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Lining a swimming pool

Step by step instructions showing how to maintain and line your own swimming pool, presented by Crafty Corner

For any questions contact us via email

Pool preparation

If the pool has been previously painted then all the paint must be removed. This can be achieved in many ways, e.g. sand blasting, wire brush, sanding or paint remover. If paint remover is used care must be taken to ensure no residue remains to eliminate ant possibility of attack on the primer or on the laminate when those are applied to the stripped surface. Similarly all other contaminants such as algae, oily deposits, sand from sand blasting, general dirt and dirt introduced by cleaning must also be removed. The pool must be absolutely clean and free of any residue.


After the pool has been cleaned it must be inspected for defects such as cracks leaks and crumbling plaster. Repairs can be done using a cement grout or a polyester/sand mixture. The repaired surface must be sanded flush with surrounding surface.


All corners (wall to wall and steps) must be filled with a cement mortar and smoothed to a radius of at least 50 mm. This makes for easier application of the fibreglass liner and an improved liner to pool surface bond in these areas.

Removal of coping and mosaics

It is strongly recommended that coping stones and mosaics be removed. This enables the fibreglass liner to be carried under the coping stones and mosaics and results in a more reliable bond between the liner and the pool surface. Furthermore it prevents water seepage behind the fibreglass liner.
Once the coping stones and mosaics have been removed the area must be cleaned thoroughly.

Special considerations if the coping stones are not removed.

If the coping stones are not removed for any reason, then a horizontal groove must be cut as high as possible above the water level to receive and secure the top edge of the liner. This groove should ideally be dovetailed shape and at least 20 mm deep

Acid wash

Once all the repairs and corner modifications have been done and they are completely dry, the acid wash can commence. For old pools it is suggested that a 1% hydrochloric acid solution be used to wash all areas of the pool surface. For pools with new concrete of plaster a 5% hydrochloric acid solution should be used.

The purpose of an acid wash is to neutralise alkalinity on the surface of the concrete. When the pool has dried it must be washed thoroughly and allowed to completely dry. Polyester resin will not adhere to the pool surface if the surface is not completely dry, and the long term performance of the fibreglass lining. N.B. Be sure to wear protective clothing when applying the acid wash.

The primer layer

The primer layer should not be started if there is insufficient time available to commence laminating once the primer has gelled.

The surface area of the pool must be determined and sufficient resin obtained for a surface coverage of 300 / 400 g of resin /square meter. The resin must be divided into batches, each batch small enough to be applied within the working time of the resin once the catalyst has been added. The catalysed resin must be applied to the pool surface using a lamb’s wool roller. In order to keep the applied layer clean, it is best to start with the walls and then carry on to the floor working from the deep end to the shallow end so that the layer is not walked on. Once the primer has set then the next stage can start.

The fibreglass resin liner

Pigmented resin should not be used on the chopped strand mat as this will mask any air bubbles that must be removed.

Calculation of material quantities:
Chopped strand Mat 450g/m2 = 0.45kg/m2
Chopped strand Mat 300g/m2 = 0.30kg/m2
Surface Tissue 25g/m2 = 0.025 kg/m2

1) Mass of CSM (glass fibre mat) (kg) = (glass mass kg/m2) x (pool surface area, m2)
2) Mass of resin for the CSM = Total CSM mass (kg) x 3
3) Mass of surface Tissue = Total Tissue mass (kg) x pool surface area m2
4) Mass of resin for surface tissue = Total tissue mass x 10

All these amounts should be increased by 15% to allow for overlaps and wastage.

Application of the CSM liner

The pool area must be divided into sections each of which can easily be covered with CSM, well within the expected gel time of the resin batch.

It should be noted that the gel time of the resin is dependant on the prevailing temperature (surrounding air and concrete) and the amount of catalyst used.
The catalyst content can be varied to alter the gel time at different temperatures but should be kept between 1% and 2%.
The CSM should be cut to fit one of these sections and then weighed. The correct amount of resin is then weighed and catalysed. (Resin mass = 3 x CSM mass).

Where coping stones have been removed, application of the CSM must start in a groove 20 – 30 mm deep cut into the coping substrate at least 120mm in from the edge of the pool, and progress down the wall towards the floor.
About 80% of the resin should be applied evenly to the pool surface, followed by the CSM.
The CSM must then be rolled with an aluminium laminating roller ensure the consolidation of the laminate and to remove voids. Additional resin can be added to obvious dry spots and these must be worked to ensure full wet out of the fibres.
The next section is applied in the same manner, as the first but overlaps the previous layer. The next layer (if required) is applied in the same way before the 1st layer starts gelling, but it must centrally straddle the overlap formed in the 1st layer.
This final layer is followed by the surface tissue, which must be thoroughly wetted out with the resin.

Once the walls are complete the CSM is applied to the floor, also in sections. Care must be taken to ensure that the working area is kept clean.
The steps are lined last and an additional layer of CSM can be applied here.
Any joints must overlap by at least 50mm.

Special considerations if the coping stones have not been removed

The groove cut for securing the laminate must first be covered with appropriately large quantities of catalysed resin. The top edge of the CSM must then be laid into the groove and worked to ensure complete wet out. The groove must then be sealed with a mixture of catalysed resin and silica powder.

Inspection and repair

The Fibre glass liner should be allowed to gel and then carefully inspected for irregularities and defects such as, dry spots, exposed fibres, etc. If the inspection is satisfactory the top coat can be applied

This should be done as soon as possible after the liner has been completed, to ensure a good bond. If repairs are necessary, these areas after repairs should be allowed to cure and then be sanded flush with the surrounding laminate. If the liner has been left for an extended period and the resin is fully cured, it will be necessary to sand the total area to ensure good adhesion of the pool coat.

Application of the pool coat

It is suggested that white or pale colours are chosen as dark coloured poolcoats can discolour in patches when in contact with water. The Poolcoat is catalysed so as to afford a reasonable gel time at the prevailing temperature.

It must be stirred thoroughly and then applied in a single even coating at 500 – 600 g/m2. The Poolcoat must be allowed for approximately 24 hours before inspection. If repairs are necessary, the area must be sanded to remove the wax layer and then recoated using the recommended amount of Poolcoat and catalyst.

Filling the completed pool

Before the pool is filled with water, the liner and Poolcoat must be given sufficient time to cure completely. If this is not done the liner will be more susceptible to moisture attack, de-bonding and cracking.

In summer 5-6 days should be allowed between completion of the pool and filling it with water. In winter, the cure period should be further extended depending on ambient temperatures.

Replacing coping stones

If coping stones were removed during construction of the fibreglass liner, they can be replaced once the Poolcoat has cured.
The Poolcoat should be sanded in the areas where the coping stones are to be locater, to remove the wax layer on the surface.
The stones can be fixed with an epoxy or urethane adhesive. Once the adhesive has set the spaces between the stones can be filled with standard tile cement.

General Points

Construction of a swimming pool liner should not be started if there is a possibility of rain, since each phase of the process should be continuous until completed.
If insufficient time is available to allow completion of a particular phase, that phase should not be started.
It is recommended that no work takes place if the air temperature is below 15 deg C.
Suitable safety goggles, protective clothing, and a dust mask should always be used when sanding a GRP laminate.
The finished liner should be smooth, with all edges sealed properly, and there must be no exposed fibres or sharp edges.
When the pool is used after lining, the pH value of the water should be maintained at 7 at all times. Pool care additives such as chorine of acids should always be added in diluted form.