses especially, cracks in the brickwork and damage to the exterior walls are another leading cause.  

You can identify penetrating damp by damp patches on your ceiling or walls, paint bubbling and localised black mould patches. Black mould can also smell, so be sure to check behind furniture if you identify an odour but can’t immediately see the cause.

Tanking wall (1)

What is tanking slurry?

Tanking slurry – also known as cementitious tanking – is a popular method for tanking a wall.

It’s a specially designed thick liquid made from cement, aggregates and chemical modifiers that creates a waterproof coating on masonry. Tanking slurry works by filling the pores and capillaries in the wall and, once set, forms insoluble crystals that block them, creating a watertight barrier.

Tanking slurry can be applied to different surfaces, including brick, concrete, stone and cement. It can be suitable for a range of applications, including:

  • Retaining walls
  • Basements and cellars
  • Garages
  • Bathrooms and kitchens
  • Swimming pools
  • Fish ponds

How to apply tanking slurry

Tanking slurry comes in powder form that you mix yourself. It’s applied in a two-coat process. Here’s how:

  1. Before applying the tanking slurry, you need to strip the wall back to the original masonry. This includes removing any plaster, render, layers of paint and any loose mortar. You can use a wire brush or pressure wash for this.
  2. Repair any cracks or holes in the wall.
  3. Brush down the surface to remove any dust and debris.
  4. Fully wet the walls (this will help the tanking slurry adhere).
  5. Wear a protective mask before mixing your tanking slurry, as the chemicals can be harmful.
  6. Following the manufacturer’s instructions, mix your tanking slurry with water in a bucket until it has a consistency like plaster.
  7. Apply your first coat evenly in horizontal brush strokes using a masonry brush. Apply this as quickly as possible, as it will start to set within 45 minutes.
  8. When the first coat is dry to the touch, apply a second coat, this time in vertical brush strokes. Always apply the second coat within 24 hours.
  9. Leave this second coat to cure fully.

How long does tanking slurry take to dry?

Generally speaking, the second coat should cure within 24 – 48 hours. Temperature and ventilation both affect tanking slurry drying times. Cold temperatures and poor ventilation will lengthen the amount of time it takes to dry. 

The time you need to wait before rendering over tanking slurry may vary between brands, so check the manufacturer’s instructions.

Some areas of the wall may also take longer to dry than others, and you may notice some sweating. This is caused by condensation on the cold surface and is normal during the curing process.

Tanking slurry at Build & Plumb

Now you know how to apply tanking slurry, you can ensure a professional finish and keep your property free from penetrating damp. 

Ready to get started? Here at Build & Plumb, we have all you need for tanking a wall. Shop a wide range of tanking slurry from leading and trusted manufacturers including KA and Bostik.

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