Cementos Molins

Waterproofing a swimming pool

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Correct swimming pool waterproofing is essential and must not be overlooked to ensure that the facility operates optimally and has a long service life.

The reinforced concrete vessel made with formwork is the traditional system, although it is being used less often because the walls and floors are  built up separately and leaks may occur in the joining area.

The properties of the projected or gunited concrete are the most suitable for the construction of the vessel, since it allows to obtain a continuous wall, with greater resistance and smaller thickness, to support and to contain the pressure exerted by the ground, offering an optimum waterproofing thanks to the low porosity.

Full or empty, the pool vessel is always subjected to stresses such as hydrostatic water pressure and back pressure exerted by the ground.

To ensure impermeability in swimming pools, use PROPAM® IMPE FLEX (single component) or FLEXITEC (two-component) waterproofing mortars with high adhesion and flexibility for surface waterproofing, capable of withstanding the pressure and hydrostatic back pressure and movements produced by thermal shocks. If the PROPAM® IMPE FLEX mortar is used, proceed as follows.

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The substrate must be stable (wait a minimum of 28 days from the execution of the concrete element), and be clean of dust, paint, laitance, demoulding agents, etc.


Knead PROPAM® IMPE, PROPAM® IMPE FLEX or FLEXITEC with an electric mixer and with clean water until a lump free grout is obtained.

The substrate must be firm, flat and clean. Pre-fill voids and honeycombs with PROPAM® REPAR 40, PROPAM® REPAR 5, PROPAM® REPAR TECHNO or PROPAM® TAPAVÍAS.

Prior to application the substrate should be slightly moistened with water.

Apply a first layer on the surface, previously moistened, with a brush or roller in only one direction. Do not overextend the material.

After 4 hours, apply a second layer crosswise with respect to the first one.

Once PROPAM® IMPE FLEX is applied, it can be painted or coated with ceramics, using the appropriate tile adhesive of the PROPAMSA range.


  • Use the fiberglass mesh BETOFIBER GLASS between layers.
  • Wait a minimum of 4 days for the fixing of the tiles.
  • For the direct application of PROPAM® IMPE FLEX or FLEXITEC on an old vitreous mosaic coating, it is necessary to verify that the latter is well adhered to the base substrate and to perform an acid cleaning of its surface.
  • In order for the waterproofing system to work properly, the minimum thickness of PROPAM® IMPEFLEX or FLEXITEC must be 2 mm at any point.
  • Use FLEXITEC in waterproofings in which the required product is bicomponent.
  • In polyester pools, use VAT® ELASTIC for fixing the tiles



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