WATERPROOFING : How to waterproof a pond

by Media Xpose

This DIY article is compliments of well-known construction chemicals producer, Sika.

The process starts with selecting the right materials for the job. In this article, the emphasis is on the use of Sika materials, although much of the advice given is generic to the task as hand – all you need to do is read the instructions on the label of product you buy and also be guided by the advice given at your friendly local hardware store.

Materials and equipment needed

Irrespective of product brands used, you will need:

  • A universal waterproofer and bonding agent
  • A membrane, normally made from a bonded PET or other polymer fibre
  • Portland cement, standard grade
  • A large painter’s bucket or bath to wet the membrane in
  • A wire brush
  • A block brush or a large paint brush – depending on the size of the pond.
  • A spatula for mixing small quantities or a mechanical mixer for volumes great than 5 litres.
  • PPE, such as rubber gloves (cement can damage the skin) and a safety mask (wet product gives off a gas).
  • A source of water.

Step 1: Empty your pond and make sure that it is dry before you start. Clean the area with a wire brush and wipe away any dust or loose material. Ensure that there is no algae or plant growth. Repair any visible cracks before applying the waterproofing system.

Step 2: Measure out the selected membrane, such as Cemflex® Membrane, to fit the surface completely. Precut manageable pieces of membrane for the required area.

Step 3: Using the mixing guideline, prepare the products in a bucket to form the waterproofing Cemflex slurry. First mix the required amount of Cemflex and water and then add the correct amount of Portland cement slowly, while mixing, to avoid lumps forming. You will now have slurry that is ready to be applied.

If using the Sika product, Cemtex, proceed as follows:

Mix 1 litre of Cemflex (universal waterproofer and bonding agent) with 3.4kg of Portland cement, with 1 litre of water and stir well. This will provide slurry that will cover an area of one square metre in combination with the membrane.

Step 4: Soak Cemflex Membrane in the Cemflex slurry. Dampen down the surface, making sure that there is no standing water. While the surface is still damp apply a coat of the slurry using the block or paint brush. Soak the membrane in the slurry well.

Step 5: Remove the membrane and squeeze lightly before placing over the damp substrate with your gloved hand, smoothing off with the brush to eliminate air bubbles. Overlaps of adjacent fabric should be at least 50mm.

Step 6: Final waterproofing coat of Cemflex. Once the entire area is covered and all the air bubbles have been removed, apply a generous second coat of the Cemflex slurry and allow to dry for 24 hours.

Step 7: After 24 hours, mix a new batch of the Cemflex slurry and apply the final coat to the completed area. Freshly applied Cemflex should be protected from damp, condensation and water for at least 12 hours. Allow at least 24 hours before filling your pond with water. Please take note that cold weather conditions can have a big effect on drying times, so please take that into account when starting your project

Once completed, the surface must be thoroughly cleaned and the pond rinsed out. Fill the pond and ensure that the water is properly conditioned before use. You may want to consider first introducing plant species to the pond, to allow biological processes to start work in in preparing the water for the fish.

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