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Everything you need to know about swimming pool joint sealants. 

Understanding the Importance of Quality Sealants in Pool Maintenance

Swimming pool sealants safeguard domestic pools and wet areas within commercial spas and leisure facilities against water infiltration. These environments endure relentless wear and tear, necessitating joints that can withstand diverse challenges, from fluctuating temperatures to weather variations, moisture, condensation, and humidity.

Selecting the right sealant is important to ensuring a pool area's long-term safety and minimal maintenance.

Explore all the essential factors to consider when opting for a swimming pool sealant, encompassing the sealant type, application area, and compatible materials.


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The problem with swimming pool joints

Using the wrong sealant can be detrimental to the lifespan of a swimming pool or wet area. If water seeps behind the joints, or worse, freezes, it can damage tiles and turn into a costly repair job.

Ideally, the joints in swimming pools should be sealed with 100% silicone products that cure well under humidity and form a permanent elastic seal, with low shrinkage and no bubbles. Sealants should also be UV-resistant, flexible, and compatible with the environment they are being used in.

Bostik offers a wide range of professional swimming pool sealants suitable for both indoor and outdoor pools and other wet areas. To choose the best pool sealant for you, you must consider the following factors.

Factors to consider when choosing your swimming pool sealant

Durability and flexibility

Swimming pools and surrounding areas can be breeding grounds for mould, fungus, and bacteria due to the warm temperatures and humidity. Ensuring that your swimming pool is protected and remains low maintenance for years to come will depend on the properties of your sealant and how it is applied.

The best sealants for swimming pools must have:

  1. Very good water resistance
  2. High chlorine resistance
  3. Very good resistance to fungal attack
  4. Non-corrosive
  5. High elasticity and flexibility
  6. High durability

Plus, the unique formulas of Bostik’s best pool sealants give excellent gunning and tooling properties.

Above or below the water line?

Knowing if you need to work above or below the water line will affect which pool sealant you require. 

Areas above the water line experience frequent humidity and water ‘wear and tear’, but are not continuously submerged in water. This is the most common place to apply a Bostik swimming pool sealant. 

Sealing below the water line means sealing a joint that will be fully submerged in chlorinated water, continuously. When it comes to sealing swimming pool joints below the water line, we strongly advise you to contact our experts for the best product recommendations.


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Material and finish of your pool

It is important to understand how the material and finish will affect which sealant you require. We have neutral cure silicones available that are suitable for wet areas. Neutral cure silicone is non-staining on natural stones and non-corrosive for stainless steel. Sealants that include acetic acid cure can be corrosive to metals, so we recommend to always use neutral cure.

For sealing joints around ceramic tiles, natural stone or stainless steel above the water line, we recommend using our Bostik S765 Premium N

For sealing joints within PMMA above the water line, we recommend using our Bostik S780 Glass'N'Seal Premium.

How to prepare before applying a swimming pool sealant

Before you start sealing swimming pool joints, perform the following checks to ensure lasting results.

  • Check the substrates before purchasing your sealants. If you’re working with porous material like natural stone, then choose non-staining products to avoid discoloration.
  • For shiny, flat surfaces, a pure non-shrinking silicone sealant will give a better aesthetic finish.
  • Before applying any sealant, ensure the sides of the joint surface are clean, dry and free from contamination.
  • If you are renewing a sealant joint, ensure that all failed sealant is removed and that the surface is sound. Mechanical abrasion may be needed and primer can be considered to help prepare the surface.
  • For deep gaps in joints, a backer rod or foam piece should be used before applying the sealant.

Tips when applying a swimming pool sealant

One of the key areas of sealing is ensuring correctly sized fillet joints to help to ensure your wet area is fully waterproof.

Fillet joints are used to create a smooth transition between horizontal and vertical surfaces between adjacent walls. Due to the more severe conditions experienced in pools and wet areas, it is recommended that exposed fillet joints should have a face front of approximately 16mm, this gives 10mm of contact areas on wall to floor joints for a more robust seal.

Creating fillet joints correctly will help to reduce the risk of leaving an unsealed area, which could then be more likely to experience damage over time.

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Everything you need to know before sealing pool joints

Which sealant should you choose for the swimming pool area?

With joints within ceramic tiles, it is important to use a product that would offer good adhesion with ceramics as well as be able to resist humidity and water.  Sealants that contain 100% silicones with no dilutions will offer the best finish. They will form an elastic rubber seal when applied. You need a versatile sealant that cures under humidity and is mould free.

Natural stone tends to be porous and therefore is at a risk of getting stained or soiled at the edges. You need a non-staining silicone sealant.

Within PMMA (Polymethylmethacrylate) it is advisable to use a low modulus
silicone sealant. Ideally, one that is suitable for glazing applications and once cured, can withstand temperature fluctuations. You need a sealant that is suitable for PMMA and PC, which does not crack due to environmental stress.

When it comes to stainless steel in swimming pool areas, it is advisable to use a neutral silicone product that offers excellent adhesion. It also needs to be highly mould-resistant. You need a versatile silicone sealant that is non-corrosive to metals.

When sealing swimming pool joints below the water line, we strongly advise you to contact our experts to get the best product recommendations for your specific needs.


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Bostik ACADEMY is a knowledge center carefully created for professionals in the construction market. At the ACADEMY you can sign up for a tailored training program, matched to your needs and skills. 

Our experienced Technical Team will present our product portfolio, best application methods, and key industry recommendations. Sign up through the link below to learn more.


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