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Polyurea Swimming Pool Lining, London

THE PROBLEM

Aquascapes are a high end swimming pool design and installation contractor. They have developed innovative pool construction methods that offer significant improvements covering speed of construction, reduced structural load and reduced carbon dioxide emissions from construction.

One of the methods of swimming pool construction which they have developed makes use of high density expanded polystyrene modules that are assembled on site to form the pool structure.

These polystyrene modules are coated off site with a reinforced render prior to delivery on site and assembly. Watertightness had previously been achieved either using cementitious render systems or glass reinforced plastic – GRP/fibreglass. The GRP solution offers disadvantages such as odour and slow installation speed.

Aquascapes had worked with Mapei GB to develop an improved swimming pool lining methodology using their Polyurea material. Some of the key benefits this would offer included improved elasticity and speed of installation.

This site consisted of a Hydrotherapy pool and a larger swimming pool. The hydrotherapy consisted of many intricate details and nozzles.

Polyurea Swimming Pool 05

THE SOLUTION

Aquascapes own installers applied a Mapei approved fairing coat to the internal surfaces of the pool to provide a smooth and uniform surface suitable for polyurea application. A key consideration for this project was the uniformity of the finish as the pool would be finished post Polyurea application with mosaic tiles.

The polyurea waterproofing was also being extended into the concrete bund areas surrounding the pool, which were prepared by method of vacuum controlled diamond grinding. The same fairing coat was applied to the block walls to provide a uniform surface for polyurea application.

Anchor chases were cut in the blockwork in the bunded area and carefully around skimmer outlets in the pool – taking great care not to penetrate fully through the previously off site applied reinforced render.

Following climatic testing and monitoring of the substrate moisture content as part of our standard quality assurance all surfaces were primed using Mapei SN applied by method of brush and roller.

Polyurea Swimming Pool 06

The primer was applied in two coats as per our standard polyurea application process. The reason for this is that as polyurea is applied at 70 – 80 degrees centigrade and exotherms once mixed. The consequence of this is that any entrapped air within the substrate expands and causes pin holes if the substrate being coated is not fully sealed. The way to mitigate this as far as possible is to apply two coats of primer and ensure that the substrate temperature is either stable or falling.

The second coat of primer was fully blinded using a quartz aggregate to provide an excellent mechanical anchor for the subsequent polyurea membrane to adhere to. This also serves to remove the time restriction of the overcoat window, giving time to mask off items not to be coated etc.

Masking was in itself a significant task for this project, given the tight tolerance required for the waterproofing membrane around the extensive nozzles and penetrations in the hydrotherapy pool.

When applying polyurea you cannot use conventional masking tape, as the rapid gel time of the material (sub 8 seconds typically) means that the membrane forms over the tape and the high tensile properties of the polyurea make it extremely difficult to remove.

Instead a wire edged called Wiretrim is used at any termination points, which once spraying is complete is removed and cuts through the polyurea from the underside giving a neat edge.

Mapei Purtop 1000 was then spray applied using our own plural spray units to a minimum thickness of 2mm. All of our applicators are trained to the Polyurea Development Associations applicator course to ensure that this brilliant, but also potentially challenging material is applied correctly.

Because Mapei Purtop 1000 can elongate 300% it makes it particularly suitable for application to modular constructions such as these swimming pools.

The bunded areas were checked for porosity by method of DC Holiday spark testing as per our standard quality assurance. Because of the non conductive construction of the pools themselves this was not possible and a thorough visual inspection had to be undertaken.

The polyurea swimming pool linings were finished using an overspray method, which provided a light texture in order to promote adhesion of the subsequent epoxy tile adhesive.

Termination points both in the pools and the bunded areas were sealed using a mastic compound to ensure and seamless finish and protect the edge of the waterproofing membrane.

Within 48 hours of completion the pools were filled in order to conduct a leak/drop test. Again showing how the rapid curing properties of polyurea that as well as accelerating installation, also allow a quicker return to service than other systems employed in this area.