Swimming Pool Waterproofing in London

Waterproofing is one of the most critical stages in building a reinforced concrete swimming pool. Without it, even the strongest concrete shell will eventually leak, causing expensive damage. At The Swimming Pool Company in London, we follow a meticulous, multi-stage process to guarantee a watertight pool that stands the test of time.

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Step 1: Surface preparation

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Proper preparation is the most important part of the waterproofing process and helps the membrane bond to the concrete. 

• Cleaning the surface – removing all dirt, dust, laitance, and debris using pressure washing, sandblasting, or grinding.

• Repairing imperfections – cracks, voids, and honeycombing are repaired with polymer-modified mortars. For fine cracks under 3mm, specialist crack fillers are used.

• Reinforcing vulnerable areas – waterproofing mesh or tape is applied to joints, corners, seams, drains, and any points where different materials meet.

• Moisture testing – the concrete’s moisture content is checked (must be 4% or less) to ensure the membrane bonds correctly.

 

Step 2: Apply the proprietary tanking system

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Once the surface is prepared, the waterproofing membrane is applied. Several types exist, including cementitious, liquid, and sheet-based systems. The manufacturer's instructions for mixing and application should always be followed. 

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• Prime the surface (if needed). Some membranes require a primer to improve adhesion. If a primer is necessary, apply it to the entire surface and allow it to dry completely.

• Apply the first coat. Use a roller, trowel, or sprayer to apply an even, consistent first coat of the waterproofing material.

• Apply subsequent coats. Once the first coat is dry, apply a second coat at a right angle to the first. Some products may require multiple coats to achieve the necessary thickness for submersion.

• Use mesh reinforcement. If you're using a fibrous mesh for extra crack resistance, apply it between the first and second coats. Smooth it firmly into the wet membrane to prevent air pockets. 

 

Step 3: Curing of the newly applied waterproofing

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The waterproofing membrane must be allowed to fully cure before the next step.

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• Follow manufacturer instructions. The required curing time varies depending on the product, temperature, and humidity. It can range from several days to a week or more.

• Control the environment. Avoid applying the membrane in direct sunlight, which can cause it to dry too quickly. It is also important to protect the newly applied membrane from rain or moisture during the curing period. 

 

Step 4: Leak testing 

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After the membrane has cured, a leak test, also known as a flood or ponding test, is essential to confirm the pool is watertight. 

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• Fill the pool gradually. Slowly fill the pool with water. To test for leaks more accurately, you can conduct phase testing by filling the pool in stages and monitoring the water level at each stage.

• Perform a controlled test. For the most accurate results, place a test vessel (like a bucket) with water next to the pool. The water level drop in the bucket accounts for evaporation. If the pool's water level drops significantly more than the bucket's, there is a leak.

• Make repairs if necessary. If a leak is detected, the pool must be drained to the level of the leak so it can be repaired before filling it again. 

 

Step 5: Tiling and grouting

 

Once the leak test is successful, you can proceed with the final finishes. 

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• Choose appropriate materials. Use a specialized, flexible tile adhesive and grout suitable for swimming pools, as these are formulated to withstand continuous water immersion and pool chemicals.

• Apply tiles. Lay the new tiles over the fully cured waterproofing membrane.

• Apply grout. After the adhesive has cured, apply the grout to the tile joints. Many pool-grade grouts are cementitious with added polymers for increased durability, while epoxy grouts offer excellent chemical resistance.

• Complete final curing. The pool should not be filled with water until the manufacturer's recommended curing time for both the adhesive and grout has passed. 

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The result is a watertight swimming pool interior that combines engineering precision with timeless luxury finishes.